Effects of supplementary potassium nitrate on growth and gas-exchange characteristics of salt-stressed citrus seedlings

Abstract

We investigated the effects of supplementary KNO 3 and NaCl on one-year-old, potted Valencia orange (Citrus sinensis) scions grafted on Iranian mandarin Bakraii [Citrus reticulata × Citrus limetta] (Valencia/Bakraii) and Carrizo citrange [C. sinensis × Poncirus trifoliata] (Valencia/Carrizo) rootstocks. After watering plants for 60 days with 50 mM NaCl, the lowest reduction in dry mass, stomatal conductance, and chlorophyll (Chl) content was found in Valencia/Bakraii. Bakraii accumulated more Cland Na + in roots and transferred less to Valencia leaves compared with Carrizo rootstock. Moreover, higher net photosynthetic rate was found in Valencia/Bakraii than those on Carrizo rootstock. NaCl caused a decrease in the maximal efficiency of PSII photochemistry (F v /F m ) and effective quantum yield (Φ PSII ) but elevated coefficient of nonphotochemical quenching. Salinity reduced Ca 2+ , Mg 2+ , and total N contents, and increased Na + /K + ratio in leaves and roots of both grafting combinations. Salinity increased K + and proline content in leaves and decreased K + concentrations in roots of both grafting combinations. In salinized plants, nitrate supplementation (10 mM KNO 3 ) reduced leaf abscission, Cl -, Na + , Na + /K + , and Ca 2+ concentrations in leaves and roots of both combinations. K + and N concentrations and proline increased in leaves of the nitrate-supplemented salinized plants. Supplementary nitrate increased leaf number and area, stem elongation, Chl content, F v /F m , and Φ PSII and stimulated photosynthetic activity. Thus, nitrate ameliorated the deleterious effects of NaCl stress and stimulated the plant metabolism and growth. It can be used as a vital treatment under such condition.

Research on the adaptive mechanism of photosynthetic apparatus under salt stress: New directions to increase crop yield in saline soils

“…The dissipation of excitation energy, determined as NPQ, is one of the ways that most photosynthetic mechanisms resist the adversity (Misra, Latowski, & Strzalka, ). Increased NPQ in response to NaCl treatment was observed in several plants, such as Citrus reticulata seedlings (Khoshbakht, Ghorbani, Baninasab, Naseri, & Mirzaei, ) and Morus alba (Yu et al, ). The OJIP analysis of Spirulina platensis showed that the fluorescence yield of J, I and P phases decreased sharply with the increase of salt concentration, and qP decreased when qN increased (C. Lu & Vonshak, ).…”

Effects of foliar applications of nitric oxide and spermidine on chlorophyll fluorescence, photosynthesis and antioxidant enzyme activities of citrus seedlings under salinity stress

“…Salinity stress has received increasing attention in recent years because it greatly reduces agricultural productivity (Parihar et al 2015). Salinity causes various injuries in plants, such as tissue burning, yield reduction, and finally plant death (Romero-Aranda et al 2001), causes leaf senescence, reduction PSII activities (Khayyat et al 2016), enhances membrane permeability (Dhindsa et al 1981), nutritional imbalances, and toxicity (Khoshbakht et al 2014). NaCl inhibits photosynthetic rate (PN) as a consequence of osmotic stress, which leads to a decrease in water potential and stomatal conductance (g s ), sugar accumulation, which causes feedback inhibition, and ion toxicity (e.g., an excess of Na + and Cl -) accompanied by a reduction of K + and Ca 2+ (Khoshbakht and Asgharei 2015a).…”

Effects of Salinity Sources on Growth, Physiological Process, Yield, and Fruit Quality of Grafted Rock Melon (Cucumis melo L.)

“…Al-Hamzawi (2010) has reported that the application of 15 mM KNO 3 considerably improved growth parameters by increasing plant height, leaves number, and total leaf area of cucumber. Supplementary KNO 3 under NaCl salt-stressed treatments had increased leaf number, leaf area, stem elongation, and dry matter in grafted citrus (Khoshbakht et al, 2014). Despite the positive effects mentioned in most growth parameters (Table 2), salinity induced by KNO 3 + BNS that is prolonged until the fruiting stage has resulted in a lower leaf number.…”