Error 1: Confusing Ethylene with ABA as Stress Hormone

Wrong: "Ethylene is the stress hormone because it increases during stress." Correct: ABA is the designated "stress hormone." Ethylene increases during stress too, but is primarily associated with ripening and abscission, NOT specifically the stress response. ABA is specifically elevated by abiotic stresses (drought, salinity) and mediates stomatal closure as the primary stress response.

Error 2: Confusing Chemical Nature of Cytokinins

Wrong: "Cytokinins are terpenoids because they affect growth." Correct: Cytokinins are ADENINE DERIVATIVES (purines). Remember: Cytokinin → Cytokinesis → promotes cell division → the hormone that promotes DNA synthesis (cytokinesis) is derived from adenine (a DNA base). Gibberellins AND ABA are the terpenoids.

Error 3: SDP Need "Short Days" Not Long Nights

Wrong: "SDPs flower in summer because days are short in summer." Correct: SDPs flower when NIGHTS are LONG $\frac{autumn}{winter}$. The photoperiodic signal detected is the length of the uninterrupted DARK period, not the light period. Interrupting the dark period prevents SDP flowering even if the day is short. SDPs should really be called "long-night plants."

Error 4: All Auxin Concentrations Promote Growth

Wrong: "Auxin always promotes growth at any concentration." Correct: Auxin shows a dose-response: LOW concentrations promote growth; HIGH concentrations inhibit growth. The optimal concentration differs by organ: roots (most sensitive), buds (intermediate), stems (least sensitive). This differential sensitivity explains why 2,4-D kills dicots at field concentrations.

Error 5: GA Causes Parthenocarpy Only

Wrong: "Only gibberellins can induce parthenocarpy." Correct: BOTH auxins and gibberellins can induce parthenocarpy. Both are frequently tested as correct answers in questions about seedless fruit production. Neither one alone is exclusively responsible.

Error 6: Vernalization is About Light

Wrong: "Vernalization is the same as photoperiodism — both involve light responses." Correct: Vernalization requires COLD temperature (0–5°C), not light. Photoperiodism involves the ratio of LIGHT to DARK periods. They are completely different mechanisms. The signal for vernalization is cold; for photoperiodism it is photoperiod $\frac{light}{dark ratio}$.

Error 7: Pfr Promotes Flowering in All Plants

Wrong: "Pfr (active phytochrome) promotes flowering in all plants." Correct: Pfr promotes flowering in LDPs but INHIBITS flowering in SDPs. The same molecule has opposite effects depending on plant type.