Chlorophyll fluorescence performance of sweet almond [Prunus dulcis (Miller) D. Webb] in response to salinity stress induced by NaCl

One-year old sweet almond (Prunus dulcis) seedlings were submitted to four levels of salt stress induced by NaCl, namely 0.3, 0.5, 0.7, and 1.0 S m(-1). Effects of salt stress on a range of chlorophyll (Ch1) fluorescence parameters (Ch1 FPs) and Ch1 contents were investigated in order to establish an eco-physiological characterization of P. dulcis to salinity. Salt stress promoted an increase in F-0, F-s, and F-0/F-m and a decrease in F-m, F'(m), F-v/F-m, q(p), Delta F/F'(m), F-v/F-0, and UQF((rel)), in almost all Ch1 fluorescence yields (FY) and FPs due to its adverse effect on activity of photosystem 2. No significant changes were observed for quenchings q(N), NPQ, and q(N(rel)). The contents of Ch1 a and b and their ratio were also significantly reduced at increased salt stress. In general, adverse salinity effects became significant when the electric conductivity of the nutrient solution (ECn) exceeded 0.3 S m(-1). The most sensitive salt stress indicators were F-v/F-0 and Ch1 a content, and they are thus best used for early salt detection in P. dulcis. Monitoring of a simple Ch1 FY, such as F-0, also gave a good indication of induced salt stress due to the significant correlations observed between the different Ch1 FYs and FPs. Even essential Ch1 FYs, like F-0, F-m, F'(m), and F-s, and mutually independent Ch1 FPs, like F-v/F-0 and q(P), were strongly correlated with each other

Osmotic stress affects physiological responses and growth characteristics of three pistachio cultivars

Pistachio (Pistacia vera L.) has a high tolerance to drought and soil salinity. Although adult pistachio trees are well known to be drought tolerant, the studies on physiological adaptation of pistachio cultivars to drought are limited. Therefore, three pistachio cultivars, i.e., Akbari, Kaleghochi, and Ohadi were subjected to three osmotic drought stress treatments: control (-0.1 MPa), moderate (-0.75 MPa) and severe drought (-1.5 MPa) stress using PEG 6000 for a 14-day period. All drought stress treatments decreased net photosynthesis (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E), but Ohadi maintained better its photosynthetic capacity compared to Akbari and Kaleghochi. Maximum quantum yield of PSII photochemistry (Fv/Fm), effective PSII quantum yield (UPSII) and photochemical quenching (qP) were also reduced. The chlorophyll fluorescence parameters indicated that Akbari was more susceptible to the applied drought stress. Drought stress levels decreased chlorophyll pigments, fresh weight, stem elongation, leaf nitrogen content (N), leaf water potential and increased water use efficiency (WUE). Proline increased strongly under drought stress for Akbari. After 2 weeks of stress a recovery of 2 weeks was applied. This period was insufficient to fully restore the negative effects of the applied stress on the studied cultivars. Based on the reduction of photosynthesis and the increase of the proline content Akbari seems more sensitive to the applied drought stress

Impact of water deficit on physiological parameters, bioactive content and antioxidant activity of three olive cultivars

We studied changes in morphology, sclerophylly, chlorophyll photosynthetic parameters and total phenol contents in leaves of three olive (Olea europaea L.) cultivars; Oueslati, Jarboui and Meski which grew under water deficit conditions. Our results showed significant differences in trichome and stomatal densities, area of the leaf and relative surface of stomatal pores. The photosynthetic parameters Fv/Fm, ΦPSII and ETR were negatively affected by the water deficit in these three varieties. The total phenolic and flavonoid contents increased in all cultivars, with Oueslati showing the highest values. The Oueslati variety could be considered as the most drought-tolerant compared to Jarboui and Meski. Therefore we believe this cultivar is the most suitable for cultivation in semi-arid environments