Effect of Saline–Alkali Stress on Sugar Metabolism of Jujube Fruit

Abstract

Sugar, an osmoregulatory substance used by plants to adapt to abiotic stresses such as drought and salinity, is one of the most important indexes of fruit quality. In this study, 0–150 mM saline–alkali solutions (NaCl:NaHCO3 = 3:1) were used to irrigate the roots of 10-year-old “Junzao” fruit trees during the growth period to explore the regulation mechanism of different concentrations of saline–alkali stress on sugar and reactive oxygen metabolism in jujube fruit at maturity. The results showed that under low stress (0~90 mM), the contents of sucrose, glucose, and fructose in the jujube fruit and the activities of sucrose phosphate synthase (SPS), sucrose synthase decomposition direction (SS-I), and sucrose synthase synthesis direction (SS-II) increased with increases in stress concentration, results that were consistent with the relative expression trends of the SPS and SS genes; however, the results were reversed under high concentrations (120 and 150 mM). The soluble acid invertase (S-AI) activity decreased with increases in stress concentration under low stress, and the results were reversed with high stress, which was consistent with the relative expression trends of the ZjcINV3, ZjnINV1, and ZjnINV3. Research regarding the response of antioxidant enzymes in fruits under saline–alkali stress showed that only the differences in peroxidase (POD) activity under saline–alkali stress were consistent with sugar accumulation; the proline (PRO), catalase (CAT) decreased and the malondialdehyde (MDA) superoxide dismutase (SOD) increased with increases in saline–alkali stress. These results indicate that the sugar metabolism and antioxidase jointly promote and regulate sugar accumulation in jujube fruits in a low saline–alkali environment.

A comparative plastomic analysis ofZiziphus jujubavar.spinosa(Bunge) Hu ex H. F. Chow and implication of the origin of Chinese jujube

“…This was hypothesized to be one of the molecular foundations contributing to the adaption of Polypodiaceae to the environment. Stress tolerance of sour jujube to various environmental conditions was relatively strong compared to Chinese jujube ( Wang et al . 2018 ), and the potential contribution of plastome composition to high stress tolerance needs to be clarified.…”

“…2015 ). It has significant ecological value and is typically used for soil and water conservation ( Wang et al . 2018 ).…”

Physiological and Transcriptomic Analyses Reveal the Effects of Elevated Root-Zone CO2 on the Metabolism of Sugars and Starch in the Roots of Oriental Melon Seedlings

“…Sugars indirectly regulate carbohydrate metabolism under abiotic stress, which contributes to plant growth and development [ 34 , 35 , 36 ]. Several environmental factors, including drought, cold, and salinity, have been shown to alter carbohydrate metabolism [ 37 , 38 , 39 ]. The results of this study demonstrated that alterations in the contents of soluble sugars and starch in the roots are attributed to the adaptation of the basic physiological indices of roots at different root-zone CO 2 concentrations ( Figure 5 ).…”

Underlying Mechanisms of Action to Improve Plant Growth and Fruit Quality in Crops under Alkaline Stress

“…Another osmoregulation alternative can be the increase in sugar concentration, in this regard it is mentioned that in fruits of Jujube "Junzao" irrigated with a moderate alkaline solution (90 mM of NaCl:NaHCO 3 (3:1)), an increase in sucrose, glucose, and fructose content was observed, in addition to an increase in sucrose phosphate synthase (SPS) and sucrose synthase (SS-I) activities [53] allowing a partial attenuation of stress and maintaining plant and fruit quality. In addition to the accumulation of soluble sugars [14], proline is associated with osmoregulatory mechanisms in plants under alkaline conditions [46].…”

“…Similarly, reduction of the photosynthetic process by carbonate salts minimizes the synthesis of some pigments, such as anthocyanins, which may affect the quality of leaves, flowers, and fruits [9,52]. In addition, the aforementioned soluble sugars participate in carbon stores and are critical for osmoregulation, osmotic adjustment, and ROS scavenging [14,53].…”