Mechanisms of Acclimation of Photosynthesis and Leaf Growth to Water Deficits in Sunflower

Repeated water deficits can alter the response of photosynthesis and leaf growth to subsequent water deficits, but the mechanisms by which these changes occur are unknown. This study was conducted to evaluate the mechanisms by which photosynthesis and leaf growth acclimate to low leaf water potential ((psi)(,l)). The response of photosynthesis to (psi)(,l), determined from gas-exchange and isopiestic thermocouple psychrometry, was shifted 3 to 4 bars towards lower (psi)(,l) in plants grown under a mild soil water deficit. Both stomata and chloroplasts contributed to the acclimation. Leaf diffusive resistance at low (psi)(,l) was less in acclimated plants than control plants. Chloroplast activity, demonstrated in situ with measurements of quantum yield, capacity to fix CO(,2) at all partial pressures of CO(,2) (pCO(,2)), and in the isolated organelle with measurements of photosystem II electron transport, was inhibited less at low (psi)(,l) in the acclimated plants than in the control plants. Analysis of the acclimation indicated that altered chloroplast sensitivity contributed more than altered stomatal response to the acclimation of photosynthesis to low (psi)(,l).

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Agronomy

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

1983

Author dc:creator

• Matthews, Mark Allen

• Biology, Plant Physiology

Identifier

(UMI)AAI8324601

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71584