Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Tuberization in sweet potato is almost absent at 75 % shade and severely affected at 55 % and not much affected at 25 % shade.
Reason (R) : Warm sunny days and cool nights are favourable for better tuber development in sweet potato.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Sweet potato needs a lot of sun for good tuber formation because tubers are stored carbohydrates from photosynthesis. Shade reduces sunlight, thus reducing tuberization (Assertion A).
Warm sunny days (for lots of photosynthesis) and cool nights (to reduce sugar use by the plant itself) are ideal for sweet potato tuber growth (Reason R).
The reason explains the assertion: if sunny days are needed, then lack of sun (shade) will be harmful.

Answer 1

The Correct Option is A

Assertion (A): Tuberization in sweet potato is almost absent at 75 % shade and severely affected at 55 % and not much affected at 25 % shade. This statement is true. Sweet potato (Ipomoea batatas) is a sun-loving plant. Tuberization (formation of storage roots) is highly dependent on photosynthesis, which produces the carbohydrates stored in the tubers. Shading reduces light intensity, thereby reducing photosynthesis.
High levels of shade (like 75%) significantly reduce carbohydrate production, leading to poor or absent tuberization.
Moderate shade (like 55%) will also severely affect tuber yield.
Low levels of shade (like 25%) will have a less pronounced effect, though full sun is optimal. Reason (R): Warm sunny days and cool nights are favourable for better tuber development in sweet potato. This statement is true.
Warm sunny days: Maximize photosynthesis, leading to high production of sugars (carbohydrates).
Cool nights: Reduce respiration rates. Lower night temperatures mean less of the photosynthates produced during the day are consumed by the plant for maintenance respiration. This allows more carbohydrates to be translocated and stored in the developing tubers. This combination of conditions promotes a net accumulation of carbohydrates, which is essential for good tuber development. Is (R) the correct explanation of (A)? Yes, (R) helps explain (A). The assertion (A) describes how lack of sunlight (shade) negatively impacts tuberization. The reason (R) highlights that "warm sunny days" are favorable for tuber development because they are essential for photosynthesis. Shade directly reduces the "sunny days" aspect. If photosynthesis is reduced due to shade, then even if night temperatures are cool, there are fewer carbohydrates available for storage, thus explaining the poor tuberization under shade described in (A). The requirement for ample sunlight (as implied by R being favorable) directly links to why shade (lack of sunlight) is detrimental (as stated in A). Therefore, both statements are true, and (R) provides the physiological basis (need for high photosynthesis from sunny days) that explains why shade (which reduces photosynthesis) is detrimental to tuberization. Both (A) and (R) are true and (R) is the correct explanation of (A).