a) draw a longitudinal section of a pistil of an angiosperm showing the growth of the pollen tube up to the micropyle of the ovule. Label (i) stigma (ii) embryo sac (iii) pollen tube (iv) micropyle. (b) explain the events that occur up to fertilization, when the compatible pollen grain lands on the stigma.
Answers
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The pollen tube initially penetrates and grows through the intercellular spaces of the stigma and then grows through the transmitting tract to the placenta connected to an ovule. The pollen tube grows along the surface of the ovule's funiculus, through the micropyle, and into the female gametophyte.The pollen tube grows from the pollen grain to the micropyle. ... The tip of the growing pollen tube releases digestive enzymes into the style. Suggest the role of these digestive enzymes in the growth of the pollen tube.The pollen tube arrives in the micropyle of the integument of the ovule, and enters the embryo sac. The synergids of the embryo sac literally put their energies together to burst the end of the pollen tube. ... The two sperm cells exit the pollen tube through the burst end. One sperm cell unites with the egg.1)Some pollen grains fail to germinate as they don't get all the essential conditions for the germination of pollen. 2)No, pollen grains of other species do not grow. ... It is so because older germinated pollens will have longer developed tube as compare to newly germinated pollen which will have shorter pollen tube.Once a pollen grain settles on a compatible pistil, it may germinate in response to a sugary fluid secreted by the mature stigma. Lipids at the surface of the stigma may also stimulate pollen tube growth for compatible pollen.Within 2 to 3 minutes, the pollen left on stigma starts to germinate, to grow pollen tube toward the egg cell. Pollen tubes are the pathways for sperm to reach the egg. The pollen tube reaches the ovule. It happens within 15-60 minuts after the pollen.
noun Botany.
noun Botany.the megaspore of a seed-bearing plant, situated within the ovule, giving rise to the endosperm and forming the egg cell or nucleus from which the embryo plant develops after fertilization.A pollen grain on the stigma grows a tiny tube, all the way down the style to the ovary. This pollen tube carries a male gamete to meet a female gamete in an ovule. ... The fertilised ovule goes on to form a seed, which contains a food store and an embryo that will later grow into a new plant
