Diurnal and seasonal changes of leaf lamina hydraulic conductance in bur oak (Quercus macrocarpa) and trembling aspen (Populus tremuloides)

Abstract

The aim of this study was to examine the diurnal and seasonal variations in the sensitivity of leaf lamina (K lam ) hydraulic conductance to irradiance in bur oak (Quercus macrocarpa Michx.) and trembling aspen (Populus tremuloides Michx.), which vary in their responses of K lam to irradiance. K lam was determined using the highpressure method and the measurements were carried out in June, August and September. The irradiance response of K lam in bur oak was present throughout the day and declined in senescing leaves. In trembling aspen, K lam declined from morning to late afternoon and drastically decreased before the onset of leaf senescence, but it was not sensitive to irradiance. In both tree species, the capacity of the petioles to supply water to leaf lamina changed during the day in accordance with the ability of the leaf lamina to transport water. Petiole hydraulic conductivity (K pet ) declined during the season in bur oak leaves, while it tended to increase in trembling aspen leaves. There was no correlation between the K lam values and air temperature or light intensity at the time of leaf collection. For trembling aspen, K pet was negatively correlated with the air temperature suggesting sensitivity to drought. We conclude that the water transport properties of petioles and leaf lamina in the two studied tree species reflect their ecological adaptations. Trembling aspen leaves have high hydraulic conductivity and high stomatal conductance regardless of the irradiance level, consistent with the rapid growth and high demand for water. In contrast, the increased lamina hydraulic conductivity and stomatal conductance under high irradiance in bur oak trees reflect a water conservation strategy.

Developmental and Environmental Regulation of Aquaporin Gene Expression across Populus Species: Divergence or Redundancy?

“…The only regulation of the stem-preferred PtXIP1;4 was detected during winter hardening, opening new hypotheses. As in other species [58], [59], poplar AQP expression generally varied around the day (Figure S7B). Evidence of diurnal regulation was found, even if AQP expressions were often inconsistent across genotypes (Table 2).…”

Size-dependent variability of leaf and shoot hydraulic conductance in silver birch

“…All functional and structural characteristics measured in the study are listed in Table 1. It is important to separate K lb and K P , since K P can undergo changes that are independent of K lb (Voicu and Zwiazek 2011). Tyree et al (2005) indicated that stomatal openness does not influence results of the hydraulic measurements using a high-pressure flow meter.…”

“…Responses of K L to both temperature (Matzner and Comstock 2001;Sack et al 2004;Cochard et al 2007;Sellin and Kupper 2007b) and light Sack and Holbrook 2006;Scoffoni et al 2008;Voicu and Zwiazek 2011) have been extensively studied during the last decade. Rapid enhancing effects of increasing temperature and light intensity on leaf hydraulic conductance rely on changes in living extra-vascular tissues.…”

Combined impacts of irradiance and dehydration on leaf hydraulic conductance: insights into vulnerability and stomatal control

“…2009; Sellin et al . 2011; Voicu & Zwiazek 2011). Several authors proposed that the HPFM may be partly or totally responsible for this response, by opening new liquid flow pathways through the stomata, which open under high irradiance (Sack et al .…”