Saline-alkali stress is one of the main abiotic stress factors affecting plant growth and development. Trollius chinensis is a perennial herbal medicinal plant with high values for garden application. However, its response and tolerance to saline-alkali stress is unclear. In this study, we mixed four salts (NaCl: Na2SO4: NaHCO3: Na2CO3) with a concentration ratio of 1:9:9:1, and applied low (40 and 80 mM) and high (120 and 160 mM) saline-alkali stress to analyze osmotic regulation substances, antioxidant systems and the gene expression of T. chinensis. Along with higher saline-alkali stress, the leaf relative water content (RWC) started to decrease only from high stress, while the malondialdehyde (MDA) content in leaves decreased continuously, and the contents of proline (Pro), soluble sugar (SS) and soluble protein (SP) increased compared with control. The activities of antioxidant enzymes and the contents of non-enzymatic antioxidants were increased positively with the accumulation of superoxide anion (O2•–) and hydrogen peroxide (H2O2). For instance, the ascorbic acid-glutathione (AsA-GSH) cycle was enhanced in T. chinensis seedling leaves subject to saline-alkali stress. Principal Component Analysis (PCA) indicates that MDA, Pro, SS, SP, H2O2, O2•–, and GSH are important indexes to evaluate the response and tolerance of T. chinensis to saline-alkali stress. Through RNA-Seq, a total of 474 differentially expressed genes (DEGs) were found in plant under low saline-alkaline stress (40 mM, MSA1) vs. control. Among them, 364 genes were up-regulated and 110 genes were down-regulated. DEGs were extensively enriched in carbohydrate transport, transferase activity, zeatin biosynthesis, ABC transporters, and spliceosome. The transcription factor family MYB, BZIP, WRKY, and NAC were related to its saline-alkali tolerance. In addition, some DEGs encode key enzymes in the processes of osmoregulation and antioxidation, including betaine aldehyde dehydrogenase (BADH), inositol monophosphatase (IMP), chloroperoxidase (CPO), thioredoxin (Trx), and germin-like protein (GLPs) were found. Overall, these findings provide new insights into the physiological changes and molecular mechanism of T. chinensis to saline-alkali stress and lay a foundation for application of T. chinensis in saline-alkali environment.
Senescence is the main limitation for cut foliage display in vase. Naturally occurring polyamines such as putrescine (Put) have been considered effective anti-senescence agents. However, effect of Put on cut foliage in vase in a realistic indoor environment has not yet been revealed. In the present study, effects of Put spraying on the postharvest performance of cut foliage of Nephrolepis cordifolia L. were investigated. Cut fronds sprayed with deionized water (Put0) showed visible injuries after 10 days in vase. Meanwhile, chlorophyll (Chl), soluble protein (Sp), and proline (Pro) content were decreased by 60.15, 57.93, and 73.09% respectively, photochemical activity reflected by Chl fluorescence parameters was inhibited, whereas electrolyte leakage (EL), contents of soluble sugar (Ss), malondialdehyde (MDA), and hydrogen peroxide (H 2 O 2) were increased (+194.29, +44.83, +34.06, and +178.01%, respectively). Put spraying extended the vase life of the cut foliage and the 2.0 mM Put had a longer vase life (21 days) than 0.2 mM (15 days). Leaf spraying of 2.0 mM Put for 10 days significantly ameliorated the losses of Chl, Sp, and Pro content (−10.72, −26.29, and −42.64%, respectively), followed by 0.2 mM Put (−27.36, −36.24, and −60.55%, respectively). Put spraying also improved photochemical capability and prevented membrane impairment as well as visible injury in comparison with Put0. In addition, 2.0 mM Put had a better mitigating ability than that of 0.2 mM. Leaf spraying of 2.0 mM Put greatly reduced the decline of the effective quantum yield of photochemical energy conversion in PSII (FPSII), the maximal quantum yield of PSII photochemistry measured in the dark-adapted state (Fv/Fm) and electron transport rate (ETR) (−7.89, −12.91, and −10.06%, respectively), and also inhibited the increases of EL, MDA, Ss, and H 2 O 2 (+31.87, +6.43, +16.22, and +49.40%, respectively). Overall, Put played important roles in deterring the degradation of Chl, Ss, and Pro, detoxifying the H 2 O 2 , weakening the sugar signaling, mitigating the decline of photochemical activity, and eventually postponing the leaf senescence. The present study gives new insights into effects of Put on leaf senescence and provides a strategy for preserving post-harvest cut foliage.
Methyl jasmonate (MeJA) induces various defense responses in seed plants, but for early plant lineages, information on the potential of jasmonates to elicit stress signaling and trigger physiological modifications is limited. The spikemoss Selaginella martensii was exposed to a range of MeJA concentrations (0, 10, 25, and 50 mM), and biogenic volatile organic compound (BVOC) emissions, photosynthetic rate (A) and stomatal conductance (gs) were continuously measured. In addition, changes in phytohormone concentrations and gene expression were studied. Enhancement of methanol, lipoxygenase pathway volatiles and linalool emissions, and reductions in A and gs, were MeJA dose-dependent. Before MeJA treatment, the concentration of 12-oxo-phytodienoic acid (OPDA) was seven-fold higher than Jasmonic acid (JA). MeJA treatment rapidly increased (within 30 minutes) OPDA and JA concentrations, with the latter more responsive. Some genes involved in BVOC biosynthesis and OPDA-specific response were upregulated at 0.5 h after MeJA spraying, while those in JA signaling pathway were not affected. Although JA was synthesized in S. martensii, OPDA was prioritized as a signaling molecule upon MeJA application. MeJA inhibited primary and enhanced secondary metabolism; we propose that the fast-emitted linalool could serve as a marker of elicitation of stress-induced metabolism in lycophytes.
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