Question

Regarding the plant species requiring a drop in nightly temperature for survival, what plausible explanation could be linked to the metabolic processes leading to plant death during warm nights?

A) Abscisic acid production leading to stomatal closure, hindering CO2 uptake and photosynthesis.
B) The breakdown of stored energy reserves being expedited during warm nights, causing overexpenditure and eventual death.
C) Extension of the photo period to counteract the metabolic strain caused by warm nights.
D) Synthesis of abscisic acid by alpine plants in response to high nighttime temperatures.

Answer 1

A plausible explanation for plant death during warm nights involves the stomatal closure due to high temperatures, which hinders CO2 uptake and photosynthesis. Abscisic acid, important in dormancy, and Crassulacean Acid Metabolism (CAM) pathways are adversely affected, leading to overstressed energy reserves or disrupted dormancy cycles.

Step-by-step explanation:

Plants that require a drop in nightly temperature for survival may face metabolic challenges during warm nights which can lead to their death. One plausible explanation for this could be linked to the absence of sufficient CO2 uptake and the hindrance of photosynthesis due to the stomatal closure, which occurs as a response to warm temperatures. Abscisic acid (ABA) plays a role in this process; it induces dormancy and causes stomata to close to minimize water loss, particularly in dry conditions or when soil moisture is low. However, temperate climate plants require cool temperatures for ABA to break down during winter, to release seeds from dormancy and ensure proper timing for germination.

During warm nights, processes like Crassulacean Acid Metabolism (CAM) cannot occur as effectively. CAM plants, such as cacti, typically fix CO2 at night when temperatures are cooler, conserving water in the process. If night temperatures remain high, these plants might overuse their stored energy reserves, leading to expedited energy consumption and eventual death. Furthermore, high nighttime temperatures can also interrupt the dormancy cycles regulated by ABA, affecting seed germination as well as budding processes in plants adapted to colder climates.