Drought Stress and the Recovery from Xylem Embolism in Woody Plants

Holm oak (Quercus ilex L.) is a Mediterranean species that can withstand intense summer drought through a high resistance to cavitation far beyond the stomatal closure. Besides stomatal limitations, both mesophyll and biochemical limitations to CO2 uptake could increase in holm oak under drought. However, no studies have addressed how hydraulic and non-hydraulic factors may limit the recovery of photosynthesis when re-watering after inducing 50% loss of hydraulic conductivity. We measured photosynthetic traits, xylem embolism, and abscisic acid (ABA) in holm oak with increasing levels of drought stress and seven days after plant re-watering. Drought stress caused a sharp decrease in net CO2 assimilation (AN), stomatal and mesophyll conductance (gs and gm), and maximum velocity of carboxylation (Vcmax). The stomatal closure could be mediated by the rapid increase found in ABA. The high level of xylem embolism explained the strong down-regulation of gs even after re-watering. Therefore, only a partial recovery of AN was observed, in spite of non-hydraulic factors not limiting the recovery of AN, because i/ABA strongly decreased after re-watering, and ii/gm and Vcmax recovered their original values. Therefore, the hydraulic-stomatal limitation model would be involved in the partial recovery of AN, in order to prevent extensive xylem embolism under subsequent drought events that could compromise holm oak survival.

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Response mechanisms of hydraulic systems of woody plants to drought stress

Chinese Journal of Plant Ecology ◽

10.17521/cjpe.2021.0111 ◽

2021 ◽

Vol 45 (9) ◽

pp. 925-941

Author(s):

Dan-Dan LUO ◽

Chuan-Kuan WANG ◽

Ying JIN ◽

Keyword(s):

Drought Stress ◽

Woody Plants ◽

Hydraulic Systems

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Drought tolerance of wild versus cultivated tree species of almond and plum in the field

Tree Physiology ◽

10.1093/treephys/tpz134 ◽

2019 ◽

Vol 40 (4) ◽

pp. 454-466

Author(s):

Indira Paudel ◽

Hadas Gerbi ◽

Yael Wagner ◽

Annat Zisovich ◽

Gal Sapir ◽

...

Keyword(s):

Drought Stress ◽

Drought Tolerance ◽

Tree Species ◽

Prunus Dulcis ◽

Prunus Domestica ◽

Xylem Embolism ◽

Wild Tree ◽

In The Wild ◽

Almond Trees ◽

Wild Almond

Abstract Trees of the genus Prunus produce some of the most widely consumed fruits globally. The combination of climate change-related warming and increased drought stress, scarcity of freshwater resources for irrigation, and increasing demands due to population growth creates a need for increased drought tolerance in these tree species. Recently, we have shown in the field that a native wild pear species performs better under drought than two cultivated pear species. Here, a comparative field study was conducted in Israel to investigate traits associated with drought tolerance in almond (cultivated Prunus dulcis (Mill.) D. A. Webb vs wild Prunus ramonensis Danin) and plum (cultivated Prunus domestica L. vs wild Prunus ursina Kotschy). Measurements of xylem embolism and shoot and root carbon reserves were done along a year, including seasonal drought in the wild and a 35-day drought experiment in the orchards. Synchronous measurements of native xylem embolism and shoot water potential showed that cultivated and wild almond trees lost ~50% of hydraulic conductivity at −2.3 and −3.2 MPa, respectively. Micro-CT images confirmed the higher embolism ratio in cultivated versus wild almond, whereas the two plum species were similar. Dynamics of tissue concentrations of nonstructural carbohydrates were mostly similar across species, with higher levels in cultivated versus wild plum. Our results indicate an advantage for the wild almond over its cultivated relative in terms of xylem resistance to embolism, a major risk factor for trees under drought stress. This result is in line with our previous experiment on pear species. However, the opposite trends observed among the studied plum species mean that these trends cannot be generalized. It is possible that the potential for superior drought tolerance in wild tree species, relative to their cultivated relatives, is limited to wild species from dry and hot habitats.

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Transcriptional Regulation of Drought Response in Arabidopsis and Woody Plants

Frontiers in Plant Science ◽

10.3389/fpls.2020.572137 ◽

2021 ◽

Vol 11 ◽

Author(s):

Tao Yao ◽

Jin Zhang ◽

Meng Xie ◽

Guoliang Yuan ◽

Timothy J. Tschaplinski ◽

...

Keyword(s):

Transcriptional Regulation ◽

Drought Stress ◽

Woody Plants ◽

Woody Species ◽

Drought Response ◽

Nuclear Factor ◽

Ecological Processes ◽

Adverse Conditions ◽

Nuclear Factor Y ◽

Responsive Element

Within the context of global warming, long-living plants such as perennial woody species endure adverse conditions. Among all of the abiotic stresses, drought stress is one of the most detrimental stresses that inhibit plant growth and productivity. Plants have evolved multiple mechanisms to respond to drought stress, among which transcriptional regulation is one of the key mechanisms. In this review, we summarize recent progress on the regulation of drought response by transcription factor (TF) families, which include abscisic acid (ABA)-dependent ABA-responsive element/ABRE-binding factors (ABRE/ABF), WRKY, and Nuclear Factor Y families, as well as ABA-independent AP2/ERF and NAC families, in the model plant Arabidopsis. We also review what is known in woody species, particularly Populus, due to its importance and relevance in economic and ecological processes. We discuss opportunities for a deeper understanding of drought response in woody plants with the development of high-throughput omics analyses and advanced genome editing techniques.

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