Types of seed and seed dormancy

Seed

1. TYPES OF SEED AND SEED DORMANCY NAME: SHAHID JAMAL NEPTUNE CODE: GDWKUX COURSE: M.Sc AGRICULTURAL BIOTECHNOLOGY

2. HIGHLIGHTS TO BE COVERED DURING MY PRSENTATION WHAT IS SEED ? SEED STRUCTURE TYPES OF SEED SEED DORMANCY

3. WHAT IS SEED? In broad sense Seed is a material which is used for planting or regeneration purpose. Scientifically Seed is a fertilized matured ovule together covered with seed coat is called seed. Technological point of view Seed is a fertilized ripened ovule consisting of three main parts namely seed coat, endosperm and embryo, which in due course gives rise to a new plant

4. SEED STRUCTURE External • Seed coat ( testa )

5. • Hilum

6. Embryo • Cotyledon • Epicotyl / Hypocotyl • Plumule • Radical

7. TYPES OF SEED Seed are classified mainly on the basis of the number of the cotyledons presents: Dicotyledonous seed Monocotyledonous seed Dicot seed example: Mango, Gram, Pea Monocot seed example: Wheat, Bajra, Maize, Rice https://quizlet.com/339944422/reproduction-seeds-and-flowers-study-guide-flash-cards/

8. On the basis of the second criteria the seeds are classified as a presence or absence of the endosperm 1. Endospermic or Albuminous seeds 2. Non-endospermic or Exalbuminous seeds Endosperm living: Ricinus communis Endosperm dead: cereals Examples: onion, Ricinus, cereals, tobacco, maize e.g. pea, bean, apple, sunflower, Arabidopsis, squash

9. SEED DORMANCY Seed dormancy is defined as a state in which seeds are prevented from germinating even under environmental conditions normally favourable for germination. These conditions are a complex combination of water, light, temperature, gasses, mechanical restrictions, seed coats, and hormone structures According to Amen (1963) dormancy is defined as "endogenously controlled but environmentally imposed and it is the temporarily suspension of growth accompanied by reduced metabolic activity and relatively independent of ambient environmental conditions.” According to Simpson (1965) seed dormancy is defined as failure of viable seed to germinate at specified length of time in a set of environmental conditions, later evoke germination when the restrictive state of seed is removed naturally or artificially.

10. Based on Amen (1963) definition, the dormancy can be classified into two category: A. Innate dormancy / Primary dormancy B. Secondary dormancy A. Innate dormancy / primary dormancy It is the state of dormancy in which the dormancy induced in the seeds at the time of dispersal from the mother plant i.e. the dormancy may be during the maturity and after the maturity but before seed is dispersed from mother plant.

11. B. Secondary dormancy Secondary dormancy is defined as it can take place only in a matured and imbibed seed by certain environmental conditions, which are unfavourable to germination. (e.g.) Spring wheat variety and winter barley variety.’ Primary dormancy is further classified into endogenous and exogenous . Exogenous dormancy is due to seed coat factor either due to presence of inhibitors or the hard seed nature. It is further classified into, Physical – Dormancy is due to hard seed coat which prevents the entry of water and sometimes gaseous exchange is also blocked. e.g. Hard seeds of pulses, Prosopis, sapota etc., Chemical – Presence of some inhibitors in seeds coat which stopped the germination

12. Mechanical – restriction of the growth of protruding radicle due to the structure. (e.g.) inadequate space in the seeds of Terminalia sp . Endogenous dormancy – Dormancy due to the embryo. May be the presence of inhibitors , immature embryo or combination of the both. It is further classified into Morphological – Due to immature embryo, which is not able to put forth germination even under the favourable conditions . (e.g.) Apple Physiological – Due to arrest of the metabolic activities in the seeds due to presence of some inhibitors like ABA( Absicis Acid), coumarines , phenols etc., e.g. cereals, sunflower, lettuce – most common Morphophysiological – Combination of immature embryo with the inhibitors. e.g. Fraxinus excelsior

13. Secondary Dormancy Whose germination is constrained , fail to recover even when the inhibitory factor is eliminated. Adoptive mechanism to pass the adverse environmental condition. Types of secondary dormancy Thermo –Dormancy due to the temperature Skoto – Light; Photo – Quality of light and Osmotic – stress or high osmotic stress that prevents the germination

14. REFERENCES https://www.kean.edu/~fosborne/resources/ex6d.htm http://lugezi.com/images/ http://agritech.tnau.ac.in/seed_certification/seed%20tech%20agri%20index/seedconcepts.html https://byjus.com/biology/seed-dormancy/ http://www.seedbiology.de/structure.asp#structure1 https://www.toppr.com/guides/biology/morphology-of-flowering-plants/the-seed/