Plant Growth And Development

The preservation of pollen grains as fossils in the deepest soil layer can be explained by analyzing the structural and chemical properties of pollen walls:

Key factors enabling pollen fossilization:

1. Exine composition: The outer wall (exine) of pollen grains contains sporopollenin, one of the most chemically resistant biological compounds known. This complex biopolymer is: - Highly resistant to enzymatic degradation - Stable under extreme temperature and pH conditions - Impervious to most microbial action - Chemically inert against most environmental factors

2. Intine properties: While the inner wall (intine) is pectin-cellulose based (option A), this layer decomposes readily and doesn't contribute to fossil preservation.

3. Ornamentation relevance: While exine may have spiny ornamentation (option B), this feature aids in species identification but doesn't affect preservation potential.

4. Reproductive nature: Pollen grains are sexual reproductive structures (making option D incorrect), but this characteristic doesn't influence fossilization.

Thus, the correct answer is (C) The exine of pollen grains is highly resistant to enzyme action.

Let's evaluate each statement about plant hormones and their applications:

1. "Kinetin is a derivative of Adenine which is a pyrimidine."
   • Kinetin is a synthetic cytokinin, a class of plant hormones that promote cell division. Its chemical structure is derived from Adenine.
   • Adenine is a nitrogenous base belonging to the Purine group (double-ring structure), not the Pyrimidine group (single-ring structure).
   • Therefore, the statement that Adenine is a pyrimidine is incorrect, making the entire statement incorrect.
2. "The technique of decapitation is widely used in tea plantations."
   • Decapitation refers to the removal of the apical bud (shoot tip).
   • The apical bud produces auxin, which causes apical dominance, suppressing the growth of lateral buds.
   • Removing the apical bud removes the auxin source, allowing lateral buds to grow, leading to a bushier plant.
   • This practice is common in tea plantations and hedge-making to encourage dense growth.
   • This statement is correct.
3. "Ethylene is a gaseous plant hormone."
   • Ethylene (C₂H₄) is unique among the major plant hormones as it is a gas at physiological temperatures.
   • It plays roles in fruit ripening, senescence, abscission, and stress responses.
   • This statement is correct.
4. "Use of GA₃ hastens the malting process in brewing industry."
   • GA₃ (Gibberellic Acid) promotes seed germination by stimulating the production of hydrolytic enzymes like α-amylase in the aleurone layer of cereal grains (like barley).
   • Malting involves the controlled germination of barley, where these enzymes break down stored starch into fermentable sugars.
   • Applying GA₃ speeds up enzyme synthesis and thus hastens the malting process.
   • This statement is correct.
5. "ABA is a growth promoter."
   • ABA (Abscisic Acid) generally acts as a plant growth inhibitor.
   • It promotes dormancy in seeds and buds, induces stomatal closure during water stress, and plays a role in senescence and abscission. It counteracts the growth-promoting effects of auxins and gibberellins in many situations.
   • This statement is incorrect.

The incorrect statements are 1 and 5.

Comparing this to the options:

• 1, 2, 3, 4
• Only 3
• 2, 3, 4
• 1 and 5

The correct option is 1 and 5.