Pollen grains are able to withstand extremes of temperature and dessication because their exine is composed of
The pollen tube usually enters the embryo sac
(1) through one of the synergids
(2) by directly penetrating the egg
(3) between one synergid and central cell
(4) by knocking off the antipodal cells
Double fertilization involves
(1) fertilization of the egg by two male gametes
(2) fertilization of two eggs in the same embryo sac by two sperms brought by one pollen tube
(3) fertilization of the egg and the central cell by two sperms brought by different pollen tubes
(4) fertilization of the egg and the central cell by two sperms brought by the same pollen tube.
Plants of which one of the following groups of genera are pollinated by the same agency?
(1) Triticum, Cocos, Mangifera
(2) Ficus, Kigelia, Casuarina
(3) Salvia, Morus, Euphorbia
(4) Bombax, Butea, Bauhinia
(1) formation of seeds by fusion of gametes
(2) formation of seed without syngamy and meiosis
(3) formation of seeds with syngamy but no meiosis
(4) none of the above
Even after killing the generative cell with a laser beam, the pollen grain of a flowering plant germinates and produces normal pollen tube because
(1) laser beam stimulates pollen germination and pollen tube growth
(2) the laser beam does not damage the region from which pollen tube emerges
(3) the contents of killed generative cell permits germination and pollen tube growth
(4) the vegetative cell has not been damaged.
What is the charasteristic of tapetum ?
(1) It does not store food.
(2) It is multi-nucleated.
(3) It is multi-layered structure.
(4) It nourishes the megaspore.
Cleistogamy is leadingover anthesis because
(1) pollination agent is not required
(2) it assures heterozygosity
(3) it favours insect pollination
(4) it allows xenogamy
Sporopollenin is a constituent of pollen exine.
It can be degraded by the action of
(2) high temperature
(3) strong acids
(4) cannot be degraded
The pollen grains of rice and wheat lose their viability in ___ minutes of their release.