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42
While eating watermelons, all of us wish it was seedless. As a plant physiologist can you suggest any method by which this can be achieved.
Explanation
The process of parthenocarpy produce the seedless fruits. This is a process in which fruits are developed without fertilisation, so, seeds are not formed in the fruit. Artificially parthenocarpy can be induced by spraying auxin and gibberellin to produce seedless watermelans.
43
A gardener finds some broad-leaved dicot weeds growing in his lawns. What can be done to get rid of the weeds efficiently?
Explanation
The broad leaved dicot weeds can be killed and eliminated by the spray of weedicide 2-4 D, (a kind of plant phytohormone auxin). This will make the lawn free of weeds and will help the gardener, to make the lawn weed free.
44

On germination a seed first produces shoots with leaves, flowers appear later,

A. Why do you think this happens?

B. How is this advantageous to the plant?

Explanation

A. As soon as seed germinates, the plant enters into vegetative growth period. This period takes light stimulus (a critical length of light exposed to different plant, i.e., photoperiod) and synthesise the florigen (a flowering hormone) which induce flowering.

B. The vegetative growth period prepares the plant to bear reproductive structures like flower, fruits and seeds, and allows it to grow, mature and reproduce.

45

Fill in the blanks

A. Maximum growth is observed in ............. phase.

B. Apical dominance is due to ............

C. ........... initiate rooting .

D. Pigment involved in photoperception in flowering plants in ............ .

Explanation

A. Exponential

B. Auxin

C. Cytokinin

D. Phytochrome.

46
Some varieties of wheat are known as spring wheat while others are called winter wheat. Former variety is sown and planted in spring and is harvested by the end of the same season. However, winter varieties, if planted in spring, fail to flower or produce mature grains within a span of a flowering season. Explain, why?
Explanation

Some annual food plants such as wheat do not flower, unless they experience a low temperature. They remain vegetative during spring (warm period) but grow further to bear flowers and fruits after receiving low temperature (in winter).

The low temperature in winter prevents precocious reproductive development in autumn, thus enabling the plant to reach vegetative maturity before reproductive phase.

Thus, when spring varieties are planted in spring, they flower and bear fruits prion to end of growing season. But, if the winter varieties are planted in spring, they fail to flower and produce mature grains before the end of growing season, as they could not perceive low temperature of winters.

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