Abstract
High-temperature stress is a major risk to fresh-market Salvia production, and heat intolerance is a major constraint in sage cultivation, particularly during the hot summer season. Previously, we investigated heat tolerance in five common-market cultivars of sage plants using leaf relative injury (RI) values and found that S. elegans Vahl (SE) and S. officinalis L. (SO) were the most and least heat-tolerant species, respectively. The exogenous applications of salicylic acid (SA) and calcium chloride (CaCl2) to alleviate heat stress in various species have been extensively studied, but reports of the effects of SA and CaCl2 treatments on the heat tolerance of sage plants are scarce. The objective of this study was to investigate how SA and CaCl2 affect the physiology and morphology of SE and SO plants under high-temperature conditions. Potted plants were pretreated with SA (0, 100, 200, 400, and 800 μM) and CaCl2 (0, 5, 10, and 15 mM), alone and combined, exposed to 55 °C and 80% humidity for 30 min, then placed in an environment-controlled chamber at 30 °C for three days and evaluated for changes in phenotypic appearance, RI, spectral reflectance, and chlorophyll fluorescence indices at different time intervals. Plants watered without chemical solutions were used as controls. Our results show that the growth of SO plants pretreated with SA and CaCl2 was more robust, compared with control plants, which were considerably affected by heat stress, resulting in brown, withered leaves and defoliation. The effects of the combined applications of SA (100 μM) and CaCl2 (5 mM) to SO plants were superior to control plants in increasing values of soil-plant analysis development (SPAD), normalized difference vegetation index (NDVI), and the maximal quantum yield of photosystemII photochemistry (Fv/Fm), while reducing RI%. Furthermore, SO plants exhibited higher SPAD and Fv/Fm values and lower RI% than SE plants in combined treatments at all time intervals after heat stress, implying that different genotypes displayed variations in their SPAD, Fv/Fm, and RI%. Thus, a combined treatment of 100 μM of SA and 5 mM of CaCl2 is effective and beneficial to plant appearance and ability to ameliorate heat stress. These indices can be used as indicators to characterize the physiology of these plants and applied on a commercial scale for informing the development of rapid and precise management practices on bedded sage plants grown in plant factories to achieve maximum market benefit.
Highlights
Salvia is a member of the Lamiaceae, a family represented by 45 genera
No significant differences in normalized difference vegetation index (NDVI) levels were observed in S. officinalis L. (SO) plants treated with salicylic acid (SA) at all heat-stress time durations, except for the 3d period after heat stress, in which SO plants treated by 100~400 μM of SA exhibited significantly higher
The influence of SA and CaCl2 treatments applied alone and in combination on sage plants was assessed by observing changes in the physiology and morphology of plants exposed to 30 ◦ C for 3d
Summary
Salvia is a member of the Lamiaceae, a family represented by 45 genera. Its fragrant plants are used in folk medicines around the world, and many of its species are important in the pharmacology, perfume, cosmetics, and food industries because they contain volatile and aromatic oils [1,2]. L. (SO) have specific spasmolytic, astringent, antimicrobial, antihidrotic, antioxidant, and hepatoprotective effects, in addition to sensory, antigenotoxic, and chemopreventive activity [4,5,6] There is considerable pressure on the floriculture industry to produce ornamental plants more efficiently, and as the landscaping demand for sage plants is increasing, any method to improve heat tolerance in the hot summer season is important to Taiwan nurserymen. The responses of Salvia species to water stresses [7,8], salt stresses [9,10], and ozone-induced oxidative stresses [11] are reported, but there is limited information available regarding the morphology and physiology of sage plants grown under high-temperature stress
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
