seed germination pulsee.pptx

Physical and chemical changes during seed germination

1. WEL COME WELCOME

2. PHYSIOLOGY AND BIOCHEMISTRY OF SEED GERMINATION IN PULSES Presented By, KALE TANHAJI SHIVAJI Ph.D Scholar Department of Vegetable Science, Dr. P. D. K. V ., Akola

3. Germination of Seeds G ermination is defined as the emergence of the radical through the seed coat. G ermination to be the resumption of active growth by the embryo resulting in the rupture of the seed coat and emergence of a young plant.

4. Types of Seed Germination Based on the fate of the cotyledons or storage organs: - Seed germination is two types, Epigeal germination Hypogeal germination EPIGEAL GERMINATION :- During germination the cotyledons are raised above the ground where they continue to provide nutritive support to the growing point. Example:- Bean, Mung bean, Urd bean

5. (B) HYPOGEAL GERMINATION :- During germination the cotyledons remain beneath the soil while the plumule pushes upward and emerge above the ground. Example:- Pea , Chickpea, Tur.

6. Requirements for Germination 1-Water 2- 0 2 & CO 2 3-Temperature 4-Light

7. Water:- water is a basic requirement for germination. It is essential for enzyme activation, breakdown, translocation , and use of reserve storage material. Field capacity moisture is about optimum for germination in soil. The initial stages of germination may even proceed with moisture available from a high-humidity environment, although such conditions are not adequate for complete germination. This is often demonstrated by a phenomenon known as precocious germination or sprouting when seeds actually germinate in the head or pod following rains or high-humidity conditions. WATER

8. High moisture levels may inhibit germination. For example, when moisture content was increased from 20% to 40% , dwarf bean germination was reported to decrease significantly (Ensor 1967). Critical moisture content concept Tur – 35% Pea – 45% Bean – 25% Chickpea – 40% Cont…

9. O 2 & CO 2 Air is composed of about 20% oxygen, 0.03% carbon dioxide and 80% nitrogen gas. Carbon dioxide concentrations higher than 0.03% retard germination, while nitrogen gas has no influence. Respiration increase sharply during seed germination. Since respiration is essentially an oxidative process, an adequate supply of oxygen must be available. If the oxygen concentration is reduced substantantially below that of air, germination most of the seeds is retarded.

10. TEMPERATURE The effect on germination can be expressed in terms of cardinal temperature, that is minimum, optimum, and maximum temperatures at which germination occur. The minimum temperature is sometimes difficult to define since germination may actually be proceeding but at such a slow rate that determination of germination is often made before actual germination is completed. The optimum temperature may be defined as the temperature giving the greatest percentage of germination within the shortest time.

11. Cont… The maximum temperature is governed by the temperature at which denaturation of proteins essential for germination occurs. As a general rule, temperate-region seeds require lower temperature than do tropical-region seeds Wild species have lower temperature requirements than do domesticated plants. High-quality seeds are able to germinate under wider temperature ranges than low-quality seeds. The optimum temperature for most of seeds is between 15 and 30 C.

12. LIGHT The influence of light on germination of seeds has long been recognized. The mechanism of light control in seed germination is similar to that controlling floral induction, stem elongation, pigment formation in certain fruits and leaves, radicle development of certain seedling, and unfolding of the epicotyl of bean seedling. Three types of light effect the germination- Light intensity ( Lux or candlepower) Light quality ( color or wavelength) Day length

13. Physiological and biochemical changes during seed germination Imbibition Respiration Enzyme Activation Initiation of embryo growth Rapture of the seed coat Emergence of the seedling

14. IMBIBITION The early stages of imbibition or water uptake into a dry seed represent a crucial period for seed germination. It is the first key event that moves the seed from a dry, quiescent, dormant organism to the resumption of embryo growth. the extent to which water imbibition occurs is dependent on three factors- Composition of the seed Seed coat permeability Water availability

15. CHIEF EVENTS OCCURE DURING IMBIBITION Absorption of water 2. Absorption of other substance 3. Release of gases 4. Increase in volume of seed due to swelling 5. Leakage of solut e

16. B. Respiration :- Respiration involves the oxidative breakdown of certain organic seed constituents mainly sugars, starch, fatty acids and lipids. Rapid increase in respiration rate of embryo occurs. Sucrose is probably the respiratory substrate at this stage which is provided by endosperm.

17. C. Enzyme activation A triphasic pattern of water uptake has been demonstrated during the germination of most of seeds. Enzyme activation begins during phase I and II of imbibitions. During phase II, the seed undergoes many processes essential for germination. Increased respiration and leakage of nutrients from the imbibed seed lead to loss of dry weight. Finally, in phase III root elongation is observed. The root becomes functional during this phase and is responsible for the increased water uptake noted in phase III.

18. Stages of Germination

19. Water uptake By imbibitions = a physical process in seeds with a permeable seed coat Occurs whether seed is alive, dead, dormant or non-dormant. First 1 - 15 hrs = rapid uptake Followed by 15 - 50 hours of slow uptake Seeds generally do not wet uniformly Volume of seed increases Phase-I

20. Phase-II The process of enzyme activation during phase II of water imbibitions serves to break down stored tissue, aid in the transfer of nutrients from storage areas in the cotyledons or endosperm to the growing points, and chemical reactions that use breakdown products for the synthesis of new materials.

21. Phase-III Radicle emergence Result of cell enlargement Food reserves continue to be used. Enzymes degrade certain cell walls to permit exit of the radicle . GA promotes enzymatic cell wall hydrolysis and radicle emergence. ABA inhibits enzymatic cell wall hydrolysis.

22. Trigger Chemical Reaction During the enzyme activation phase include the synthesis of storage product enzyme such as alfa- amylase, ribonuclease and phosphatase. These events are mediated by the hormone gibberellic acid. However, during this lag phase many endoplasmic reticulum, ribosomes, and ribosomal RNA essential components of the enzyme synthesize. Such enzyme as ATPase , phytase, protease, lipase, and peroxidase all increase during enzyme activation.

23. Breakdown of storage tissues Generally, enzymes that break down carbohydrates, lipids, proteins, and phosphorous containing compounds are the first to be activated during phase II of water uptake by seeds. Since the embryonic axis requires energy for growth, storage compound must be hydrolyzed to soluble forms, translocated from cotyledon to the embryo, and transformed to energy molecules that can be immediately utilized by the embryonic axis.

24. Breakdown of storage tissues In dicots pulses, the hormonal regulation of storage product degradation is not as clear as in monocots. This may be due to the absence of an aleurone-like tissue that synthesizes hydrolytic enzymes. In some instance, gibberellins are known to trigger hydrolytic enzyme synthesis, but the degree of activation is never as great as that noted in cereals.

25. Breakdown of storage tissues Some investigation believe that dicot seed germination is mediated by the growing embryonic axis. As the axis continues to grow, it concentration of compounds in the cotyledons, which in turn stimulates the hydrolysis of other storage reserves for use by the embryonic axis. Should this stimulation prove to be too great, and hydrolyzed storage products begin to accumulate, a feedback mechanism may be operative that retards further storage reserve hydrolysis.

26. Carbohydrate Metabolism Amylopectin and amylase are hydrolyzed by alfa - and β-amylase enzymes. These enzyme split either starch structure yielding the diasaccharide maltose, which is then split into two monosaccharide glucose units. Some glucose units are converted into the highly mobile diasaccharide sucrose for translocation to other sites, after which it is reconverted to glucose or used directly in synthesis.

27. Carbohydrate Metabolism steps

28. Carbohydrate Metabolism Glucose may be further broken down by respiration. The first step is known as glycolysis,which yields two pyruvic acid molecules. These than are completely broken down into co 2 and water by a series of reactions known as the tricarboxylic acid (Kreb) cycle. The reactions of glycolysis occur in the cytoplasm, while those of the kreb cycle occur in the mitochondria. Both processes yield energy as ATP.

29. Lipid Metabolism Plants store large amount of neutral lipids or fats as reserve food in their seeds. During germination, the fats are hydrolyzed into fatty acids and glycerol by lipase enzyme. Fatty acids are further converted into acetyl – CoA by the process, β - oxidation. The acetyl CoA is further converted into sucrose via glyoxylate cycle and is transported to the growing embryonic axis.  

30. Protein Metabolism Relatively little is known about the exact nature of reserve protein breakdown during seed germination. However, proteinases, the proteolytic enzymes (Enopeptidases,carboxypeptidases,aminopeptidases) (Bond and Bowles 1983) are involved in cleaving the peptide bonds of the protein and releasing the amino acids. Proteinases have been observed in many seeds and increase rapidly during germination.(Ryan 1973) proteolytic enzyme differ in their specificity in attacking certain peptide linkages. In soybeans, protein bodies are hydrolyzed by internal digestion (Wilson 1987)

31. Protein Metabolism processes After free amino acids are released from their complexes, they may be further broken down by any of three processes:- Deamination to give ammonia and a carbon skeleton that subsequently enter various metabolic processes. Transamination enzyme to yield ketoacids which enter the Krebs cycle for further breakdown to CO 2 , H 2 O and energy (ATP). Direct utilization for synthesis of new proteins in other parts of the germinating seed. Regardless of the pathway followed, the breakdown products are eventually available for use by the developing seed.

32. Phosphorus-containing Compound About 80% of the phosphorus in seed is stored as calcium, magnesium, or manganese salts of inositol hexaphosphate, or phytin. The other 20% is in organic compounds such as nucleotides, nucleic acid, phospholipids, phosphorylated sugars, phosphoproteins and a trace of inorganic phosphate. During seed germination, phytin is broken down, releasing inorganic phosphorus for synthesis of othe phosphorus-containing compounds. its breakdown is catalyzed by phytase, a phosphatase enzyme.

33. D. Initiation of Embryo Growth In Vigna sinensis (cowpea), the major storage tissues, the cotyledons, undergo a decreased in dry weight as the hypocotyl and subsequently the epicotyl, show increases. Soluble carbohydrates, soluble nitrogen, and nucleic acid phosphorus levels decrease in the cotyledons and are found in the emerging embryonic organs of the hypocotyls, roots, epicotyl, and plumule. http://www.rbgsyd.nsw.gov.au/

34. Emergence of the Radicle The actual emergence of the radicle, which signals that the germination process is complete, can be accomplished through either cell elongation or cell division.

35. Physiological and Biochemical Changes in major pulses during Germination  Evaluation of changes in phytase, α-amylase and protease activities of some legume seeds during germination. Ghavidel and Davoodi (2011) Evaluated Changes in Phytase, α-Amylase and Protease Activities of Some Legume Seeds during Germination in Mung bean (Phascolus aureus), cowpea (Vigna catjang), lentil (Lens culinaris) and chickpea (Cicer arietinum). Untreated, soaked and germinated (for 24, 48 and 72 h) legume seeds were analyzed for phytase, α-amylase and protease activities. Enzymes activities increased significantly on pre-germination soaking. Enzymatic activities of all legumes improved significantly and reached maximum during the course of germination up to 72 h. However, maximum protease activity in mung bean was at 48 h germination and declined thereafter. Germination as a biotechnological technique improved enzymatic activities in all legume seeds.

36. Changes of the enzymes activity during Germination of different mungbean varieties. Rahman (2007) Studied changes of the Enzymes Activity During Germination of Different Mungbean Varieties. The changes in the contents of enzymes activity of the seed of three varieties of mungbean were analysed at different hour of germination. Resulted Amylase and invertase activity were tremendously increased 200-220 % and 165-175 % respectively at 24 hour of germination and decreased gradually from 48-96 hour of germination. Protease activity was remarkably increased at 24 hour then further increased upto 48 hour (131-161%) and then decreased from 72-96 hour of germination. BARIMung-3 variety showed the best result i.e the highest amount of enzymes activity among the three varieties of mungbean at 24 hour of germinaton

37. Biochemical changes in cotyledons of germinating mung bean seeds from summer and rainy seasons . Vijaylaxmi (2013) Studied Biochemical changes during germination in mung bean [Vigna radiata (L.) Wilczek] seedlings during summer and rainy seasons. Activities of amylase and protease, concentrations of soluble sugars, soluble proteins, total nitrogen and free amino acids were studied at an interval of 12 h till 120 h. The results on the analysis of biochemical components showed that biochemical behavior of germinating seedlings varied in seed lots collected during summer and rainy seasons. Seeds collected from summer season had lower levels of germination percentage along with lower levels of activities for a-amylase, protease, soluble sugars, free amino acids and soluble proteins as compared to that from rainy season seeds.

38. Maneemegalai  and Nandakumar (2011) Germination causes alterations in the  chemical composition  of  Vigna radiata, Vigna mungo  and  Pennisetum typhoides . Carbohydrate content and energy value was decreased and protein and  ascorbic acid  content was increased during the process when compared to dry seeds. Germination did not alter the fat and ash content. Biochemical Studies on the Germinated Seeds of Vigna radiata (L.) R. Wilczek, Vigna mungo (L.) Hepper and Pennisetum typhoides (Burm f.) Stapf and C.E Hubb. 

39. Effect of Soaking Condition and Temperature on Imbibition Rate of Maize and Chickpea Seeds. Rahman et.al 2011 Imbibition for chickpea seed increased with increasing temperature and the rate of water absorption was always higher in anaerobic condition than the aerobic condition. The present study concludes that optimum duration of soaking for chickpea seeds at 31, 25 and 15°C of soaking temperature could be 6, 9 and 18 h, respectively .

40. CONCLUSION Various abiotic factors affects the germination Moisture, Temperature, Air, Light etc. Degradation reserve food material occurs carbohydrate, lipids, proteins, phytin etc. Activation of enzymes amylase, lipase, peroxidase, protease etc. Emregence of seedling

41. References . Beryln, G.P. 1972. Seed germination and morphogenesis. In: Seed Biology, ed . T.T. Kozlowski pp . 223-228. New York: Academic Press . Bond , H.M. and D.J. Bowles. 1983. Characterization of soybean endopeptidase activity using exogenous and endogenous substrates . Plant physiology 72:345-350. Ghavidel,. R A. and M.G Davoodi. 2011. Evaluation of changes in phytase, α-amylase and protease activities of some legume seeds during germination. International Conference on Bioscience, Biochemistry and Bioinformatics IPCBEE vol.5 Ensor , H.L. 1967. The influence of water content of sand on the germination of dwarf beans ( Phaseolus vulgaris L.). proceeding of the International Seed Testing Association 32(1):13-30 . Klein, S. 1955. Aspects of nitrogen metabolism in germinating lettuce seed with special emphasis on three amino acid (in Hebrew). Ph.D. dissertation, Hebrew University, Jerusalem Maneemegalai, S.,and S.Nandakumar, 2011.Biochemical Studies on the Germinated Seeds of Vigna radiata (L.) R. Wilczek, Vigna mungo (L.) Hepper and Pennisetum typhoides (Burm f.) Stapf and C.E Hubb. International Journal of Agricultural Research, 6: 601-606

42. . McDonald, M.B. 1994. Seed germination and seedling establishment. In: Physiology and Determination of Crop Yield, eds. K.J. Boote and T.R. Sinclair. Madison, Wisc., Crop science society of America. McDonald, M.B., C.W. Vertucci, and E.E. Roos. 1988. Seed coat regulation of soybean seed imbibition. Crop Science 28:987-992. McDonald, M.B., C.W. Vertucci, and E.E. Roos. 1988b.soybean seed imbibitions: water absorption by seed parts. Crop Science 28:993- 997. Rahman, M.M., L. d Banu, M. M Rahman and U. F Shahjadee. 2007. Changes of the enzymes activity during Germination of different mungbean varieties. Bangladesh J. Sci. Ind. Res. 42(2), 213-216, Rahman,M.M,. K. U Ahammad and M. M Alam, 2011. Effect of Soaking Condition and Temperature on Imbibition Rate of Maize and Chickpea Seeds. Research Journal of Seed Science, 4: 117-124 . Ryan, C.A. 1973. Proteolytic enzyme and their inhibitors. Annual Review of Plant Physiology 24:173-196. Vijaylaxmi 2013. Biochemical changes in cotyledons of germinating mung bean seeds from summer and rainy seasons. Ind J Plant Physiol. 18(4):377–380

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