Short Answer TypeA pollen grain in angiosperm at the time of dehiscence from an anther could be 2-celled or 3-celled. Explain. How are the cells placed within the pollen grain when shed at a 2-celled stage ?
(a) Can a plant flowering in Mumbai be pollinated by pollen grains of the same species growing in New Delhi ? Provide explanations to your answer.
Long Answer Type(a) When a seed of an orange is squeezed, many embryos, instead of one are observed. Explain how it is possible.
(b) Are these embryos genetically similar or different ? Comment.
(a) It is due to polyembryony. Occurrence of more than one embryos in a seed is called as POLYEMBRYONY. In orange, the nucellar cells, synergid or integument cells develops into a number of embryos of different sizes. eg : - Citrus.
* Sometimes formation of more than one egg in an embryo sac can lead to polyembryony.
(b) In such embryos parental characters are maintained hence they are genetically similar. In this process, there is no segregation of characters in the offspring (progeny).
Short Answer TypeExplain the events up to double fertilisation after the pollen tube enters one of the synergids in an ovule of an angiosperm.
Multiple Choice QuestionsWhich one of the following statements is not true?
Exine of pollen grains is made up of sporopollenin
Pollen grains of many species cause severe allergies
Stored pollen in liquid nitrogen can be used in the crop breeding programmes
Stored pollen in liquid nitrogen can be used in the crop breeding programmes
In bryophytes and pteridophytes, transport of male gametes requires
insects
birds
water
water
Proximal end of the filament of stamen is attached to the
connective
placenta
thalamus
thalamus
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