Stress physiology of crops in deserts

  • Irrigating table grapes in arid regions with low quality water: Effects of salinity and excess boron
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Early ripening table grapes are an increasingly economically viable crop in arid and semi-arid regions. Table grape production is particularly attractive in arid regions where cultivation is dependant upon the availability of large amounts of irrigation water. Unfortunately, water resources in such areas are often limited and the salinity of available irrigation water tends to be high. The response of grapevines (Vitis vinifera L. cv. Sugraone) to salinity, excess boron (B) and combinations of the two were studied under controlled conditions in a number of lysimeter, pot and field experiments. In a lysimeter experiment, salinity reduced leaf scale transpiration and photosynthesis and both leaf and whole plant biomass production and (evapo)transpiration were found to be linearly related. Mortality of vines was dynamically associated with salinity level and time. Grapevine response to salinity was observed to involve two mechanisms: (i) a reduction in transpiration and growth which began as soon as salinity was experienced; and (ii) vine mortality which was correlated with salinity level, a sharp increase in Na and Cl content of leaves, and time. At lower salinities, the onset of mortality occurred later and death rates increased as the duration of exposure to salinity increased. For vines grown for four years in pots, B in solution at levels greater than 1.3 mg L-1 caused reduced growth (trunk size), reduced nodal lengths between leaves on branches, and increasing B caused severe visual toxicity symptoms including necrotic leaves. In spite of this, B in solution as high as 3.3 mg L-1 did not lead to reduced biomass production as measured by pruning weights or reduced fruit production as measured via harvest data. Increased salinity caused reduction in B accumulation in the vines.

Ben-Gal, A., Yermiyahu U, Shani U., Veste M. (2008): Irrigating table grapes in arid regions with low  quality water: effects of salinity and excess boron. Acta Horticulturae 792: 107-114.

  • Impact of  thermal stress and high vpd on gas exchange and chlorophyll fluorescence of Citrus grandis under desert conditions 

Citrus, native of subtropical and tropical regions in Eastern Asia became widely cultivated in areas with Mediterranean climate. In Israel, Citrus grandis, C. sinensis, C. limon and C. paradisi are major fruit crops of the coastal plain, where the mean annual rainfall ranges between 500 and 700 mm and average temperature at midday in the August is 30 °C. During recent years cultivation of Citrus has substantially increased under desert conditions in the Negev and in the Arava Valley of Israel. In these arid areas crop production requires intensive irrigation. The climate of the Arava is characterized by mild winters and very hot summers with high air temperatures (> 42 °C), low air humidity and high radiation. The photosynthetic response of Citrus grandis to high light intensities, low air humidity and high temperature stress was investigated under desert conditions in the southern AravaValley (Israel). During summer, a typical midday stomatal closure was observed even in well-watered trees due to the dramatic increase of the leaf-to-air water vapour deficit. As a result of the reduced transpirational cooling, leaf temperatures increased up to 11 °C above ambient air temperature. The combination of heat stress and photoinhibition resulted in a reversible decrease of photosynthetic activity of Citrus grandis under the extreme summer conditions.

Veste, M., Ben-Gal, A., Shani, U. (2000): Impact of  thermal stress and high vpd on gas exchange and chlorophyll fluorescence of Citrus grandis under desert conditions. Acta Horticulturae 531: 143-149.

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