Hassan Nemat, Ebeed Heba, Aljaarany Alshafei
1Botany and Microbiology Department, Faculty of Science, Damietta University, Damietta, Egypt.
2Faculty of Science, Sabha University, Sabha, Libya.
Physiol Mol Biol Plants. 2020 Feb;26(2):233-245. doi: 10.1007/s12298-019-00744-7. Epub 2020 Jan 2.
Polyamines (PAs) are positively charged molecules known to mitigate drought stress; however, little is known about their mechanism of alleviating drought stress. We investigated the effects of PAs exogenously applied as a seed primer and as a foliar spray on the growth, membrane stability (MS), electrolyte leakage (EL), Na and K cations, reactive oxygen species (ROS), catalase (CAT; EC 1.11.1.6) and guaiacol peroxidase (GPX; EC 1.11.1.7) activity and chloroplast ultra-structure in wheat ( L.; cv. Sakha-94) under drought stress. Three PA solutions, namely, putrescine, spermine and a mixture of the two (Mix), were each applied at a concentration of 100 µM. Our study demonstrated that the retardation of chlorophyll loss and elevation of Rubisco levels were involved in PA-enhanced growth under drought stress. These relationships were mainly reflected in elevated fresh weight and dry weight in response to foliar spraying with all PA solutions and seed priming with the Mix solution. The elevated growth seemed to be due to increased photosynthetic pigments, protein and Rubisco. In contrast, drought decreased growth, photosynthetic pigments, protein and Rubisco. MS was enhanced by PAs applied as a seed primer or foliar spray, as shown by clear reductions in EL %, malondialdehyde (MDA) content and the Na/K ratio as well as reduced ROS markers and elevated CAT (but not GPX) activity. Further study showed that the Mix solution of PAs, applied either during seed priming or as a foliar spray, improved chloroplast ultra-structure, suggesting that improvements in Rubisco and photosynthetic pigments were involved in PA maintenance of chloroplast stability. Therefore, the present study showed that elevated CAT activity is the main mechanism through which PAs reduce ROS and MDA, thereby improving MS and protecting mesophyll cells structurally and functionally under drought stress in wheat.
多胺（PAs）是已知可减轻干旱胁迫的带正电荷分子；然而，关于它们缓解干旱胁迫的机制知之甚少。我们研究了作为种子引发剂和叶面喷雾剂外源施用的多胺对干旱胁迫下小麦（L.；品种Sakha - 94）的生长、膜稳定性（MS）、电解质渗漏（EL）、钠和钾阳离子、活性氧（ROS）、过氧化氢酶（CAT；EC 1.11.1.6）和愈创木酚过氧化物酶（GPX；EC 1.11.1.7）活性以及叶绿体超微结构的影响。三种多胺溶液，即腐胺、亚精胺和两者的混合物（Mix），均以100 μM的浓度施用。我们的研究表明，叶绿素损失的延缓和核酮糖-1,5-二磷酸羧化酶（Rubisco）水平的升高参与了干旱胁迫下多胺促进的生长。这些关系主要体现在用所有多胺溶液进行叶面喷施以及用Mix溶液进行种子引发后鲜重和干重的增加上。生长的增加似乎是由于光合色素、蛋白质和Rubisco的增加。相比之下，干旱会降低生长、光合色素、蛋白质和Rubisco。作为种子引发剂或叶面喷雾剂施用的多胺增强了膜稳定性，表现为EL%、丙二醛（MDA）含量和钠/钾比明显降低，以及ROS标志物减少和CAT（但不是GPX）活性升高。进一步的研究表明，无论是在种子引发期间还是作为叶面喷雾剂施用的多胺Mix溶液，都改善了叶绿体超微结构，这表明Rubisco和光合色素的改善参与了多胺维持叶绿体稳定性的过程。因此，本研究表明，CAT活性的升高是多胺减少ROS和MDA的主要机制，从而在干旱胁迫下改善小麦的膜稳定性，并在结构和功能上保护叶肉细胞。
