Silicon nutrition counteracts salt-induced damage associated with changes in biochemical responses in apple

ABSTRACT Salt stress is an environmental challenge that adversely influences plant responses. Silicon (Si) nutrition plays critical roles in plant tolerance to salt stress. Apple (Malus domestica Borkh.), a salt sensitive fruit species, was used in the present experiment to investigate the influences of Si on salt stress as well as on alterations of biochemical responses. Apple cv Fuji grafted on M9 clonal rootstock was exposed to salt stress for 4 months with 35 mmol·L-1 NaCl. CaSiO3 doses (0.5, 1 and 2 mmol·L-1) were applied to the roots of the salt-stressed apple plants except control. Si application resulted in mitigation of salt stress in apple plants. The highest chlorophyll a, b and a + b were obtained from the 1 mmol·L-1 Si treatment (5.37, 2.41 and 7.78 μg·g-1 fw, respectively). Moreover, Si treatment had higher chlorophyll content compared to the control as well as salt exposed plants. Silicon applications led to a reduction in malondialdehyde (MDA) content even lower than control. The 0.5 mmol·L-1 Si treatment had the highest values of ascorbate peroxidase (APX) and phenolic content. The results show that Si nutrition plays important roles in apple salt tolerance via biochemical mechanisms and that it can be used in areas subject to salt stress for apple growing.摘要 盐胁迫是对植物生长发育产生不利影响的环境胁迫因子。硅（Si）营养在植物耐盐性调控中发挥关键作用。本实验以盐敏感果树物种苹果（Malus domestica Borkh.）为试材，探究硅对盐胁迫及植物生化响应变化的影响。实验选用嫁接于M9无性系砧木的富士苹果品种，采用35 mmol·L⁻¹氯化钠进行为期4个月的盐胁迫处理；除对照组外，向盐胁迫苹果植株的根部施加浓度分别为0.5、1和2 mmol·L⁻¹的硅酸钙（CaSiO3）。结果表明，施加硅可缓解苹果植株的盐胁迫伤害：1 mmol·L⁻¹硅处理组的叶绿素a、叶绿素b及总叶绿素（a+b）含量最高，分别为5.37、2.41和7.78 μg·g⁻¹鲜重；且硅处理组的叶绿素含量均高于对照组与单纯盐胁迫组。此外，施加硅可降低丙二醛（MDA）含量，甚至低于对照组；0.5 mmol·L⁻¹硅处理组的抗坏血酸过氧化物酶（APX）活性与酚类物质含量最高。本研究结果证实，硅营养可通过生化调控机制提升苹果的耐盐性，可应用于盐胁迫区域的苹果种植。