Role of Spermidine in Photosynthesis and Polyamine Metabolism in Lettuce Seedlings under High-Temperature Stress

Abstract

High temperature is a huge threat to lettuce production in the world, and spermidine (Spd) has been shown to improve heat tolerance in lettuce, but the action mechanism of Spd and the role of polyamine metabolism are still unclear. The effects of Spd and D-arginine (D-arg) on hydroponic lettuce seedlings under high-temperature stress by foliar spraying of Spd and D-arg were investigated. The results showed that high-temperature stress significantly inhibited the growth of lettuce seedlings, with a 33% decrease in total fresh weight and total dry weight; photosynthesis of lettuce seedlings was inhibited by high-temperature stress, and the inhibition was greater in the D-arg treatment, while the Spd recovery treatment increased net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), stomatal limit value (Ls), and intercellular CO2 concentration (Ci). High-temperature stress significantly reduced the maximum photochemical efficiency (Fv/Fm), photochemical quenching coefficient (qP), electron transport rate (ETR), and photochemical efficiency of PSII (ΦPSII), increased the non-photochemical burst coefficient (NPQ) and reduced the use of light energy, which was alleviated by exogenous Spd. The increase in polyamine content may be due to an increase in polyamine synthase activity and a decrease in polyamine oxidase activity, as evidenced by changes in the expression levels of genes related to polyamine synthesis and metabolism enzymes. This evidence suggested that D-arg suppressed endogenous polyamine levels in lettuce and reduced its tolerance, whereas exogenous Spd promoted the synthesis and accumulation of polyamines in lettuce and increased its photosynthetic and oxidative stress levels, which had an impact on the tolerance of lettuce seedlings.

Supplementation of nitric oxide and spermidine alleviates the nickel stress-induced damage to growth, chlorophyll metabolism, and photosynthesis by upregulating ascorbate–glutathione and glyoxalase cycle functioning in tomato

“…(2016) . Recently, in heat-stressed lettuce, He et al. (2022) have also observed significant alleviation in the parameters P n , C i , g s , E , F v / F m , qP, and ETR with Spd application, which resulted in improved growth, water use efficiency, and biomass production.…”

“…Recently, in heat-stressed lettuce, He et al (2022) have also observed significant alleviation in the parameters P n , C i , g s , E, F v / F m , qP, and ETR with Spd application, which resulted in improved growth, water use efficiency, and biomass p r od u c t i o n . I m p r o v e d c hl o r o p h y l l s y n t h e s i s a n d photosynthesis in NO-and Spd-treated plants can directly influence the carbon metabolism and the carbon-nitrogen balance (Du et al, 2016;Farag et al, 2017), which will otherwise be drastically affected by Ni stress (Sheoran et al, 1990).…”

Physiological, Metabolic, and Transcriptomic Analyses Reveal Mechanisms of Proliferation and Somatic Embryogenesis of Litchi (Litchi chinensis Sonn.) Embryogenic Callus Promoted by D-Arginine Treatment

“…In cotton, exogenous D-Arg can significantly reduce endogenous Put levels, thereby lowering PAs level [11]. In lettuce, the application of D-Arg can reduce endogenous PAs level and reduce the tolerance of lettuce seedlings to high temperatures [12].…”

Quantifying Chilling Injury on the Photosynthesis System of Strawberries: Insights from Photosynthetic Fluorescence Characteristics and Hyperspectral Inversion

“…Parameters of photosynthesis (A, g s , E, etc.) [13,14], dynamics of chlorophyll fluorescence (F v /F m , Y(II), qP, etc.) [15,16], and solarinduced chlorophyll fluorescence (SIF) [17,18] are considered valuable indicators to reveal the physiological regulatory effects of the photosynthetic system under temperature stress.…”