Passive stomatal closure under extreme drought in an angiosperm species

Abstract

The phytohormone abscisic acid (ABA) plays a major role in closing the stomata of angiosperms. However, recent reports of some angiosperm species having a peaking-type ABA dynamic, in which under extreme drought ABA levels decline to pre-stressed levels, raises the possibility that passive stomatal closure by leaf water status alone can occur in species from this lineage. To test this hypothesis, we conducted instantaneous rehydration experiments in the peaking-type species Umbellularia californica through a long-term drought, in which ABA levels declined to pre-stress levels, yet stomata remain closed. We found that when ABA levels were lowest during extreme drought, stomata of U. californica were passively closed by leaf water status alone, with stomata reopening rapidly to maximum rates of gas exchange on instantaneous rehydration. This contrasts with leaves early in drought, in which ABA levels were highest and stomata did not reopen on instantaneous rehydration. The transition from ABA-driven stomatal closure to passively driven stomatal closure as drought progresses in this species occurs at very low water potentials facilitated by highly embolism-resistant xylem. These results have important implications for understanding stomatal control during drought in angiosperms.

Integrative Analysis of the DUF668 Gene Family in Nicotiana tabacum to Excavate Their Potential Roles in Abiotic Stress Responses

“…The analysis of gene expression under stress conditions, especially drought and salt stress, is crucial for understanding plant resilience mechanisms [38]. Plants have evolved complex strategies to cope with these stresses, involving physiological adaptations such as leaf reduction, stomatal closure, and the regulation of ion homeostasis [39][40][41]. Alterations in gene expression play a pivotal role in orchestrating these adaptive responses, ensuring plants can thrive in challenging environments.…”