English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Understanding seasonal changes in photosynthetic parameters and stomatal conductance is crucial for modeling long-term carbon uptake and energy fluxes of ecosystems. Gas exchange measurements of CO2 and light response curves on blue oak leaves (Quercus douglasii H. &amp; A.) were conducted weekly throughout the growing season to study the seasonality of photosynthetic capacity (Vcmax) and Ball-Berry slope (m) under prolonged summer drought and high temperature. A leaf photosynthetic model was used to determine Vcmax. There was a pronounced seasonal pattern in Vcmax. The maximum value of Vcmax, 127 micromol m(-2) s(-1), was reached shortly after leaf expansion in early summer, when air temperature was moderate and soil water availability was high. Thereafter, Vcmax declined as the soil water profile became depleted and the trees experienced extreme air temperatures, exceeding 40 degrees C. The decline in Vcmax was gradual in midsummer, however, despite extremely low predawn leaf water potentials (Psipd, approximately -4.0 MPa). Overall, temporal changes in Vcmax were well correlated with changes in leaf nitrogen content. During spring leaf development, high rates of leaf dark respiration (Rd, 5-6 micromol m(-2) s(-1)) were observed. Once a leaf reached maturity, Rd remained low, around 0.5 micromol m(-2) s(-1). In contrast to the strong seasonality of Vcmax, m and marginal water cost per unit carbon gain (partial partial differential E/ partial partial differential A) were relatively constant over the season, even when leaf Psipd dropped to -6.8 MPa. The constancy of partial partial differential E/ partial partial differential A suggests that stomata behaved optimally under severe water-stress conditions. We discuss the implications of our findings in the context of modeling carbon and water vapor exchange between ecosystems and the atmosphere.

tree physiology

Seasonal trends in photosynthetic parameters and stomatal conductance of blue oak (Quercus douglasii) under prolonged summer drought and high temperature