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Practice each question, then open the answer or worked solution.
To get a carpet like grass lawns are mowed regularly. Is there any of scientific explanation for this?
Ans: While mowing, the apices of grass are removed. This helps in preventing apical dominance and in preventing longitudinal growth of grass. After removal of apices, auxins get mobilized to lateral buds and promote growth of lateral branches. This helps in giving carpet-like lawns.
In a slide showing different types of cells can you identify which type of the cell may be meristematic and the one which is incapable of dividing and how?
Ans: Different sorts of cells are depicted on a slide., presence of following characteristics would indicate meristematic cells:
a. Thin cell wall
b. Dense cytoplasm
c. Cells showing cell division.
d. Smaller vacuoles or negligible vacuoles. If above features are absent then the cells are incapable of division.
A rubber band stretches and reverts to its original position. Bubble gum stretches, but it would not return to its original position. Is there any difference between the two processes? Discuss it with respect to plant growth. [Hint: Elasticity (reversible) Plasticity (irreversible)]
Ans: From the theory of physics, we know that if a substance regains its original shape after the removal of deforming forces, the substance is said to exhibit elasticity. On the other hand, if a substance fails to regain its original shape after the removal of deforming forces, the substance is said to exhibit plasticity. In above examples; rubber band is showing elasticity. But bubble gum is showing plasticity.
Label the diagram
a. This is which part of a dicotyledonous plant?
b. If we remove part 1 from the plant, what will happen?
Ans: (a) This diagram shows the shoot apex.
Ans: Removal of part 1 will prevent apical dominance. This will help in growth of lateral branches.
Both animals and plants grow. Why do we say that growth and differentiation in plants is open and not so in animals? Does this statement hold true for sponges also?
Ans: In animals, once one type of tissue is developed, it cannot be changed into another. Furthermore, all organs of the animal's body stop growing at a specific age. Plant growth, in the other hand, is indeterminate since a plant component can develop into an unlimited number of numbers. In plants, a senescent component is frequently replaced. If a need arises, differentiated cells in plants undergo dedifferentiation. Sponges are an unusual animal in the animal realm. The growth of a sponge is open.
Define parthenocarpy. Name the plant hormone used to induce parthenocarpy.
Ans: Parthenocarpy is a condition that occurs when fruit develops without being fertilised. Bananas and some papaya kinds are parthenocarpic fruits, meaning they don't have seeds. Parthenocarpy can be induced by auxins and gibberellins.
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?
Ans: Watermelons with no seeds are always preferable. Watermelons can be induced to produce seedless fruits by inducing parthenocarpy. Auxin and gibberellins can be sprayed on watermelon plants to achieve this.
A gardener finds more broad-leaved dicot weeds growing in his lawns. What can be done to get rid of the weeds efficiently?
Ans: Spraying 2,4-D, a form of auxin, on the broad-leaved weeds will kill them. This is a synthetic auxin that farmers commonly use to control weeds.
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?
Ans: Initially, after seed germination, branches with leaves appear. This signifies the plant's vegetative development. This is necessary in order to synthesise sufficient nutrients for sexual reproduction. As a result, blossoming occurs after this stage.
Ans: The vegetative phase of growth aids in the maturation of the plant. A grown plant would be better able to tolerate the stresses of flowering and fruiting. As a result, the vegetative phase of growth aids in the survival of plant species.
Fill in the blanks:
a. Maximum growth is observe in ………… phase.
b. Apical dominance is due to …………
c. ………… initiate rooting.
d. Pigment involved in Photoperception in flowering plants is …………
Ans: Exponential
Ans: Auxin
Ans: Cytokinin
Ans: Phytochrome