Abiotic Stress Tolerance in Plants with Emphasizing on Drought and Salinity Stresses in Walnut - Abiotic Stress: Plant Responses and Applications in Agriculture - page 348

• Walnut roots are mainly distributed in the upper soil layers. Soil moisture is a key factor
regulating root growth and water uptake efficiency of the roots. The shallow roots lose
efficiency in water uptake during the dry season and the shift to uptake by deeper roots
does not fully compensate for the loss of uptake by shallow roots and is not able to prevent
water stress, which is characterized by increased percentage loss of xylem conductance
(PLC) in pre-dawn, reduced pre-dawn leaf water potential and transpiration during abiotic
stresses.
• Understanding the ability of genotypes to absorb essential elements is indicative of their
ability to withstand stress.
• Differences in antioxidative enzymes (such as SOD, APX, POD, PPO, LOX, PAO and CAT)
activities among walnut genotypes could be attributed to differences in the mechanisms
underlying oxidative stress injury and subsequent tolerance to abiotic stress.
• Higher proline accumulation observed in tolerant seedlings of walnut to osmotic stresses
was accompanied by higher activities of antioxidative emzymes (e.g. SOD, APX, POD and
CAT). These results suggest that proline accumulation could activate the antioxidative
defense mechanism in walnut trees.
• The degree of stress tolerance found in seedlings of some walnut varieties has been
characterized at various stages of growth. Identified stress-tolerant genotypes are candi‐
dates for further studies under longer periods of drought and field studies to determine
their suitability for areas with adverse environmental conditions, and eventually for use as
drought-tolerant rootstocks.
• Application of biotechnology tools for increasing tolerance to abiotic stresses in walnut is
underway. Some promising results have been reported under in-vitro conditions.
Author details
Kourosh Vahdati 1* and Naser Lotfi 2*
1 Department of Horticulture, College of Aburaihan, University of Tehran, Pakdasht, Teh‐
ran, Iran
2 Higher Educational Center of Miandoab, Urmia University, Urmia, Iran
References
[1] Boyer JS. Plant productivity and Environment. Science 1982; 218:443-448