Question

Various forms of gibberellins are abundant during which stage of fruit development?

• A. Stage I
• B. Stage II
• C. Stage I \& Stage II
• D. Through out seed development

Hint:

Plant hormones regulate fruit development:
Stage I (Cell division): Auxins, Cytokinins are key.
Stage II (Cell enlargement/growth): Gibberellins are very important for promoting cell expansion and overall fruit size.
Stage III (Ripening): Ethylene, Abscisic acid become more dominant. Gibberellins are particularly abundant during active fruit growth and cell expansion phases.

Answer 1

The Correct Option is B

Fruit development is often described in stages, particularly for fruits showing a sigmoid or double sigmoid growth curve. For example, in a double sigmoid curve (common in stone fruits, grapes, guava):
Stage I (Cell Division): Rapid growth due to cell division and some cell enlargement. Auxins and cytokinins are often high.
Stage II (Cell Enlargement/Lag Phase for stone fruits, Pit Hardening): In stone fruits, this is a period of slow flesh growth but rapid embryo and endosperm development, and pit hardening. In berries like grapes, this can be a period of berry enlargement before veraison. Gibberellins (GAs) play a crucial role in cell elongation and overall fruit growth. The levels of active GAs are often found to be high during periods of rapid cell expansion and fruit sizing, which can correspond to parts of Stage I and significantly into Stage II (or the main cell expansion phase if considering a single sigmoid curve).
Stage III (Ripening/Second Rapid Growth): Cell enlargement continues, sugars accumulate, and ripening processes occur, often influenced by ethylene and abscisic acid. Gibberellins are known to be particularly abundant and active during phases of rapid cell elongation and fruit growth.
Option (1) Stage I: GAs are present and active, but auxins and cytokinins are also very dominant for cell division.
Option (2) Stage II: This stage, especially when referring to the period of major cell expansion and fruit sizing (which might be Stage II in a double sigmoid curve of berries, or encompasses the main growth after cell division), is strongly associated with high gibberellin activity. GAs promote cell enlargement, which is a key component of fruit growth.
Option (3) Stage I \& Stage II: GAs are indeed active in both, but their peak role in driving fruit size via cell expansion is very significant in Stage II or its equivalent.
Option (4) Throughout seed development: Seeds are a major site of GA synthesis, and GAs from seeds can influence fruit development. So, GAs are present during seed development, which often parallels fruit growth. Given the options, "Stage II" is often highlighted as a period where gibberellins play a very prominent role in driving the increase in fruit size through cell enlargement, especially after the primary cell division phase of Stage I. If the "Chosen option" is Stage II, it emphasizes this role. Stage II

Answer 2

Growth-curve approach:
Consider the classic double-sigmoid growth curve typical of many fruits. Stage I is dominated by rapid cell division, a process primarily driven by auxins and cytokinins rather than gibberellins. Stage III is the ripening phase, governed mainly by ethylene and abscisic acid. That leaves Stage II, the phase of major cell enlargement and fruit sizing, as the period when gibberellins are the principal active hormone, since GAs are specifically known for promoting cell elongation rather than division or ripening. Matching each stage to its dominant hormone class places peak gibberellin abundance in Stage II.