How many meiotic divisions are required for the formation of 200 seeds of Capsella?
1 Answer
250 meiotic divisions are required for the formation of 200 seeds of Capsella.
Explanation:
The seed is a ripened ovule ( megasporangium ). In young megasporangium , only one cell functions as megaspore mother cell that undergoes meiosis to form 4 haploid cells. Out of these only one cell is functional and develops into megaspore.
Megaspore develops into female gametophyte( embryo sac ), that is retained permanently in the megasporangium (ovule) as it is indehiscent. One of the cells of embryo-sac functions as oosphere or egg.
Thus, one meiotic division is required for the formation of one ooshere (female gamete or egg).
Pollen grains (microspores) are produced in the anther. The anther has 4 lobes, each representing a micro-sporangium . Cells of sporogenous tissue in micro-sporangium function as microspore mother cells. Each microspore mother cell undergoes meiosis to form 4 haploid micropores. Each microspore (pollen grain ) develops into male gametophyte that produces male gamete.
Thus one meiotic division produces 4 micropores and consequently 4 male gametes.
The oosphere is fertilized by male gamete to form diploid oospore that develops into embryo. The later is enclosed permanently inside ovule, that ripens into seed.
Four oospheres and four male gametes are required for the formation of four seeds. Four meiotic divisions are required for the formation of four oospheres and only one meiotic division for the formation of four male gametes.
Thus 5 meiotic divisions are needed for the formation of 4 seeds and 250 meiotic divisions are required fro the formation of 200 seeds.
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