Responses of photosynthetic characteristics of oat flag leaf and spike to drought stress

Drought is one of the main environmental stress factors affecting plant growth and yield. The impact of different PEG concentrations on the photosynthetic performance of maize (Zea mays L. Mayflower) and sorghum (Sorghum bicolor L. Foehn) was investigated. The activity of the photosynthetic apparatus was assessed using chlorophyll fluorescence (PAM and JIP test) and photooxidation of P700. The data revealed that water deficiency decreased the photochemical quenching (qP), the ratio of photochemical to nonphotochemical processes (Fv/Fo), the effective quantum yield of the photochemical energy conversion in PSII (ΦPSII), the rate of the electron transport (ETR), and the performance indexes PItotal and PIABS, as the impact was stronger in sorghum than in maize and depended on drought level. The PSI photochemistry (P700 photooxidation) in sorghum was inhibited after the application of all studied drought levels, while in maize, it was registered only after treatment with higher PEG concentrations (30% and 40%). Enhanced regulated energy losses (ΦNPQ) and activation of the state transition under drought were also observed in maize, while in sorghum, an increase mainly in nonregulated energy losses (ΦNO). A decrease in pigment content and relative water content and an increase in membrane damage were also registered after PEG treatment. The experimental results showed better drought tolerance of maize than sorghum. This study provides new information about the role of regulated energy losses and state transition for the protection of the photosynthetic apparatus under drought and might be a practical approach to the determination of the drought tolerance of plants.

Section: Introductionmentioning

confidence: 95%

Sensitivity of the Photosynthetic Apparatus in Maize and Sorghum under Different Drought Levels

Stefanov

Rashkov

Borisova

et al. 2023

“…Drought-tolerant plants have less reduction in water content, higher membrane stability, and photosynthetic activity. RWC is a measure of plant water status, reflecting the metabolic activity in tissues and plants’ capacity for osmotic adjustment [ 51 ], and is used as an index for dehydration tolerance [ 20 , 25 , 52 ]. Its stronger reduction in Fermer plants under moderate stress indicates lower drought tolerance in comparison to Gizda ( Figure 1 a).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, carotenoids in higher plants have many roles, including the regulation of light harvesting [ 54 ], ROS-scavenging, and preventing oxidative damage, thereby increasing plant stress tolerance [ 55 ]. The decline in the abundance of photosynthetic pigments could have a negative impact on the effective photosynthetic performance and crop yield [ 51 , 56 ]. A higher Chl and Car content under stress conditions has also been associated with the tolerance of plants, as the decrease in pigment content correlates with decreased RWC [ 20 ], which was demonstrated by our results indicating a higher tolerance of Gizda than Fermer.…”

Section: Discussionmentioning

confidence: 99%

Different Responses to Water Deficit of Two Common Winter Wheat Varieties: Physiological and Biochemical Characteristics

Popova

Mihailova

Geneva

et al. 2023

Since water scarcity is one of the main risks for the future of agriculture, studying the ability of different wheat genotypes to tolerate a water deficit is fundamental. This study examined the responses of two hybrid wheat varieties (Gizda and Fermer) with different drought resistance to moderate (3 days) and severe (7 days) drought stress, as well as their post-stress recovery to understand their underlying defense strategies and adaptive mechanisms in more detail. To this end, the dehydration-induced alterations in the electrolyte leakage, photosynthetic pigment content, membrane fluidity, energy interaction between pigment–protein complexes, primary photosynthetic reactions, photosynthetic and stress-induced proteins, and antioxidant responses were analyzed in order to unravel the different physiological and biochemical strategies of both wheat varieties. The results demonstrated that Gizda plants are more tolerant to severe dehydration compared to Fermer, as evidenced by the lower decrease in leaf water and pigment content, lower inhibition of photosystem II (PSII) photochemistry and dissipation of thermal energy, as well as lower dehydrins’ content. Some of defense mechanisms by which Gizda variety can tolerate drought stress involve the maintenance of decreased chlorophyll content in leaves, increased fluidity of the thylakoid membranes causing structural alterations in the photosynthetic apparatus, as well as dehydration-induced accumulation of early light-induced proteins (ELIPs), an increased capacity for PSI cyclic electron transport and enhanced antioxidant enzyme activity (SOD and APX), thus alleviating oxidative damage. Furthermore, the leaf content of total phenols, flavonoids, and lipid-soluble antioxidant metabolites was higher in Gizda than in Fermer.

“…Fresh leaves of WT, bhlh1, bhlh2, and bhlh1bhlh2 knockout lines at five weeks of age were stressed with withholding watering for 7 days for measurement of physiological parameters related to drought, including relative water content (RWC), MDA, and H 2 O 2 [50].…”

Section: Measurements Of Physiological Parametersmentioning

confidence: 99%

Co-Expression of JcNAC1- and JcZFP8-Improved Agronomic Traits of Tobacco and Enhanced Drought Resistance through NbbHLH1 and NbbHLH2

Niu,

Lai,

Wang

et al. 2023

Previous studies have identified numerous transcription factors involved in drought response, each of which play different roles in plants. The objective of the present study was to evaluate the effectiveness of two transcription factors on drought response in Jatropha curcas L., JcNAC1 and JcZFP8. The overexpression of these transcription factors in tobacco (Nicotiana benthamiana L.) improved drought resistance, but JcZFP8 delayed germination and JcNAC1 reduced biomass and yield. By constitutively co-expressing these two genes in tobacco, drought resistance was improved, and the negative effects of each of them were overcome. The transgenic plants with double-gene co-expression showed stronger drought tolerance with 1.76-fold greater accumulation of proline and lower H2O2 and malondialdehyde (MDA) content to 43 and 65% of wildtype (WT) levels, respectively. The expression levels of NbbHLH1 and NbbHLH2 genes upregulated linearly with the increased drought tolerance of double genes co-expression plants. In drought conditions, the leaf water contents of bhlh1, bhlh2, and bhlh1bhlh2 deletion mutants obtained by CRISPR-CAS9 knockout technique were maintained at 99%, 97%, and 97% of WT. The bhlh1bhlh2 was found with lower germination rate but with higher reactive oxygen levels (1.64-fold H2O2 and 1.41-fold MDA levels). Thus, the co-expression of two transcription factors with different functions overcame the adverse traits brought by a single gene and enhanced the shared drought-tolerant traits, which can provide guidance on theory and selection of gene combinations for the application of multi-gene co-expression in agriculture in the future.