Responses of two Acacia species to drought suggest different water-use strategies, reflecting their topographic distribution

Daphna Uni; Efrat Sheffer; Tamir Klein; Rachamim Shem-Tov; Nitzan Segev; Gidon Winters

doi:10.3389/fpls.2023.1154223

Responses of two Acacia species to drought suggest different water-use strategies, reflecting their topographic distribution

Front Plant Sci. 2023 Jun 5:14:1154223. doi: 10.3389/fpls.2023.1154223. eCollection 2023.

Authors

Daphna Uni^{1

2}, Efrat Sheffer¹, Tamir Klein², Rachamim Shem-Tov³, Nitzan Segev³, Gidon Winters^{3

4}

Affiliations

¹ Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
² Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
³ Acacia Research Center, The Dead Sea-Arava Science Center, Masada, Israel.
⁴ Department of Life Sciences, Ben-Gurion University of the Negev, Eilat, Israel.

Abstract

Introduction: Soil water availability is a key factor in the growth of trees. In arid deserts, tree growth is limited by very dry soil and atmosphere conditions. Acacia tree species are distributed in the most arid deserts of the globe, therefore they are well adapted to heat and long droughts. Understanding why some plants do better than others in some environments is a key question in plant science.

Methods: Here we conducted a greenhouse experiment to continuously and simultaneously track the whole-plant water-balance of two desert Acacia species, in order to unravel their physiological responses to low water availability.

Results: We found that even under volumetric water content (VWC) of 5-9% in the soil, both species maintained 25% of the control plants, with a peak of canopy activity at noon. Moreover, plants exposed to the low water availability treatment continued growing in this period. A. tortilis applied a more opportunistic strategy than A. raddiana, and showed stomatal responses at a lower VWC (9.8% vs. 13.1%, t₄= -4.23, p = 0.006), 2.2-fold higher growth, and faster recovery from drought stress.

Discussion: Although the experiment was done in milder VPD (~3 kPa) compared to the natural conditions in the field (~5 kPa), the different physiological responses to drought between the two species might explain their different topographic distributions. A. tortilis is more abundant in elevated locations with larger fluctuations in water availability while A. raddiana is more abundant in the main channels with higher and less fluctuating water availability. This work shows a unique and non-trivial water-spending strategy in two Acacia species adapted to hyper-arid conditions.

Keywords: Acacia trees; desert; drought; plantarray; transpiration.

Grants and funding

GW thanks the Arava Drainage Authority and the Israeli Ministry of Science and Technology (MOST) for their continued support. DU was funded by the Ariovich scholarship and by the scholarship of the advanced school for environmental studies of the Hebrew University. TK is funded by the Benoziyo Fund for the Advancement of Science; Mr. and Mrs. Norman Reiser, together with the Weizmann Center for New Scientists; and the Edith & Nathan Goldberg Career Development Chair. ES was funded by the Ring Center for Environmental Research grant, and by an Israel-Italy collaboration grant of the Israeli Ministry of Science and Technology.