Effects of sodium chloride stress on gas exchange, chlorophyll content and nutrient concentrations of nine citrus rootstocks

Abstract

We investigated the influence of salinity (0, 25, 50, or 75 mM NaCl) on gas exchange and physiological characteristics of nine citrus rootstocks (Cleopatra mandarin, Carrizo citrange, Macrophylla, Iranian mandarin Bakraii, Rangpur lime, Rough lemon, Sour orange, Swingle citrumelo, and Trifoliate orange) in a greenhouse experiment. Total plant dry mass, total chlorophyll (Chl) content, and gas-exchange variables, such as net photosynthetic rate (P N ), stomatal conductance (g s ), intercellular CO 2 concentration, were negatively affected by salinity. In addition, ion concentrations of Cland Na + increased by salinity treatments. Salinity also increased Mg 2+ content in roots and reduced Ca 2+ and Mg 2+ concentrations in leaves. The K + concentration in leaves was enhanced at low salinity (25 mM NaCl), whereas it decreased with increasing salinity stress. Salinity caused a decline in K + contents in roots. The rootstocks showed major differences in the extent of Cland Na + accumulation in leaves and in their ability to maintain the internal concentrations of essential nutrients in response to different salinity. Therefore, in addition to inhibitory effects of high concentrations of Cland Na + , an imbalance of essential nutrients may also contribute to the reduction in gas exchange under saline conditions. Higher tolerance of rootstocks to salinity could be associated with the reduction of Cland Na + uptake and transport to leaves, ability to keep higher Chl, g s , P N , and better maintenance of nutrient uptake even under high salinity. We found that Sour orange and Cleopatra mandarin were the rootstocks most tolerant to salinity of all nine studied. In addition, Trifoliate orange, Carrizo citrange, and Swingle citrumelo were the rootstocks most sensitive to salt stress followed by the Rough lemon and Macrophylla that showed a low-to-moderate tolerance, and Rangpur lime and Bakraii, with a moderate-to-high tolerance to high salinity.

Fine root growth and water use efficiency in alfalfa (Medicago sativaL. cv. Gongong No. 1) planted along a salinity gradient in coastal area of Dalian, Northeast China

“…P N decline is a general response of plants to salinity stress mostly due to membrane damage and stomatal closure (Marín-Guirao et al 2011;Ge et al 2014;Khoshbakht et al 2015). In our study, potted alfalfa in the controlling experiment showed declining P N with an increase of salinity level.…”

“…Additionally, this trend not only occurred during the response of fine root morphology to saline gradient described above, but also implied a key mechanism for depressed photosynthetic inland-alfalfa performance in the future. With the increase of salinity stress, T r decline is a common response of juvenile plants among a wide range of species, such as Phoenix dactylifera L. (Youssef and Awas 2008), citrus (Khoshbakht et al 2015), Sarcocornia fruticosa (L.) A.J. Scott (Redondo-Gómez et al 2006), and Arundo donax L. (Nackley and Kim 2015).…”

Rootstock Breeding for Abiotic Stress Tolerance in Citrus

“…Khoshbakht et al [41] reported that the effects of salinity on photosynthesis range from the restriction of CO 2 diffusion into the chloroplast, via limitations on stomatal opening mediated by shoot-and root-generated hormones, and on the mesophyll transport of CO 2 , to alterations in leaf photochemistry and carbon metabolism. The authors conducted a study and investigated the NaCl effects on gas exchange parameters of nine citrus rootstocks and reported that sour orange and Cleopatra mandarin were the rootstocks most tolerant to salinity of all the nine citrus rootstocks studied.…”

Evaluation of salt tolerance in Eruca sativa accessions based on morpho-physiological traits

“…It is generally believed that salt stress causes a decrease in chlorophyl content (Khoshbakht, Ramin & Baninasab, 2015;Qiu et al, 2017). Some reports have, however, shown an increase in chlorophyl content for a few plant species under salt stress (Stefanov et al, 2016;Shah, Houborg & McCabe, 2017).…”