Taj Zarin, Challabathula Dinakar
Department of Life Sciences, School of Life Sciences, Central University of Tamil Nadu, Thiruvarur, India.
Front Microbiol. 2021 Jan 8;11:547750. doi: 10.3389/fmicb.2020.547750. eCollection 2020.
Tomato () and rice () are the two most important agricultural crops whose productivity is severely impacted by salinity stress. Soil salinity causes an irreversible damage to the photosynthetic apparatus in plants at all developmental stages leading to significant reduction in agricultural productivity. Reduction in photosynthesis is the primary response that is observed in all glycophytic plants during salt stress. Employment of salt-tolerant plant growth-promoting bacteria (PGPB) is an economical and viable approach for the remediation of saline soils and improvement of plant growth. The current study is aimed towards investigating the growth patterns and photosynthetic responses of rice and tomato plants upon inoculation with halotolerant PGPB ET101 under salt stress conditions. Tomato and rice plants inoculated with PGPB showed increased growth rate and stimulated root growth, along with higher transpiration rates (), stomatal conductance ( ), and intracellular CO accumulation (Ci). Additionally, correlation of relative water content (RWC) to electrolyte leakage (EL) in tomato and rice plants showed decreased EL in inoculated plants during salt stress conditions, along with higher proline and glycine betaine content. Energy dissipation by non-photochemical quenching (NPQ) and increased photorespiration of 179.47% in tomato and 264.14% in rice plants were observed in uninoculated plants subjected to salinity stress. Furthermore, reduced photorespiration with improved salinity tolerance is observed in inoculated plants. The higher rates of photosynthesis in inoculated plants during salt stress were accompanied by increased quantum efficiency (ΦPSII) and maximum quantum yield ( / ) of photosystem II. Furthermore, inoculated plants showed increased carboxylation efficiency of RuBisCO, along with higher photosynthetic electron transport rate (ETR) () during salinity stress. Although the total cellular ATP levels are drastically affected by salt stress in tomato and rice plants along with increased reactive oxygen species (ROS) accumulation, the restoration of cellular ATP levels in leaves of inoculated plants along with decreased ROS accumulation suggests the protective role of PGPB. Our results reveal the beneficial role of ET101 in protection of photosynthesis and amelioration of salinity stress responses in rice and tomato plants.
番茄（ ）和水稻（ ）是两种最重要的农作物，其生产力受到盐胁迫的严重影响。土壤盐度对植物在所有发育阶段的光合器官造成不可逆转的损害，导致农业生产力显著下降。光合作用的降低是所有盐敏感植物在盐胁迫期间观察到的主要反应。使用耐盐植物促生细菌（PGPB）是修复盐渍土壤和促进植物生长的一种经济可行的方法。当前的研究旨在调查在盐胁迫条件下接种耐盐PGPB ET101后水稻和番茄植株的生长模式及光合响应。接种PGPB的番茄和水稻植株显示出生长速率增加、根系生长受到刺激，同时蒸腾速率（ ）、气孔导度（ ）和细胞内CO积累（Ci）更高。此外，番茄和水稻植株中相对含水量（RWC）与电解质渗漏（EL）的相关性表明，在盐胁迫条件下接种植株的EL降低，同时脯氨酸和甘氨酸甜菜碱含量更高。在遭受盐胁迫的未接种植株中，观察到通过非光化学猝灭（NPQ）耗散能量，番茄植株的光呼吸增加了179.47%，水稻植株增加了264.14%。此外，在接种植株中观察到光呼吸降低且耐盐性提高。盐胁迫期间接种植株较高的光合速率伴随着光合系统II的量子效率（ΦPSII）和最大量子产量（ / ）增加。此外，接种植株在盐胁迫期间显示出RuBisCO羧化效率提高，同时光合电子传递速率（ETR）（ ）更高。尽管盐胁迫对番茄和水稻植株的总细胞ATP水平有显著影响，同时活性氧（ROS）积累增加，但接种植株叶片中细胞ATP水平的恢复以及ROS积累的减少表明了PGPB的保护作用。我们的结果揭示了ET101在保护水稻和番茄植株光合作用及改善盐胁迫响应方面的有益作用。
