Change of Physiological Properties and Ion Distribution by Synergistic Effect of Ca2+ and Grafting under Salt Stress on Cucumber Seedlings

Abstract

Salinization is an important soil environmental problem, which severely restricts the sustainable production of cucumbers. Therefore, how to improve the salt tolerance of cucumbers is a global problem. Grafting improves the resistance of crops, and calcium ion (Ca2+) weakens the permeability of the plasma membrane. In this paper, grafting cucumber with NaCl-free treatment was the control treatment (CK). Under salt stress, grafting combined different concentrations of CaCl2 and non-grafted (NG) were considered as treatments. The synergistic effect of grafting and Ca2+ to relieve salt stress on cucumber seedlings was investigated. The results revealed that grafting (G), Ca2+, and their interaction significantly influenced plant growth, osmotic adjustment substances, enzyme activities, and iron distribution. Under salt stress, grafting increased the absorption of potassium ion (K+) and Ca2+ in cucumber stems and leaves, but compared with NG, it significantly reduced the accumulation of Na+ in those parts by 61.58–89.40%. Moreover, supplication suitable Ca2+ content had a similar effect. Supplemental Ca2+ promoted the shoot and root biomass. The 10 mM L−1 Ca2+ had the highest biomass, compared with CK and NG, an increase of 49.95% and 20.47%, respectively; the lowest sodium ion (Na+). The highest Ca2+ accumulation in cucumber stem and leaves was found in 10 mM L−1 Ca2+ treatment. Supplemental Ca2+ increased free proline (Pro) and decreased malondialdehyde (MDA) content during the entire salt stress period. At 11 days, compared with 0 mM L−1 Ca2+ treatment, pro content was increased by 4.70–25.31, and MDA content was decreased by 1.08–4.90 times, respectively. Superoxide dismutase (SOD) activity, relative growth rate of plant height (PH), and stem volume (SV), and K+/Na+ and K+/Ca2+ in cucumber leaves had significantly negative correlations with a salt damage score. The combination of grafting and supplemental 5–20 mM L−1 Ca2+ relieved salt damage to cucumber seedlings. The best synergistic effect was obtained with grafting and 10 mM L−1 Ca2+ treatment.

Cucumber grafting on indigenous cucurbit landraces confers salt tolerance and improves fruit yield by enhancing morpho-physio-biochemical and ionic attributes

“…Grafting (an eco-friendly surgical horticulture technique) of cucumber on suitable rootstock improves the crop growth and productivity by increasing the morphological (root tip, diameters, and length), physiological (photosynthetic rate, water use efficiency) and biochemical (SOD, CAT and POX) indices 21 , 22 . Grafting helps crop plants to tolerate salt stress by replacing the sensitive crop roots with tolerant genotypes species, and decreasing the production losses 23 via reducing the Na + and enhancing the K + uptake through the leaves and stems. Thus, maintains appropriate K + : Na + .…”

The Most Suitable Calcium Concentration for Growth Varies among Different Tree Species—Taking Pinus tabuliformis, Pinus sylvestris var. mongolica, Populus, and Morus alba as Examples

“…Ca 2+ is an important nutrient and a signaling molecule that regulates plant growth and development [28]. Previous studies have demonstrated that treatment with 10 mmol•L −1 CaCl 2 significantly increases the biomass of Zoysia japonica and cucumber [29,30]. Moreover, the foliar application of Ca 2+ promotes peanut growth and improves the quality of sweet cherries [31][32][33].…”

Optimal exogenous calcium alleviates the damage of Snow-melting agent to Salix matsudana seedlings

“…Tuna et al (2007) found that the application of exogenous calcium improved the inhibition of plant growth by salt stress. The addition of calcium has been shown effective in promoting the growth and yield of tomato, soybean and cucumber under salt stress (Navarro et al, 2000;Elkelish et al, 2019;Wang et al, 2021). The leaf area, biomass and roots of salt-tolerant and saltsensitive rice have been shown to increase significantly with increasing exogenous calcium (Cha-um et al, 2012).…”