Seed dormancy and seed germination
Having detailed knowledge about seed dormancy and seed germination can helps us to know physiology of plants and helps us to increase our production.
|Seed dormancy and seed germination|
Types Of Seed Dormancy
Seed dormancy is classified on the basis of what actually causes the dormancy.
There are 3 types of seed dormancy which are:-
2.Innate dormancy:- Innate means within. Some growth inhibitors within the seed arrest its growth even in favourable condition.
Causes Of Seed Dormancy
1.Outer seed coat
a.Impermeable seed coat:- Due to impermeable seed coat water and O2 cannot enter the seed and fails to germinate and goes under dormant phase.
In this, even if seed imbibes water, embryo cannot expand to fixed seed coat and all metabolic activities stops and seed automatically goes under dormant phase.
c.Chemical growth inhibitors:-
Other Causes Of Dormancy
a.phisiologically shallow dormancy:- present in some freshly harvested seed. Disappears with dry storage over a period of days or months.
c.Temperature dormancy:-Many seeds are specific in their temperature requirements. Some need alternating temperatures.
Others germinate over a narrow range of temperatures and go dormant above or below this range.
a. Physical(Outer part) dormancy
It is a type of dormancy in seed which occurs due to impermeable seed coat. If a seed has hard seed coat then water and O2 cannot enters into seed due to which seed cannot germinate and goes into dormant phase.
~Mechanical dormancy is similar to physical dormancy i.e it is also due to outer hard coverings. But in this dormancy, embryo becomes unable to expand due to which seed cannot germinate and goes into dormant phase.
c.chemical inhibitors dormancy
~Different types of growth inhibitors are present within the seed and on seed coat which suppresses growth of seedling and seeds becomes dormant.
Internal Factors Causing Seed Dormancy
a. Physiological dormancy/Dormancy due to chemical changes.
~In this type of dormancy, seed is unable to germinate into new seedling because there is no any physiological or chemical changes inside the seed.
For seed to germinate there must be chemical changes. For example:-increase in GA3 causes amylase production which hydrolyses carbohydrate and provides nutrition for germination.
b.Morphological dormancy/Dormancy due to undeveloped embryo
For seed to germinate, embryo must be mature enough. This is because, embryo undergoes division and gives rise to radical and plumule which is th intial step of germination.
Sometimes, embryo inside seed doesn’t mature enough due to different condition and causes seed dormancy. Some seeds embryo goes on maturing even after harvesting. So sowing seed without storage for some period can cause morphological dormancy.
Sometimes both internal and external factors acts on seed and causes dormancy which is called combined dormancy.
Breaking Of Seed Dormancy
Seed dormancy has much more negative effects on production of certain crops. so, seed dormancy should be break in order to get lot of production.
It can be done by rubbing with sandpaper or with knife. Sometimes acid and hot water can also be used to make scarification.
Seed which are scarfied grows much faster than normal seed. Try it on bitter gourd for excellent results and comparision.
Stratification means giving cold or chilling treatment to the seeds before sowing. Some seeds needs chilling treatment otherwise they do not germinate.
For example, apple seed should be stored in (1-5)०c for their good germination.
~By vigorously shaking seeds.
~ pressure treatement etc…
Importance Of Seed Dormancy
Now that, we have learned about seed dormancy, it is necessary to know about its importance.
Hope you guys gets the answer you want. Thank you for reading this article with this much attention.
So, read the article till end to have complete package of knowledge.
Seed germination basically means the growth of seed. Growth into what??- Growth into seedling.If we explained it on more scientific way, the definition on seed germination is given below:-
If we didn’t give special attention at this phase, we might get huge loss in production of crops.
1.Imbibation of water
This is the first step of seed germination. After the seed is sown to soil, it absorbs water from soil. After adsorbing water, the seed swells up. Then O2 also enters into seed.
2.Activation of enzymes
As soon as the seed imbibes water, different enzymes such as amylase gets activated. These enzymes starts to act on stored food materials.
3.Breakdown of complex food materials
Enzymes acts upon complex food materials and converts them into simpler form such as glucose. Embryo uses these energy and start to divide and forms different many cells
4.Formation of radicle and plumule
After the use of energy and division of embryo, new structures of radicle and plumule forms and they moves towards seed coat.
5.Rupture of seed coat and emergence of radicle and plumule
Finally, outer seed coat ruptures and plumule emerges out of seed coat which later forms shoot system. Similarly, Radicle also emerges out of seed coat towards downward which later develops into root system.
6.Emergence of seedling
At last seedling emerges and new plant is formed.
Types Of Seed Germination
Germination of seed is classified into two types based on movement of cotyledon below or above the soil.
Epi means above, so in this type of germination cotyledons rise above the soil surface.
|Epigeal germination of seed|
Most of the dicots have epigeal germination(@ed)
Hypo means below, so in this type of germination cotyledons remains below soil surface.
|Hypogeal germination of seed|
All monocots and few dicots have hypogeal germination.
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