On the minimum leaf conductance: its role in models of plant water use, and ecological and environmental controls

Abstract

Contents Summary I. Introduction II. Comparison of various definitions and measurement techniques of minimum conductance III. Cuticular conductance IV. Contribution of stomata V. Environmental and ecological variation in minimum conductance VI. Use of minimum conductance in models VII. Conclusions Acknowledgements References SUMMARY: When the rate of photosynthesis is greatly diminished, such as during severe drought, extreme temperature or low light, it seems advantageous for plants to close stomata and completely halt water loss. However, water loss continues through the cuticle and incompletely closed stomata, together constituting the leaf minimum conductance (g ). In this review, we critically evaluate the sources of variation in g , quantitatively compare various methods for its estimation, and illustrate the role of g in models of leaf gas exchange. A literature compilation of g as measured by the weight loss of detached leaves is presented, which shows much variation in this trait, which is not clearly related to species groups, climate of origin or leaf type. Much evidence points to the idea that g is highly responsive to the growing conditions of the plant, including soil water availability, temperature and air humidity - as we further demonstrate with two case studies. We pay special attention to the role of the minimum conductance in the Ball-Berry model of stomatal conductance, and caution against the usual regression-based method for its estimation. The synthesis presented here provides guidelines for the use of g in ecosystem models, and points to clear research gaps for this drought tolerance trait.

Desiccation time during drought is highly predictable across species of Eucalyptus from contrasting climates

“…By contrast, plant desiccation time was unrelated to the minimum conductance of individual leaves g min . This is consistent with previous work suggesting g min is highly responsive to growth conditions (Duursma et al ., ), although some studies have shown the adaptive value of low g min with respect to drought tolerance (Burghardt & Riederer, ; Brodribb et al ., ). Plant desiccation time was also unrelated to the RWC at g s90 and Ψ crit , and somewhat unexpectedly was unrelated to the span of RWC between these thresholds.…”

“…During drought, plants typically close their stomata as a first response to minimize water loss (Martin-StPaul et al, 2017;Li et al, 2018a). However, if drought persists, tension within the water-conducting xylem will increase as plants dehydrate via water loss through permeable leaf cuticles and leaky stomata (Kerstiens, 1996;Brodribb et al, 2014;Schuster et al, 2017;Duursma et al, 2019). Without relief, increasing xylem tension can cause cavitation and widespread embolism (air bubbles that block water transport), leading to hydraulic dysfunction and plant death (Tyree & Sperry, 1989).…”

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

“…Slope is set 13 for herbaceous vegetation and 9.5 for woody vegetation, respectively (Miner et al, ) (Miner et al, ). Intercept is set 0.01 umol·m −2 ·s −1 (Duursma et al, ) with a multiplicative water stress factor .…”

Day length regulates seasonal patterns of stomatal conductance in Quercus species

“…In particular, our analysis indicates that day-length regulation may be particularly important as affecting minimal conductance (g 0 ). There has been a large body of literature trying to understand the meaning of this parameter (see review by Duursma et al, 2019), as well as its drivers, and here we show, for the first time to our knowledge, that it could vary seasonally with photoperiod. Our results also hint that, in conifers, day-length responses could mediate the slope of stomatal models (g 1 ), but the generality of this claim remains to be tested because in the available dataset from the literature, there were only four conifer species.…”