Tag: reproduction in higher plants

Endosperm is the nutritive tissue for the developing embryo and the seedlings. In angiosperm, the endosperm develops from triploid primary endosperm nucleus which is formed as a result of vegetative fertilization, triple fusion or fusion of male gamete with the secondary nucleus of the central cell. Generally, endosperm divides before zygote because it will provide nourishment to the developing zygote.

For the formation of male gametophyte, 1 meiosis and 2 mitoses are required.

After fertilization, the ovule matures into seeds and ovary into fruits. The process of fertilization is unique in angiosperms because it involves syngamy between male and female gametes and triple fusion between a male gamete and a secondary nucleus. Because two fertilization events are involved, it is called as double fertilization. The second fertilization is a fusion between three haploid nucleus (two forming a diploid secondary nucleus and one haploid male nucleus). Hence the secondary fertilization event is called as Triple fusion. It gives rise to a triploid primary endosperm nucleus (PEN). PEN later on gives rise to triploid endosperm. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen and the outer forms the testa. The seed coats of some monocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp.

Aleurone layer in the seed helps in embryo protection, utilization of stored food and storage of food. Aleurone is a protein found in protein granules of maturing seeds and tubers. The term also describes one of the two major cell types of the endosperm, the aleurone layer. The aleurone layer is the outermost layer of the endosperm, followed by the inner starchy endosperm. This layer of cells is sometimes referred to as the peripheral endosperm. It lies between the pericarp and the hyaline layer of the endosperm. Unlike the cells of the starchy endosperm, aleurone cells remain alive at maturity.
Thus, the correct answer is option D.

In hypogeal germination, epicotyl elongates and cotyledons remain underground. 
In epigeal germination, hypocotyl elongates and pushes cotyledons above the ground. 
Assertion is wrong because gram, pea and mango shows hypogeal germination.
Reason is true but it is not the right explanation for given assertion.
Thus, the correct answer is option C.

Orthodox seeds are seeds which will survive drying or freezing during ex-situ conservation. There is variation in the ability of orthodox seeds to withstand drying and storage with some seeds being more sensitive than others. Thus, some seeds are considered intermediate in their storage capability while others are fully orthodox.
Thus, the correct answer is option B.

The outer thick layer is called as testa and inner thin one as tegmen. The seed develops from the tissue, that is the integument which originally surrounds the ovule. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen and the outer forms the testa. The seed coats of some mononocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp.
Therefore, the correct answer is option C.