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.
Short Answer TypeDescribe any two devices in a flowering plant which prevent both autogamy and geitonogamy.
Autogamy: Transfer of pollen grains from the anther to the stigma of the same flower.
Geitonogamy: Transfer of pollen grains from the anther to the stigma of another flower of the same plant.
Two devices that prevent both autogamy and geitonogamy are:
(i) Self – incompatibility: This is a genetic mechanism & prevents self-pollen from fertilising the ovules by inhibiting pollen germination or pollen tube growth in the pistil.
(ii) Dioecious plants: Male and female flowers are present on different plants, that is each plant is either male or female.
Explain 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
Switch
