Photosynthesis and photosystem 2 efficiency of two salt-adapted halophytic seashore Cakile maritima ecotypes

Abstract

The effects of salinity (0-400 mM NaCl, marked S 0 , S 100 , S 200 , and S 400 ) on growth, photosynthesis, photosystem 2 (PS2) efficiency, ion relations, and pigment contents were studied in two seashore Cakile maritima ecotypes (Tabarka and Jerba, respectively, sampled from humid and arid bioclimatic areas). Growth of Jerba plants was improved at S 100 as compared to S 0 . Tabarka growth was inhibited by salinity at all NaCl concentrations. Leaf sodium and chloride concentrations increased with medium salinity and were higher in Jerba than in Tabarka plants. Chlorophyll content, net photosynthetic rate, stomatal conductance (g s ), and intracellular CO 2 concentration were stimulated at moderate salinity (S 100 ) in Jerba plants and inhibited at higher salt concentrations in both ecotypes: g s was the most reduced parameter. The maximum quantum efficiency of PS2 (F v v v /F m m m ), quantum yield, linear electron transport rate, and efficiency of excitation energy capture by open PS2 reaction centres showed no significant changes with increasing salt concentration in Jerba plant and were decreased in Tabarka subjected to S 400 . However, the efficiency of dissipation of excess photon energy in the PS2 antenna was maintained in Jerba and was increased in Tabarka plants challenged with S 400 . Hence the relative salt tolerance of Jerba was associated with a better ability to use Na + and Cl -for osmotic adjustment, the absence of pigment degradation, and the concomitant PS2 protection from photodamage.

QTL Mapping of Salt Tolerance Traits with Different Effects at the Seedling Stage of Bread Wheat

“…CHL has a direct association with light harvesting potential, and researchers considered it as an important factor for photosynthetic capacity (Metwali et al 2011). Megdiche et al (2008) also reported important roles for photosynthetic pigments content considering its direct association with salt tolerance. CHL is also correlated with light harvesting capacity and acts against salt-induced oxidative damage.…”

Antioxidant defense responses: physiological plasticity in higher plants under abiotic constraints

“…In higher plants, dissipation of excess photochemical energy is an immediate and finely turned response, which occurs through heat irradiation, alternate sinks for photosynthetic elements and down regulation of photosystem II Megdiche et al 2008). The photoreduction of oxygen is an important alternative sink for the consumption of excess energy but it is associated with an increase in the generation of ROS such as H 2 O 2 , O 2 Á-, OHÁ and 1 O 2 (Foyer and Harbinson 1994;Nicolas et al 2006;Tahkokorpi et al 2007).…”

Photosynthetic Responses of Tomato Leaves to Salt and Cadmium Stresses: Growth and Chlorophyll a Fluorescence Kinetic Analyses

“…Salinity could also have a similar effect. The physiological processes affected by salinity include changes in plant growth [11], membrane permeability [12], mineral distribution [13], reduction in chlorophyll content [14][15], and decreased efficiency of photosynthesis [16][17]. Understanding the physiological mechanisms of various stress factors is critical in predicting the disturbances that influence plant growth and productivity.…”