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 (Chl) fluorescence parameters (Chl FPs) and Chl contents were investigated in order to establish an eco-physiological characterization of P. dulcis to salinity. Salt stress promoted an increase in F0, Fs, and F0/Fm and a decrease in Fm, F'm, Fv/Fm, qP, ΔF/F'm, Fv/F0, and UQF(rel), in almost all Chl fluorescence yields (FY) and FPs due to its adverse effect on activity of photosystem 2. No significant changes were observed for quenchings qN, NPQ, and qN(rel). The contents of Chl 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 Fv/F0 and Chl a content, and they are thus best used for early salt detection in P. dulcis. Monitoring of a simple Chl FY, such as F0, also gave a good indication of induced salt stress due to the significant correlations observed between the different Chl FYs and FPs. Even essential Chl FYs, like F0, Fm, F'm, and Fs, and mutually independent Chl FPs, like Fv/F0 and qP, were strongly correlated with each other. and A. Ranjbarfordoei, R. Samson, P. Van Damme.
The effects of drought stress induced by polyethylene glycol, PEG (molecular mass 6000) on some ecophysiological characteristics of two wild pistachio species, Mastic and Khinjuk (P. mutica and P. khinjuk) selected as root stocks for production of edible pistachio trees (P. vera) in Iran and Turkey, were studied. Net photosynthetic rate (PN), stomatal conductance (gs), chlorophyll (Chl) fluorescence parameters, leaf water potential (Ψ1), leaf osmotic potential (Ψπ), leaf osmotic adjustment (ΔΨπ), and Chl a and b were measured. All parameters were influenced by increase in concentra-tion of PEG in the nutrient solutions. PN, gs, and Chl a were significantly higher in P. mutica than in P. khinjuk but, compared to the control treatment, P. khinjuk showed a higher resistance to drought stress than P. mutica. and A. Ranjbarfordoei ... [et al.].
Leaf water potential, leaf osmotic potential, chlorophyll a and b contents, stomatal conductance, net photosynthetic rate, and water use efficiency were determined in two pistachio species (Pistacia khinjuk L. and P. mutica L.) grown under osmotic drought stress induced by a combination of NaCl and polyethylene glycol 6000. A decrease in values for all mentioned variables was observed as the osmotic potential of the nutrient solution (Ψs) decreased. The osmotic adjustment (ΔΨπ) of the species increased by decreasing Ψs. Thus P. khinjuk had a higher osmotic drought stress tolerance than P. mutica. and A. Ranjbarfordoei ... [et al.].
Due to anthropogenic influences, solar UV-B irradiance at the earth's surface is increasing. To determine the effects of enhanced UV-B radiation on photosynthetic characteristics of Prunus dulcis, two-year-old seedlings of the species were submitted to four levels of UV-B stress, namely 0 (UV-Bc), 4.42 (UV-B1), 7.32 (UV-B2) and 9.36 (UV-B3) kJ m-2 d-1. Effects of UV-B stress on a range of chlorophyll (Chl) fluorescence parameters (FPs), Chl contents and photosynthetic gas-exchange parameters were investigated. UV-B stress promoted an increase in minimal fluorescence of
dark-adapted state (F0) and F0/Fm, and a decrease in variable fluorescence (Fv, Fv/Fm, Fv/F0 and F0/Fm) due to its adverse effects on photosystem II (PSII) activity. No significant change was observed for maximal fluorescence of dark-adapted state (Fm). Enhanced UV-B radiation caused a significant inhibition of net photosynthetic rate (PN) at UV-B2 and UV-B3 levels and this was accompanied by a reduction in stomatal conductance (gs) and transpiration rate (E). The contents of Chl a, b, and total Chl content (a+b) were also significantly reduced at increased UV-B stress. In general, adverse UV-B effects became significant at the highest tested radiation dose 9.36 kJ m-2 d-1. The most sensitive indicators for UV-B stress were Fv/F0, Chl a content and PN. Significant P<0.05 alteration in these parameters was found indicating the drastic effect of UV-B radiation on P. dulcis. and A. Ranjbarfordoei ... [et al.].