Influence of soil water content and atmospheric conditions on leaf water potential in cv. "Touriga Nacional" deep-rooted vineyards

Abstract In this study, the influence of soil and atmosphere conditions on noon and basal leaf water potential of vines ‘‘Touriga Nacional’’ in the Da˜o region submitted to different irrigation treatments is analysed. Both indicators showed to be dependent on environmental conditions at the time of measurement. Leaf water potential at noon of fully watered plants was linearly related with atmospheric conditions, with values registered when vapour pressure deficit (VPD) was higher than approximately 3 kPa being no different from the values registered in stressed plants. Therefore, this indicator cannot be reliably used to distinguish different plant water stress levels when atmospheric conditions induce high evaporative demands. The basal leaf water potential (wb) was also influenced by VPD at the time of measurement for all soil water conditions. In well irrigated plants, it was even possible to establish a baseline that can therefore be used to identify nonwater stressed conditions (wb (MPa) = -0.062–0.0972 VPD (kPa), r2 = 0.78). A good correlation was found between soil humidity and wb. However, more than the average value of the whole thickness of soil monitored, the wb values were dependent on the distribution of soil humidity, with the plants responding to the presence of wet layers

Stable-isotope techniques to investigate sources of plant water

Stable isotopologues of water (mainly 1H216O, HD16O and 1H218O) have been used for decades as tracers of the Earth's water cycle. In this chapter, we briefly describe the theoretical background and state-of-the-art techniques of the use of water stable isotopes to investigate the sources of plant water. We aim to provide the basic understanding of stable isotope fractionation within the Earth's critical zone that is relevant for studies of plant water sources. We then present a practical guide of their most common applications in field studies and the most common and up-to-date laboratory procedures. We finally introduce the existing statistical approaches for estimating the relative contributions of water sources to plant transpiration. By acknowledging the advantages and limitations of each approach, we aim to provide an overview of the current techniques to researchers in the fields of plant ecophysiology, ecohydrology and forest ecology, so that they can make informed decisions when designing their experiments

Ecomorphological plasticity of juvenile fall-run chinook salmon (Oncorhynchus tshawytscha) in perennial and ephemeral streams

In the Central Valley of California, environmental characteristics differ between perennial and ephemeral stream types and therefore present different challenges for rearing salmonids with respect to water discharge, water temperature, food availability, and habitat complexity. Body shape of juvenile fall-run Chinook salmon (Oncorhynchus tshawytscha) reared in a perennial stream environment was compared to juveniles reared in an ephemeral stream environment. Using geometric morphometrics and multivariate analyses, this study presents morphological differences of rearing juvenile Chinook salmon both within and between ephemeral and perennial stream types. We found that shape differences between stream types were primarily associated with expansion of the mid-body region relative to differences in body length. Specifically, juvenile Chinook salmon reared in the ephemeral stream expressed increased body depth dominated by dorsal-ventral elongation of the dorsal, adipose, and anal fins. Eye position and gill opercula-body insertion points also were anteriorly shifted in the juvenile body shape of the ephemeral stream. Our findings support that juvenile Chinook salmon are morphologically flexible and can express habitat-specific developmental differences

Risk assessment of ozone impact on Fagus crenata in Japan: consideration of atmospheric nitrogen deposition

Tropospheric ozone (O3) is considered to be the air pollutant relating to the decline of Fagus crenata forest in Japan. In the present study, we assessed a risk of O3 impact on the growth of F. crenata in Japan, giving consideration to the effects associated with atmospheric nitrogen (N) deposition based on the experimental study, national monitoring data for oxidant concentration and atmospheric N deposition, and a national vegetation survey. The average and maximum O3-induced relative growth reduction (RGred) of F. crenata across Japan were estimated to be 3.2 and 9.7%, respectively. Current levels of atmospheric N deposition were found to significantly affect the sensitivity of F. crenata to O3. When the N deposition was assumed as zero, the estimated average and maximum RGred were 2.3% and 5.7%, respectively. The inclusion of atmospheric N deposition data thus increased the estimated values for average and maximum RGred (by 38% and 71%, respectively). Our results demonstrate that a change in the sensitivity to O3 associated with atmospheric N deposition is an important consideration in the risk assessment of O3 impact on the growth of F. crenata in Japan