Physiological and anatomical changes induced by drought in two olive cultivars (cv Zalmati and Chemlali)

Abstract

Photosynthetic gas exchange, vegetative growth, water relations and fluorescence parameters as well as leaf anatomical characteristics were investigated on young plants of two Olea europaea L. cultivars (Chemlali and Zalmati), submitted to contrasting water availability regimes. Twoyear-old olive trees, grown in pots in greenhouse, were not watered for 2 months. Relative growth rate (RGR), leaf water potential (W LW ) and the leaf relative water content (LWC) of the two cultivars decreased with increasing water stress. Zalmati showed higher values of RGR and LWC and lower decreased values of W LW than Chemlali, in response to water deficit, particularly during severe drought stress. Water stress also caused a marked decline on photosynthetic capacity and chlorophyll fluorescence. The net photosynthetic rate, stomatal conductance, transpiration rate, the maximal photochemical efficiency of PSII (F v /F m ) and the intrinsic efficiency of open PSII reaction centres (F 0 v /F 0 m ) decreased as drought stress developed. In addition, drought conditions, reduced leaf chlorophyll and carotenoids contents especially at severe water stress. However, Zalmati plants were the less affected when compared with Chemlali. In both cultivars, stomatal control was the major factor affecting photosynthesis under moderate drought stress. At severe drought-stress levels, the non-stomatal component of photosynthesis is inhibited and inactivation of the photosystem II occurs. Leaf anatomical parameters show that drought stress resulted in an increase of the upper epidermis and palisade mesophyll thickness as well as an increase of the stomata and trichomes density. These changes were more characteristic in cv. 'Zalmati'. Zalmati leaves also revealed lower specific leaf area and had higher density of foliar tissue. From the behaviour of Zalmati plants, with a smaller reduction in relative growth rate, net assimilation rate and chlorophyll fluorescence parameters, and with a thicker palisade parenchyma, and a higher stomatal and trichome density, we consider this cultivar more droughttolerant than cv. Chemlali and therefore, very promising for cultivation in arid areas.

Effect of deficit irrigation and growing seasons on plant water status, fruit yield and water use efficiency of squash under saline soil

“…Our results reported reductions in F v /F m , F v /F 0 and performance index (PI) under DI stress conditions, which were possibly due to the reduction in leaf photosynthetic pigments and RWC (Tables 5 and 6) needed for photosynthesis. These results are in parallel line with those of Gunes et al (2007), Boughalleb and Hajlaoui (2011) and Habibi (2012) concluding that decreasing F v /F m values implies that photochemical conversion efficiency could indicate the possibility of photo-inhibition. The reduction in chlorophyll concentrations due to osmotic stress has been ascribed to the strong damage and loss of chloroplast membranes (Kaiser et al, 1981).…”

Photosynthetic Properties and Response to Drought in Cucumber Seedlings Acclimatized to Different Vapor-pressure-deficit Levels

“…The leaf surface properties differed greatly between the treatments, even though the leaf areas were similar. The higher stomatal density and smaller stomatal size in the high-VPD leaves agrees with previous reports, in which stomatal density increased, but stomatal size decreased, under water stress in several species (Bosabalidis and Kofidis, 2002;Boughalleb and Hajlaoui, 2011;Hovenden et al, 2012). The higher stomatal density and smaller stomatal size influence g s an- tagonistically and compensate for each other.…”

Differential growth, physiological and biochemical responses of niger (Guizotia abyssinica Cass.) cultivars to water-deficit (drought) stress

“…These decreases were more remarkable in the presence of significant aggravation in the water-deficit treatments, i.e., at 20% PEG and 60% FC. On the basis of relative water content of the tissue, many workers have distinguished the genotypes of crop species as sensitive and tolerant (Hojati et al 2011;Boughalleb and Hajlaoui 2011). Similarly, in the present investigation, cultivar IGPN 2004 showed the highest water content as well as growth, which could be defined as the more tolerant cultivar to water-deficit stress.…”