Evaluation of the physiological and biochemical response of cultivars Lens culinaris to drought stress and re-irrigation

IntroductionDrought stress is one of the most important abiotic factors that can limit plant growth and yield. The response of plants to water limitation has been evaluated based on genetic, biochemical, and morpho-physiological traits. Plants are constantly affected by drought stress and re-irrigation. Therefore, rapid and efficient recovery from water deficit stress may be one of the key determinants of drought adaptation in plants. The aim of this research was the evaluation of drought stress tolerance and recovery in lentil cultivars after stress conditions.Materials and methodsIn order to evaluate the response of lentil cultivars to drought stress and re-irrigation, a factorial split-plot experiment based on a randomized complete block design with three replications was conducted in the greenhouse. Drought stress was applied at the flowering stage. The factors include 4 lentil cultivars (Namin landrace and Sepehr, Gachsaran, and Kimiya cultivars), drought stress (control (irrigation at 80% FC), medium stress (irrigation at 55% FC) and severe stress (irrigation at 30% FC)) and 3 sampling times (three and six days after drought and recovery (two days after re-irrigation)). All the plants were allowed to grow until the flowering stage (50 days after sowing) under well-watered conditions (80% FC (field capacity) of soil). Afterward, the plants were randomly assigned to three different groups and were exposed to different irrigation regimes including the control (well-watered and maintained at 80% FC), medium stress (watered and maintained at 55% FC), and severe drought stress (watered and maintained at 30% FC). The moisture content of the soil was controlled and maintained within a defined range using the weight method. Stress conditions were kept until the crop maturity and harvesting stage. The leaf samples from 5 seedlings of each pod were collected at 3 and 6 days after drought stress exposure, and two days after re-irrigation and used for physiological and biochemical analysis. The samples immediately were frozen in liquid nitrogen and stored at −80°C until analysis.Results and discussionThe results showed that adaptation to drought stress was closely related to the recovery ability of plants. Drought stress caused a decrease in chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein and proline, yield, and yield components. The reduction of these traits was more remarkable at six days after stress. However, during the recovery time remarkable increase was observed in these traits. The results showed that the correlation between H2O2 and MDA was significant and positive. Furthermore, drought stress increased the amount of H2O2 and MDA, which increased the activity of antioxidant enzymes (catalase, polyphenol oxidase, and peroxidase). An increase in the intensity and duration of the drought stress also caused an increase in proline (63%), H2O2, (19%), and MDA (110%) content, and the activity of CAT (33%), PP0 (56%), and POX (24%) compared to the control treatment. An increase in the intensity and duration of the drought stress also caused an increase in H2O2 and MDA content and the activity of antioxidant enzymes. In addition, in the recovery conditions, a significant reduction in the destructive effects of stress (H2O2, MDA content) and the activity of antioxidant enzymes was visible. The results of the present study indicated that the effects of drought stress on lentil cultivars' yield and yield components (seed numbers, number of pods, 100-seed weight, and seed yield) were varied. Drought stress at the flowering stage decreased the number of seeds (20%) and pods per plant (37%), and 100-seed weight (16%), which led to 29% yield losses. Although the Gachsaran cultivar had the highest yield under normal conditions. However, under drought stress conditions Gachsaran and Sepehr cultivars showed the highest plant yield. On the other hand, the Namin landrace exhibited the lowest yield (40%) under stress conditions.ConclusionThe water stresses markedly increased the reactive oxygen species (ROS) level and impaired the biosynthesis of the photosynthetic pigment, resulting in the reduction of plant growth and yield with fewer seeds and pods number per plant. However, re-irrigation (recovery) remarkably improved plant growth and reduced the negative effects of drought stress, such as reducing the amount of MDA and H2O2 and improving the activity of antioxidant enzymes and proline content. In conclusion, based on physiological traits Gachsaran, and Sepehr cultivars seem to be suitable cultivars for culture in the regions challenged with water deficit stress.