This document provides an overview of seed germination in pulses. It discusses the key requirements for germination including water, oxygen, carbon dioxide, temperature, and light. It describes the two main types of seed germination - epigeal and hypogeal. The document also outlines the main physiological and biochemical changes that occur during seed germination, including imbibition, respiration, enzyme activation, storage compound breakdown, and seedling emergence. Finally, it summarizes several studies that evaluated changes in enzyme activity and biochemical components in specific pulse crops like mung bean, cowpea, and chickpea during germination.
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
Germination is defined as the emergence of the radical
through the seed coat.
Germination 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,
A. Epigeal germination
B. Hypogeal germination
(A)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.
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. O2 & CO2
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 300 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-
1. Light intensity ( Lux or candlepower)
2. Light quality ( color or wavelength)
3. Day length
13. Physiological and biochemical changes
during seed germination
A. Imbibition
B. Respiration
C. Enzyme Activation
D. Initiation of embryo growth
E. Rapture of the seed coat
F. Emergence of the seedling
14.
15. 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-
1. Composition of the seed
2. Seed coat permeability
3. Water availability
16. CHIEF EVENTS OCCURE DURING
IMBIBITION
1. Absorption of water
2. Absorption of other substance
3. Release of gases
4. Increase in volume of seed due to swelling
5. Leakage of solute
17. 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.
18. 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.
20. 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
21. 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.
22. 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.
23. 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.
24. 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.
25. 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.
26. 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.
27. 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.
29. 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 co2 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.
30. 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.
acides
fatty
Glycerol
des
Triglyceri lipase
31. 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)
32. Protein Metabolism processes
After free amino acids are released from their
complexes, they may be further broken down by any of
three processes:-
1. Deamination to give ammonia and a carbon skeleton
that subsequently enter various metabolic processes.
2. Transamination enzyme to yield ketoacids which enter
the Krebs cycle for further breakdown to CO2, H2O
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.
34. 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.
35. 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.
36. 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.
37. 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.
38.
39. 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
40.
41. 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.
42.
43.
44. 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.
45. 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 .
46. 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
47. 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
48. .
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
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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
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