Monitoring of Salinity, Temperature, and Drought Stress in Grafted Watermelon Seedlings Using Chlorophyll Fluorescence

Abstract

Chlorophyll fluorescence (CF) is used to measure the physiological status of plants affected by biotic and abiotic stresses. Therefore, we aimed to identify the changes in CF parameters in grafted watermelon seedlings exposed to salt, drought, and high and low temperatures. Grafted watermelon seedlings at the true three-leaf stage were subjected to salinity levels (0, 50, 100, 150, and 200 mM) and temperature [low (8°C), moderate (24°C), and high (40°C)] stresses for 12 days under controlled environmental conditions independently. Eight CF parameters were measured at 2-day intervals using the FluorCam machine quenching protocol of the FluorCam machine. The seedlings were also exposed to drought stress for 3 days independent of salinity and temperature stress; CF parameters were measured at 1-day intervals. In addition, growth parameters, proline, and chlorophyll content were evaluated in all three experiments. The CF parameters were differentially influenced depending on the type and extent of the stress conditions. The results showed a notable effect of salinity levels on CF parameters, predominantly in maximum quantum yield (Fv/Fm), non-photochemical quenching (NPQ), the ratio of the fluorescence decrease (Rfd), and quantum yield of non-regulated energy dissipation in PSII [Y(NO)]. High temperature had significant effects on Rfd and NPQ, whereas low temperature showed significant results in most CF parameters: Fv/Fm, Y(NO), NPQ, Rfd, the efficiency of excitation capture of open photosystem II (PSII) center (Fv′/Fm′), and effective quantum yield of photochemical energy conversion in PSII [Y(PSII)]. Only NPQ and Rfd were significantly influenced by severe drought stress. Approximately, all the growth parameters were significantly influenced by the stress level. Proline content increased with an increase in stress levels in all three experiments, whereas the chlorophyll (a and b) content either decreased or increased depending upon the stressor. The results provided here may be useful for understanding the effect of abiotic stresses on CF parameters and the selection of index CF parameters to detect abiotic stresses in grafted watermelon seedlings.

Species-specific responses of Antarctic terrestrial microalgae to salinity stress. Comparative study in Klebsormidium sp. and Stigeoclonium sp.

“…The observed decrease in F M and F M ´ found at 3 M NaCl in Klebsormidium and Stigeoclonium is a well-known phenomenon found in previous salinity studies in cyanobacteria (Lu and Vonshak 2002), microalgae (Liang et al 2014) and vascular plants (e.g., Hniličková et al 2017, Oláh et al 2021. Rfd, which is considered an indicator of plant vitality under stressful con-ditions, decreased at the highest salinity level (3M NaCl) as well, in accordance with Shin et al (2020Shin et al ( , 2021, who also found a significant decrease in Rfd levels in plants exposed to the extreme salinity stress.…”

Effects of low temperature on flowering and the expression of related genes in Loropetalum chinense var. rubrum

“…This was repeated until the flower bud differentiation was completed in the low temperature environment. In the low temperature environment, the trend of NPQ is consistent with Rfd (Shin et al, 2021), therefore, the NPQ curve of L. chinense var. rubrum under low temperature treatment has a similar trend to the Rfd curve.…”

Effects of NaCl on Growth, Chlorophyll and Sugar Contents in Rice (Oryza sativa L.) Malidum and Malidang Cultivars

“…The efficiency of photosynthesis in the plant is reduced. Salinity decreased the chlorophyll content [19][20][21][22] . Salt reduces the resistance of the mesophyll 23 .…”