Stages of seed development

Different stages involved in Seed development- Seed production tech

1. STAGES OF SEED DEVELOPMENT

2. POLLINATION & FERTILIZATION

3. SEED DEVELOPMENT The I ntegument of the ovule – seed coat Nucellus – absorbed and absent Endosperm Monocot : Max morphological development Dicot : Used up by the developing embryo.

4. EMBRYO DEVELOPMENT The first few cell division from the zygote forms the Pro-embryo . Although the mature embryo of monocotyledons and dicotyledons appears considerably different, their pattern of embryogeny are similar .

5. The Pro-embryo is divided into Suspensor and Embryo proper . The suspensor forms into a chain of cells, pushing the embryo proper into the center of the ovule thus making it in contact with the available food supply

6. ENDOSPERM DEVELOPMENT Endosperm formation starts prior to embryo formation. Reaches its maximum morphological development at physiological maturity .

7. There are 3 types of endosperm development nuclear - where the endosperm nucleus undergoes several divisions prior to cell wall formation, e.g., wheat apple, squash. (b) cellular - in which there is no free nuclear phase

8. (c) helobial - where the free nuclear division is preceded, and is followed by cellularization as in some monocots

9. SEED GROWTH & MATURATION The seed is said to have physiologically matured only when it attains maximum dry weight, germinability and vigour . Normally the seed is harvested at field maturity, a stage when the moisture content is reduced to about 6-10 % in wheat.

10. PHYSIOLOGICAL CHANGES Water uptake Respiration Mobilization of reserve materials BIOCHEMICAL CHANGES Nucleic acids Proteins Carbohydrates Inorganic nutrients

11. ENVIRONMENTAL FACTORS SOIL FERTILITY TEMPERATURE WATER LIGHT

12. MATURATION & DRYING Physiological maturity is identified as maximum seed dry matter accumulation Physiological maturity is reached when there is no further significant increase in seed dry weight

13. T he first concept of physiological maturity was proposed by Shaw and Loomis in 1950 as the stage in which the seed possesses maximum dry weight and yield . Physiological maturity has also been termed “ relative maturity ” by Aldrich in 1943, morphological maturity ” by Anderson in 1955 while others prefer to use terms such as “harvest maturity ”& “agronomic maturity ”

14. Probably the most accurate method of determining physiological maturity is the measurement of 14C assimilate uptake by the developing seed. This was demonstrated by TeKrony et al. (1979) Finally, the definition of physiological maturity based on seed maximum dry weight should be considered a reference point to characterize the end of seed development.