Penting Buat Petani Sehat (LEPTOSPIROSIS)

sebikit catatan yang berkaitan untuk petani kita, yang mau baca silahkan,,,,,,,,,

Apakah Leptospirosis itu?

Leptospirosis adalah penyakit yang dialami manusia dan hewan, yang disebabkan oleh kuman leptospira. Kuman ini ditemukan dalam air seni dan sel-sel hewan yang terkena. Angka kematian leptospirosis ini tergolong cukup tinggi. Di Indonesia mencapai 16,45%, bahkan untuk usia di atas 50th mencapai 56%.

Binatang apa saja yang umumnya terkena?

Berbagai bintang menyusui bisa mengidap kuman leptospira, yang paling sering adalah jenis tikus, anjing, binatang kandang seperti kandang dan sapi, babi, kuda, kucing dan domba. Binatang yang terkena mungkin sama sekali tifak memiliki gejala atau tampak sehat wal afiat.

Apa Saja gejala penyakit Leptospirosis?

Gejala dini Leptospirosis umumnya adalah demam, sakit kepala berat, nyeri otot, gerah, muntah dan mata merah. Aneka gejala ini bisa menyerupai gejala penyakit lain seperti flu, sehingga menyulitkan penegakkan diagnosis. Bahkan ada penderita yang mengalami gejala tersebut.

Ada penderita Leptospirosis yang lebih lanjut mengalami penyakit yang parah, termasuk yang disebut dengan "penyakit weil", sakit kuning (menguningnya kulit yang menandakan penyakit hati) dan pendarahan pada kulit dan selaput lendir.

Pembengkakan selaput otak atau meningitis dan pendarahan paru-paru pun terjadi. Kebanyakan penderita yang sakit parah memerlukan rawat inap. Leptospirosis yang parah terkadang dapat merenggut nyawa.

Apa Dampak Jangka panjang?

Penyembuhan penyakit leptospirosis ini bisa lambat. Ada yang mengalami sakit mirip kelelahan menahun selama berbulan-bulan. Ada pula yang terus mengalami sakit kepala atau perasaan tertekan. Adanya kalanya kuman ini bisa terus berada di dalam mata dan menyebabkan bengkak mata menahun.

Bagaimana cara tersebarnya kuman?

Kuman leptospira biasanya memasuki tubuh lewat luka atau lecet kulit. Kadang-kadang pula melalui selaput di dalam mulut, hidung dan mata. Berbagai jenis binatang bisa mengidap kuman leptospira di dalam ginjalnya. Penularannya bisa terjadi setelah tersentuh air kencing hewan itu atau tubuhnya. Tanah, lumpur, atau air yang dicemari air kencing hewan pun dapat menjadi sumber infeksi. Makanan-makanan atau minuman air yang tercemar dapat juga menjadi perantaraan penularan penyakit.

Nah bagian ini yang berhubungan sama petani

Siapa yang menghadapi resiko tertular?

Manusia yang mempunyai resiko adalah mereka yang sering menyentuh BINATANG atau AIR, LUMPUR, TANAH dan TANAMAN yang telah dicemari air kencing binantang. Beberapa pekerjaan yang memang lebih berisiko misalnya PEKERJAAN PETANI, DOKTER HEWAN, KARYAWAN PENJAGALAN, SERTA PETANI TEBU DAN PISANG.

Aneka hobi yang bersentuhan dengan air atau tanah yang tercemar pun bisa menularkan leptospirosis, misalnya berkemah, berkebun, berkelana di hutan, berakit di air, arung jeram dan olah raga air lainnya.

Bagaimana cara mencegah leptospirosis?

Ada banyak cara mencegah leptospirosis diantaranya;

• yang pekerjaannya berhubungan dengan bintang:

-Tutupilah setiap luka/ lecet/ kutu air dengan pembalut yang kedap air

-Gunakan pelindung, misalnya sarung tangan, pelindung mata, jubah kain dan sepatu bila mengangani binatang yang mungkin terkena leptospira, terutama jika da kemungkinan menyentuh air seninya.

-Pakailah sarung tangan jika mengangani ari-ari hewan, janinnya yang mati di dalam maupun digugurkan atau menyentuh dagingnya.

-Mandilah sesudah bekerja dan cucilah dengan sabun serta keringkan tangan setelah menangani apapun yang mungkin terkena leptospira

-Ikutilah anjuran dokter hewan ketika memberi vaksin pada hewan.

• Untuk yang lain:

-Hindari berenang di dalam air yang mungkin di cemari air seni binatang (yang anak desa suka mandi di kali, hati-hati ya!! hihihi)

-Tutupilah luka dan lecet dengan balutan kedap air terutama sebelum bersentuhan dengan air tanah, lumpur atau air yang mungkin dicemari air kencing binatang

-Pakailah sepatu apabila keluar rumah, terutama jika tanahnya basah atau berlumpur

-Pakailah sarung tangan bila berkebun

-Halaulah binatang pengerat/tikus dengan cara membersihkan dan menjauhkan sampah dari rumah

-Jangan memberi anjing/kucing jeroan mentah

-Cuci tangan dengan sabun karena kuman leptospira cepat mati oleh sabun (Cuci tangan penting lho! buat yang suka jorok, ati-ati ya, hehehe)

Bagaimana jika saya sampai jatuh sakit?

Segera ke dokter jika anda jatuh sakit setelah ada kemungkinan terkena air seni binatang atau berada di lingkungan yang mungkin terserang wabah LEPTOSPIROSIS.

oyaa, perlu diketahui kalu Leptospirosis itu adalah bakteri bukan virus.

oke, cukup sampe disini ya, makasih buat yang uda mw baca. maaf kalo banyak kekurangannya. ^^/

Roles of Soil Biota In P-transformation

A.  INTRODUCTION

Healthy soil is the foundation of the food system. It produces healthy crops that in turn nourish people. Maintaining a healthy soil demands care and effort from farmers because farming is not benign. By definition, farming disturbs the natural soil processes including that of nutrient cycling – the release and uptake of nutrients.

Soil is a living, dynamic ecosystem. Healthy soil is teeming with microscopic and larger organisms that perform many vital functions including converting dead and decaying matter as well as minerals to plant nutrients. Different soil organisms feed on different organic substrates. Their biological activity depends on the organic matter supply.

The soil biota consist of a large number and range of micro- and macro-organisms and are the living part of soils. They interact with each other and with plants, directly providing nutrition and other benefits. They regulate their own populations as well as those of incoming microorganisms by biological control mechanisms. Microorganisms are responsible for organic matter decomposition and for the transformations of organically bound nitrogen and minerals to forms that are available to plants. Their physical structure and products contribute significantly to soil structure. Management practices have a significant impact on micro- and macro-organism populations and activities.

Phosphorus (P) is one of the major plant growth-limiting nutrients although it is abundant in soils in both inorganic and organic forms. Phosphate solubilizing micro-organisms (PSMs) are ubiquitous in soils and could play an important role in supplying P to plants in a more environmentally friendly and sustainable manner. Although solubilization of P compounds by microbes is very common under laboratory conditions, results in the field have been highly variable.

B.  DISCUSSION

P in soils is present in pools varying in availability, and pools with the lowest availability are the largest in Oxisols. The quantity of P present in the soil solution represents only a small fraction of plant needs, and the remainder must be obtained from the solid phase by a combination of abiotic and biotic processes. The processes involved in soil P transformation are precipitation- dissolution and adsorption-desorption which control the abiotic transfer of P between the solid phase and soil solution, and biological immobilization-mineralization processes that control the transformations of P between inorganic and organic forms.

With increasing demand of agricultural production and as the peak in global production will occur in the next decades, phosphorus (P) is receiving more attention as a nonrenewable resource. One unique characteristic of P is its low availability due to slow diffusion and high fixation in soils. All of this means that P can be a major limiting factor for plant growth. Applications of chemical P fertilizers and animal manure to agricultural land have improved soil P fertility and crop production, but caused environmental damage in the past decades. Maintaining a proper P-supplying level at the root zone can maximize the efficiency of plant roots to mobilize and acquire P from the rhizosphere by an integration of root morphological and physiological adaptive strategies. Furthermore, P uptake and utilization by plants plays a vital role in the determination of final crop yield. Taken together, overall P dynamics in the soil-plant system is a function of the integrative effects of P transformation, availability, and utilization caused by soil, rhizosphere, and plant processes.

Soil P exists in various chemical forms including inorganic P (Pi) and organic P (Po). These P forms differ in their behavior and fate in soils. Pi usually accounts for 35% to 70% of total P in soil. Primary P minerals including apatites, strengite, and variscite are very stable, and the release of available P from these minerals by weathering is generally too slow to meet the crop demand though direct application of phosphate rocks (i.e. apatites) has proved relatively efficient for crop growth in acidic soils. In contrast, secondary P minerals including calcium (Ca), iron (Fe), and aluminum (Al) phosphates vary in their dissolution rates, depending on size of mineral particles and soil. With increasing soil pH, solubility of Fe and Al phosphates increases but solubility of Ca phosphate decreases, except for pH values above 8. The P adsorbed on various clays and Al/Fe oxides can be released by desorption reactions. All these P forms exist in complex equilibria with each other, representing from very stable, sparingly available, to plant-available P pools such as labile P and solution P.

In acidic soils, P can be dominantly adsorbed by Al/Fe oxides and hydroxides, such as gibbsite, hematite, and goethite. P can be first adsorbed on the surface of clay minerals and Fe/Al oxides by forming various complexes. The nonprotonated and protonated bidentate surface complexes may coexist at pH 4 to 9, while protonated bidentate innersphere complex is predominant under acidic soil conditions. Clay minerals and Fe/Al oxides have large specific surface areas, which provide large number of adsorption sites. The adsorption of soil P can be enhanced with increasing ionic strength. With further reactions, P may be occluded in nanopores that frequently occur in Fe/Al oxides, and thereby become unavailable to plants.

In neutral-to-calcareous soils, P retention is dominated by precipitation reactions, although P can also be adsorbed on the surface of Ca carbonate and clay minerals. Phosphate can precipitate with Ca, generating dicalcium phosphate (DCP) that is available to plants. Ultimately, DCP can be transformed into more stable forms such as octocalcium phosphate and hydroxyapatite (HAP), which are less available to plants at alkaline pH. HAP accounts for more than 50% of total Pi in calcareous soils from long-term fertilizer experiments (H. Li, personal communication). HAP dissolution increases with decrease of soil pH, suggesting that rhizosphere acidification may be an efficient strategy to mobilize soil P from calcareous soil.

Po generally accounts for 30% to 65% of the total P in soils. Soil Po mainly exists in stabilized forms as inositol phosphates and phosphonates, and active forms as orthophosphate diesters, labile orthophosphate monoesters, and organic polyphosphates. The Po can be released through mineralization processes mediated by soil organisms and plant roots in association with phosphatase secretion. These processes are highly influenced by soil moisture, temperature, surface physical-chemical properties, and soil pH and Eh (for redox potential). Po transformation has a great influence on the overall bioavailability of P in soil. Therefore, the availability of soil P is extremely complex and needs to be systemically evaluated because it is highly associated with P dynamics and transformation among various P pools.

Better understanding of P dynamics in the soil/rhizosphere-plant continuum provides an important basis for optimizing P management to improve P-use efficiency in crop production. The effective strategies for P management may involve a series of multiple-level approaches in association with soil, rhizosphere, and plant processes. P input into farmland can be optimized based on the balance of inputs/outputs of P. Soil-based P management requires a long-term management strategy to maintain the soil-available P supply at an appropriate level through monitoring soil P fertility because of the relative stability of P within soils. By using this approach, the P fertilizer application can be generally reduced by 20% compared to farmer practice for the high-yielding cereal crops in the North China. This may be of significant importance for saving P resources without sacrificing crop yields though it may cause P accumulation in soil due to high threshold levels and low P-use efficiency by crops.

C.  CONCLUSIONS

Phosphorus losses from soils occur by leaching at very low rates in undisturbed. The implementation of  intensive agricultural production has markedly increased P losses from soils through increased runoff, erosion and leaching, which in turn can have adverse effects on water quality. These losses are further increased by the excessive accumulation of bioavailable P in the upper soil horizons, due either to application of inorganic and/or organic P fertilizers in excess of plant needs and/or to inappropriate fertilizer applications.

The P nutrition of plants is predominantly controlled by P dynamics in the soil/rhizosphere-plant continuum. The distribution and dynamics of P in soil has a significant spatio-temporal variation. Root architecture that distributes more roots to the place where P resources are located plays an important role in efficiently exploiting these P resources. Furthermore, root architecture can exhibit functional coordination with root exudation of carboxylates, protons, and phosphatases in P mobilization and acquisition. The coordination of plant adaptations in root morphology and root physiology to P-limiting environments may effectively match heterogeneous P supply and distribution in soil, resulting in increased spatial availability and bioavailability of soil P. The integration of P dynamics from soil to plant via the rhizosphere provides a comprehensive picture of available P behavior and efficient acquisition in association with plant adaptive strategies. In the past two decades, significant progress has been made in understanding soil, rhizosphere, and plant processes associated with soil P transformation, P mobilization and acquisition, and P-deficiency responses.

Given the importance of P to plants and its importance as a strategic resource, a better understanding of P dynamics in the soil/rhizosphere-plant continuum is necessary to guide establishment of integrated P-management strategies involving manipulation of soil and rhizosphere processes, development of P-efficient crops, and improving P-recycling efficiency.

BIBLIOGRAPHY

Bot, Alexandra. and Jose Benites. 2005. The Importance of Soil Organic Matter. Food and Agriculture Organization of The United Nations (FAO). Rome, Italy. ftp://ftp.fao.org/agl/agll/docs/sb80e.pdf

Cardoso, Irene M. and Thomas W. 2006. Kupyer. Mychorrhizas and tropical soil fertility. Agriculture, Ecosystems and Environment 116 (2006) 72–84. http://dels-old.nas.edu/banr/gates1/docs/mtg5docs/bgdocs/mycorrhizas_tropical_soil.pdf

Frossard, et al. 2000. Processes Governing Phosphorus Availability in Temperate Soils. J. Environ. Qual. 29:15-23. http://researcharchive.lincoln.ac.nz/dspace/bitstream/10182/1134/1/Temperate_Soils.pdf

Gyaneshwar, et al. 2002. Role of soil microorganisms in improving P nutrition of plants. Journal of Plant and Soil. Volume 245, Number 1 (2002), 83-93, DOI: 10.1023/A:1020663916259. http://www.springerlink.com/content/g0710v2x185727kp/

Roper, MM. and V Gupta. 2012. Management-practices and soil biota. Australian Journal of Soil Research 33(2) 321 – 339. http://www.publish.csiro.au/paper/SR9950321.htm

Shen, et al. 2011. Phosphorus Dynamics: From Soil to Plant. Plant Physiology July 2011 vol. 156 no. 3 997-1005. http://www.plantphysiol.org/content/156/3/997.full

THE PROCESS OF SEED GERMINATION

A.    INTRODUCTION

            Most plants life starts from the humble seed, leaf through this article to understand the seed germination process. Life begins from the seed for all plants alike. To reproduce itself and evolve with time is what a seed offers to the eco-system, and many trees, plants and flowers bear witness to this fact. A seed is basically a kernel that encloses in itself a small embryonic plant covered by a hard seed coat and some stored food that upon receiving the appropriate climatic conditions, will promote growth. The seed is the ripened ovule, (egg) fertilized product of gymnosperm and angiosperm plants. This is the end product of the pollination process in which the embryo develops from the zygote, and the seed coat from the outer covering of the ovule. The ability to consistently and successfully reproduce itself makes trees and plants that use their seeds for propagating themselves have a higher survival rate, than the ones who rely on cuttings, runners, shoots or rhizomes. Let us understand this amazing ability by reading through the seed germination process.

            Germination is the growth of an embryonic plant contained within a seed; it results in the formation of the seedling. The seed of a vascular plant is a small package produced in a fruit or cone after the union of male and female sex cells. All fully developed seeds contain an embryo and in most plant species some store of food reserves, wrapped in a seed coat. Some plants produce varying numbers of seeds that lack embryos; these are called empty seeds and never germinate. Most seeds go through a period of dormancy where there is no active growth; during this time the seed can be safely transported to a new location and/or survive adverse climate conditions until circumstances are favorable for growth. Dormant seeds are ripe seeds that do not germinate because they are subject to external environmental conditions that prevent the initiation of metabolic processes and cell growth. Under favorable conditions, the seed begins to germinate and the embryonic tissues resume growth, developing towards a seedling.

B.     DISCUSSION

            Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the growth of hyphae from fungal spores, is also germination. In a more general sense, germination can imply anything expanding into greater being from a small existence or germ.

            Seeds remain dormant or inactive until conditions are right for germination. All seeds need water, oxygen, and proper temperature in order to germinate. Some seeds require proper light also. Some germinate better in full light while others require darkness to germinate.

            When a seed is exposed to the proper conditions, water and oxygen are taken in through the seed coat. The embryo's cells start to enlarge. Then the seed coat breaks open and a root or radicle emerges first, followed by the shoot or plumule that contains the leaves and stem.

            Many things can cause poor germination. Overwatering causes the plant to not have enough oxygen. Planting seeds too deeply causes them to use all of their stored energy before reaching the soil surface. Dry conditions mean the plant doesn't have enough moisture to start the germination process and keep it going.

            Some seed coats are so hard that water and oxygen cannot get through until the coat breaks down. Soaking or scratching the seeds will help break down the seed coat. Morning glories and locust seeds are examples. Other seeds need to be exposed to proper temperatures. Apple seeds will not germinate unless they are held at cold temperatures for a period of time.

            The seed contains an immature plant (embryo) that resembles an adult plant, complete with leaves and a root. The seed's leaves are called the cotyledons, seeds that contain one embryonic leaf are known as monocotyledonous or monocots, whereas seeds with two embryonic leaves are termed as dicotyledonous or dicots. The food found in the seed which nourishes the embryonic seedling during its early stages of development, is known as endosperm.
            There are certain basic steps of seed germination. For a seed to germinate successfully, firstly, the right conditions are required. Although, most seeds will germinate under different conditions, the plants or trees will not come true, as it's the quality of the seed that matters, not its age. Lotus seeds as old as 2000 years have germinated, as the quality of their embryo was preserved. Moisture or water is needed by the dried seeds to resume their cellular metabolism and growth. Moisture, combined with warmth, triggers growth, which is probably the reason why sown seeds should be kept in a warm place. Warmth increases humidity, which ensures enough moisture to the seeds. The size of the seed and the depth it is sowed in determines how quick it will sprout through the soil. The larger the seed, more the energy stored in it, and vice-versa. This is the reason why large seeds are sowed more deeper in comparison to smaller seeds. Soil matters as the seed takes its oxygen from its pores, and the right temperature will accelerate its growth. Whether a seed needs light, full or partial, or darkness to sprout depends upon its individual physiological need. The dormancy level of the seeds also determines the time it will take to germinate. Another way to germinate seeds is by growing seeds without soil.

            Once the conditions have been satisfied for the process of seed germination, it is just a matter of time that they turn into a seedling. Some seeds, especially the ones with hard coats like the sunflower, morning glory, dates, acorn, corn, etc. need a couple of hours pre-soaking to speed up the germination of seeds.

            After the seeds are sowed, and the soil misted with water, it (water) gets absorbed by the seeds through its coat, and provides moisture to the embryo nestled in it. This activates enzymes that help in duplication of plant cells, and also gets them to use the energy or food stored in the seed to start nourishing the embryonic plant. With all the nourishment, the embryo becomes too large, and bursts open through the seed coat, in search of light to start its process of photosynthesis, and thus, the growing plant emerges. During the same time, even the roots sprout and head down in search of more food from the soil. Both the root and plant shoot move downwards and upwards, simultaneously and respectively. In no time then, you will see the seedling force its way through the soil.

There are basically three steps of seed germination:

• Step 1-Water imbibation results in rupture of seed coat, uniform imbibation is important and approximately optimum temperatures are required
• Step 2-The imbibition of the seed coat results in emergence of the radicle and the plumule, the cotyledons get unfolded. It is important that the temperature and photo period are required in optimum amounts
• Step 3-This marks the final step in the germination of the seed where the cotyledons are expanded which are the true leaves.

Factors affecting seed germination 

            Seed germination depends on both internal and external conditions. The most important external factors include temperature, water, oxygen and sometimes light or darkness. Various plants require different variables for successful seed germination. Often this depends on the individual seed variety and is closely linked to the ecological conditions of a plant's natural habitat. For some seeds, their future germination response is affected by environmental conditions during seed formation; most often these responses are types of seed dormancy.

• Water - is required for germination. Mature seeds are often extremely dry and need to take in significant amounts of water, relative to the dry weight of the seed, before cellular metabolism and growth can resume. Most seeds need enough water to moisten the seeds but not enough to soak them. The uptake of water by seeds is called inbibition, which leads to the swelling and the breaking of the seed coat. When seeds are formed, most plants store a food reserve with the seed, such as starch, proteins, or oils. This food reserve provides nourishment to the growing embryo. When the seed imbibes water, hydrolytic enzymes are activated which break down these stored food resources into metabolically useful chemicals. After the seedling emerges from the seed coat and starts growing roots and leaves, the seedling's food reserves are typically exhausted; at this point photosynthesis provides the energy needed for continued growth and the seedling now requires a continuous supply of water, nutrients, and light.

• Oxygen - is required by the germinating seed for metabolism. Oxygen is used in aerobic respiration, the main source of the seedling's energy until it grows leaves. Oxygen is an atmospheric gas that is found in soil pore spaces; if a seed is buried too deeply within the soil or the soil is waterlogged, the seed can be oxygen starved. Some seeds have impermeable seed coats that prevent oxygen from entering the seed, causing a type of physical dormancy which is broken when the seed coat is worn away enough to allow gas exchange and water uptake from the environment.

• Temperature - affects cellular metabolic and growth rates. Seeds from different species and even seeds from the same plant germinate over a wide range of temperatures. Seeds often have a temperature range within which they will germinate, and they will not do so above or below this range. Many seeds germinate at temperatures slightly above room-temperature 60-75 F (16-24 C), while others germinate just above freezing and others germinate only in response to alternations in temperature between warm and cool. Some seeds germinate when the soil is cool 28-40 F (-2 - 4 C), and some when the soil is warm 76-90 F (24-32 C). Some seeds require exposure to cold temperatures (vernalization) to break dormancy. Seeds in a dormant state will not germinate even if conditions are favorable. Seeds that are dependent on temperature to end dormancy have a type of physiological dormancy. For example, seeds requiring the cold of winter are inhibited from germinating until they take in water in the fall and experience cooler temperatures. Four degrees Celsius is cool enough to end dormancy for most cool dormant seeds, but some groups, especially within the family Ranunculaceae and others, need conditions cooler than -5 C. Some seeds will only germinate after hot temperatures during a forest fire which cracks their seed coats; this is a type of physical dormancy.

        Most common annual vegetables have optimal germination temperatures between 75-90 F (24-32 C), though many species (e.g. radishes or spinach) can germinate at significantly lower temperatures, as low as 40 F (4 C), thus allowing them to be grown from seed in cooler climates. Suboptimal temperatures lead to lower success rates and longer germination periods.

• Light or darkness - can be an environmental trigger for germination and is a type of physiological dormancy. Most seeds are not affected by light or darkness, but many seeds, including species found in forest settings, will not germinate until an opening in the canopy allows sufficient light for growth of the seedling.

            Scarification mimics natural processes that weaken the seed coat before germination. In nature, some seeds require particular conditions to germinate, such as the heat of a fire (e.g., many Australian native plants), or soaking in a body of water for a long period of time. Others need to be passed through an animal's digestive tract to weaken the seed coat enough to allow the seedling to emerge.

Germination rate

            In agriculture and gardening, the germination rate describes how many seeds of a particular plant species, variety or seedlot are likely to germinate. It is usually expressed as a percentage, e.g., an 85% germination rate indicates that about 85 out of 100 seeds will probably germinate under proper conditions. The germination rate is useful for calculating the seed requirements for a given area or desired number of plants.

Dicot germination

The part of the plant that first emerges from the seed is the embryonic root, termed the radicle or primary root. It allows the seedling to become anchored in the ground and start absorbing water. After the root absorbs water, an embryonic shoot emerges from the seed. This shoot comprises three main parts: the cotyledons (seed leaves), the section of shoot below the cotyledons (hypocotyl), and the section of shoot above the cotyledons (epicotyl). The way the shoot emerges differs among plant groups.

Epigeous

In epigeous (or epigeal) germination, the hypocotyl elongates and forms a hook, pulling rather than pushing the cotyledons and apical meristem through the soil. Once it reaches the surface, it straightens and pulls the cotyledons and shoot tip of the growing seedlings into the air. Beans, tamarind, and papaya are examples of plants that germinate this way.

Hypogeous

Another way of germination is hypogeous (or hypogeal), where the epicotyl elongates and forms the hook. In this type of germination, the cotyledons stay underground where they eventually decompose. Peas, for example, germinate this way.

Monocot germination

In monocot seeds, the embryo's radicle and cotyledon are covered by a coleorhiza and coleoptile, respectively. The coleorhiza is the first part to grow out of the seed, followed by the radicle. The coleoptile is then pushed up through the ground until it reaches the surface. There, it stops elongating and the first leaves emerge.

Precocious germination

While not a class of germination, precocious germination refers to seed germination before the fruit has released seed. The seeds of the green apple commonly germinate in this manner.

One-step seed germination of Brassica and pea seeds: testa rupture and initial radicle elongation

• The endosperm is completele obliterated during the seed development of Brassica spp. (see figure below) or pea and the mature seeds of these species are therefore non-endospermic. Uptake of water by a seed is triphasic with a rapid initial uptake (phase I, i.e. imbibition) followed by a plateau phase (phase II). A further increase in water uptake (phase III) occurs only when germination is completed, as the embryo axes elongates and breaks through the testa. Thus, besides radicle elongation, testa rupture is the only visible landmark during Brassica spp. and pea seed germination.
• Abscisic acid (ABA) does not inhibit imbibition and testa rupture (see figure below), but ABA inhibits phase III water uptake and the transition from germination to postgermination growth.

Brassica napus seed germination is one-step. The mature seeds of these species are without endosperm and so testa rupture plus initial radicle elongation result in the completion of germination. ABA does not inhibit testa rupture, but inhibits subsequent radicle growth.

Two-step seed germination of Lepidium and Arabidopsis (Brassicaceae): testa and endosperm rupture

• For the Lepidium and Arabidopsis seed anatomy see the webpage "Seed Structure".
• Rupture of the testa (seed coat) and rupture of the endosperm are separate events in the germination of Lepidium and Arabidopsis seeds (see figures below). Arabidopsis and Lepidium exhibit a two-step germination, in which testa rupture and endosperm rupture are sequential events. 

• Such two-step germination is widespread over the entire phylogenetic tree and has been described for many species, e.g. for Trollius, Chenopodium, Nicotiana and Petunia.
• We found that the plant hormone ABA inhibits endosperm rupture, but not testa rupture, of Arabidopsis and Lepidium. This inhibitory effect of ABA is counteracted by GA, supporting the view that endosperm rupture is under the control of an ABA-GA antagonism.
• We found that ABA inhibits endosperm weakening of Lepidium, and this inhibitory effect is counteracted by GA. This supports the view that weakening of the micropylar endosperm occurs in Arabidopsis and Lepidium seeds (Brassicaceae, Rosid clade), is under ABA-GA control, and is functioning in controlling the germination of endospermic Brassicaceae seeds.
• We show that ethylene promotes endosperm cap weakening of Lepidium sativum and endosperm rupture of the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle shows that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target. Ethylene counteracts the ABA-induced inhibition without affecting seed ABA levels. The Arabidopsis loss-of-function mutants ACC oxidase2 (aco2; ethylene biosynthesis) and constitutive triple response1 (ctr1; ethylene signaling) are impaired in the 1-aminocyclopropane-1-carboxylic acid (ACC)-mediated reversion of the ABA-induced inhibition of seed germination. Ethylene production by the ACC oxidase orthologs Lepidium ACO2 and Arabidopsis ACO2 appears to be a key regulatory step. Endosperm cap weakening and rupture are promoted by ethylene and inhibited by ABA to regulate germination in a process conserved across the Brassicaceae.

C.    CONCLUSION

            Germination is a fascinating process. Seeing a tiny seedling emerge from a dry, wrinkled seed and watching its growth and transformation, is observing the mystery of life unfolding. The first sign of germination is the absorption of water until lots of water. This activates an enzyme, respiration increases and plant cells are duplicated. Soon the embryo becomes too large, the seed coat bursts open and the growing plant emerges. The tip of the root is the first thing to emerge and it's first for good reason. It will anchor the seed in place, and allow the embryo to absorb water and nutrients from the surrounding soil.

            Some seeds need special treatment or conditions of light, temperature, moisture, etc. to germinate. Seed dormancy is very complex, but it protects that living plant material until conditions are right for it to emerge and grow.

            For the growth and development of seeds ,different kinds of food like carbohydrates, fats and proteins are required in stored form. Besides the growth promoting substances like auxins, heteroauxins are also formed at the time of germination which controls the growth and development of seedlings during germination.

REFERENCES

Anonim^a. 2012. Germination. en.wikipedia.org/wiki/Germination.

Anonim^b. 2012. Germination. http://urbanext.illinois.edu/gpe/case3/c3facts3.html

Buzzle. 2012. Seed Germination Process. http://www.seedbiology.de/germination.asp

Kennel, Holly S. 2012. Seed Germination. gardening.wsu.edu/library/.../vege004.htm

Koning, Ross. 2012. Seed Germination. www.seedbiology.de/germination.asp

Leubner, Gerhard. 2011. Seed Germination. http://plantphys.info/seedg/seed.html

Tutorvista. 2010. Process of Seed Germination. http://www.tutorvista.com/content/biology/biology-iv/plant-growth-movements/seed-germination-process.php

Problem and Solve of Seed Technology

PRELIMINARY

About one million hectares (2.47 million acres) in the Tropics are planted in tree seedlings each year, but only a small portion of these seedlings are indigenous species. A common barrier to the use of indigenous species is the unavailability of high-quality seeds arising from the lack of seed technology information. Seed problems of tropical forest trees that need more study include phenology of flowering and fruiting, collection, cleaning, storage, and pretreatment for germination. A number of capable research centers around the world are working to find the answers.

Fruit is a matured or ripened ovary which contains one or more ovules that develop into seed. Botanically seed is defined as matured (after fertilization) and ripened ovule which contains an embryo with food reserve and protective coat. As per seed technology or agriculture seed is a plant part which is used for raising or propagation or multiplication of commercial crops e.g. true seed, tubers, suckers, bulbs, cuttings, setts and grafts.

Progress of agriculture depends on production and distribution of good quality seeds, of best yielding varieties with favorable characteristics. At the same time quality of agriculture depends on good quality seed. Seed technology takes care of this.

In simple words, seed technology is the science dealing with the methods of improving physical and genetical characteristics of seed. The various aspects coming under seed technology are seed production, seed processing, seed certification, seed testing, seed storage, seed biology, seed entomology, seed pathology and seed marketing.

Prerequisite for any seed production program is to maintain genetic purity and other characteristics of seed. Therefore seed production should be conducted with some underlying principles. Seed technology categories such principles considered during production and seed multiplication under two main headings.

Seed production is organized process. Different stages during the process ensure that seed multiplied at each stage meet all seed certification standards for that hybrid or crop variety. Various stages of seed multiplication are as follows.

Seeds are the delivery systems for agricultural biotechnology. High quality seed leads to excellent seedling performance in the field. It is the ultimative basis of successful companies that breed crop plants for seed production. Seed quality is a complex trait that is determined by interactions between multiple genetic factors and environmental conditions. Modern approches to improve seed quality therefore combine classical genetics, plant molecular biology and a variety of seed technologies. These "seed biotechnologies" enhance physiological quality, vigor and synchronity to establish a crop in the field under diverse environmental conditions. 

The methods to improve seed quality by mechanical techniques include polishing off or rubbing off seed coat (testa) or fruit coat (pericarp) projections or hairs (abgeriebenes Saatgut), sorting into defined seed size classes or sorting by seed density. Examples: seeds of horticultural species. Sugar beet fruits, where polishing removes projections of the pericarp/perianth, which is followed by sorting into defined seed size classes.

SUBJECT MATTER

Seed technologies (seed enhancements, seed treatments) include priming, pelleting, coating, artificial seeds, and other novel seed treatment methods of applied seed biology. Our basic and applied seed research projects focus on embryo growth and on the different seed covering layers (e.g. testa, endosperm, pericarp), which are determinants of seed quality and exhibit the biodiversity of seed structures. Seed germination is controlled by environmental factors (light, temperature, water) and on plant hormones as endogenous regulators (gibberellins, abscisic acid, ethylene, auxin, cytokinins, brassinosteroids). The utilization of plant hormones and inhibitors of their biosynthesis and action in seed treatment technologies affects seed germination and seedling emergence. The genes, enzymes, signaling components and down-stream targets of plant hormones provide molecular marker for seed quality and seedling performance.

Important methods to enhance seed and seedling performance are through addition of chemicals to protect the seed from pathogens and/or to improve germination. Different techniques of  seed coating (Saatgutbeschichtung) and seed pelleting (Pillierung) are used for this.  Film-coating methods allow the chemicals to be applied in a synthetic polymer that is sprayed onto the seeds and provide a solid, thin coat covering them. The advantage of the polymers is that they adhere tightly to the seed and prevent loss of active materials like fungicides, nutrients, colorants or plant hormones. Some novel applications of film coating are used to modify imbibition and germination. They can confer temperature-sensitive water permeability to seeds or affect gaseous exchange.  They control the timing of seed germination and seedling emergence. Certain temperature-dependent water-resistant polymers can delay imbibition until the climatic conditions become suitable for continued seedling growth.

Seed pelleting adds thicker artificial coverings to seeds, which can be used to cover irregular seed shapes and add chemicals to the pellet matrix, e.g. of sugar beet or vegetable seeds. The pellet matrix consists of filling materials and glue. Loam, starch, tyllose (cellulose derivative) or polyacrylate/polyacrylamide polymers are commercially used. A film coat can be added onto the pelleting layer as shown in the figure above. Seed pelleting is also used to increase the size of very small horticultural seeds. This provides improved planting features, e.g. singulate planting, the use of planting machines, or precise placement and visibility in/on the soil. The images below this text are examples for pelleting of very small horticultural seeds.

Seed priming is the most important physiological seed enhancement method. Seed priming is an hydration treatment that allows controlled imbibition and induction of the pregerminative metabolism ("activation"), but radicle emergence is prevented. The hydration treatment stopped before dessication tolerance lost. An important problem stop the priming process in the right moment, this time depends on the species and the seed batch. Molecular marker can be used to control the priming process. Priming solutions can be supplemented with plant hormones or beneficial microorganisms. The seeds can be dried back for storage, distribution and planting. Germination speed and synchronity of primed seeds are enhanced (see figures below) and can be interpreted in the way that priming increases seed vigor (short or no "activation" time). A wider temperature range for germination, release of dormancy and faster emergence of uniform seedlings is achieved. This leads to better crop stands and higher yields. A practical drawback of primed seeds is often a decrease in storability and the need for cool storage temperatures.

Several types of seed priming are commonly used:

ü Osmopriming (osmoconditioning) is the standard priming technique. Seeds are incubated in well aerated solutions with a low water potential, and afterwards washes and dried. The low water potential of the solutions can be achieved by adding osmotica like mannitol, polyethyleneglycol (PEG) or salts like KCl.

ü Hydropriming (drum priming) is achieved by continuous or successive addition of a limited amount of water to the seeds. A drum is used for this purpose and the water can also be applied by humid air. 'On-farm steeping' is the cheep and useful technique that is practized by incubating seeds (cereals, legumes) for a limited time in warm water.

ü Matrixpriming (matriconditioning) is the incubation of seeds in a solid, insoluble matrix (vermiculite, diatomaceous earth, cross-linked highly water-absorbent polymers) with a limited amount of water. This method confers a slow imbibition.

ü Pregerminated seeds is only possible with a few species. In contrast to normal priming, seeds are allowed to perform radicle protrusion. This is followed by sorting for specific stages, a treatment that reinduces dessication tolerance, and drying. The use of pregerminated seeds causes rapid and uniform seedling development.

One major seed problem in the Tropics is the lack of definitive information on the phenology of flowering and maturation of fruits and seeds. Unlike most temperate zone species, many tropical trees flower over a period of many months, so that multiple stages of seed maturity may be present at any one time on the same tree. This condition complicates seed collection, for there is no single definable period of seed maturation within a species or even among trees of the same species.

Other collection problems are presented by the spatial distribution or size of trees in natural stands. In moist tropical forests, fruit-bearing limbs of desirable trees may be as much as 35 meters above the forest floor. Unless seeds can be collected from the ground after natural seedfall, climbing is the only practical option.

Predators present another major problem in the Tropics. Animals are natural seed dispersal mechanisms in tropical ecosystems, but they complicate things for human seed collectors. And when seeds are dispersed on the ground, numerous birds, rodents, and insects are there to eat them. Timely collections are needed to avoid these losses, but incomplete knowledge about fruiting phenology and wide spatial distribution of trees combine to make this difficult.

In contrast to the common image of rapid germination in tropical forests, there are many species that exhibit seed dormancy. While many species germinate promptly when dispersed, others exhibit long delays in germination. Seed dormancy is most common among leguminous species and species of dry tropical forests. Seed coat dormancy, the most common cause, is easily overcome with scarification, but other, more complex dormancies may be encountered.

Dormancy of crop and horticultural seeds is an unwanted trait for horticulture. However, a certain degree of dormancy is required to prevent viviparous germination on the plant, e.g. preharvest sprouting of cereal crops. Dormancy is the failure of fully developed, mature, viable seed to germinate even under favorable physical conditions (like moisture and temperature). The seed with dormancy is termed as dormant seed.

The most challenging problem for seed science in the Tropics is storage of recalcitrant seeds. The intolerance of tropical recalcitrant seeds to both low moisture content and low temperature prevents the use of these conditions for storage. Temperate recalcitrant seeds fare better in storage because low temperatures can be used, but both groups have short storage lives. Solution of the storage problem for one of the recalcitrant seed groups should benefit the other group as well.

CONCLUSION

·       Supply high quality seeds, means seeds of high yielding varieties, varieties with resistance to diseases and pests.

·       To increase agricultural production by supply of quality seed.

·       To assure rapid seed multiplication of desirable varieties.

·       Timely supply of seeds, i.e. well before the sowing season.

·       Supply of seeds at reasonable prices.

Some principles are considered during production and seed multiplication. Those are given on the page Principles of seed production.

There are plenty of challenges in seed technology of tropical species, and all of them can be done without massive expenditures for laboratories and equipment. Most of the research suggested in this article must be done on-site in the Tropics, not in the comfort of well-equipped temperate-zone laboratories. There are many competent seed researchers and institutions in tropical regions around the world. This is not a complete list, by any means, and new programs seem to be continually coming on line. While seed research is not the primary focus of some of these institutions, they all have the capability to solve their respective problems.

Research papers on tropical tree seeds appear now in scientific journals at an ever increasing rate, which is evidence of two trends. One is that many more researchers from the temperate zone are working on tropical seed problems these days, and the second is that the capabilities of research staffs and institutions in tropical countries are increasing. In the long run, it will be the scientists from the tropical countries who contribute the most to meeting the challenges of tree seed technology in tropical forestry.

BIBLIOGRAPHY

Bonner, F.T. 1992. Seed Technology: A Challenge for Tropical Forestry. Tree Planters' Notes 43(4):142-145. Project leader, USDA Forest Service Southern Forest Experiment Station, Starkville, Mississippi.

Efields Media. 2010. Seed Technology. http://theagricos.com/seed-technology/

Leubner, Gerhard. 2000. The Seed Biology Place. http://www.seedbiology.de/seedtechnology.asp