Search

Extreme climatic conditions with extended drought periods and heatwaves are predicted to increase in frequency and severity in many regions of the world. Aside from this, other abiotic stress factors such as nutrient deficiency could pose a serious problem to plants when combined with other stressors resulting in more complex underpinning mechanisms. In the present study, we evaluated the response of Brassica napus to single and combined impacts of drought and heatwave (HW) under adequate or deprived (N-A and N-D) soil nutrient conditions. In addition, to get better insights in the plant response to combined stress, a post-stress period, pointing out a degree of the recovery after the cessation of stress, was also included. The results showed a different manner of single drought and heatwave action. The adverse effect of drought on leaf gas exchange was lagged on the growth and became more apparent only after recovery period with no obvious difference between different nutrient levels. Contrary, the growth response of nutrient-deprived plants to single HW was weak and in most cases, insignificant. Heatwave applied simultaneously with drought highly exacerbated the adverse effect of drought both under N-A and N-D conditions. Combined drought and heatwave stress resulted in the sharper decline of A sat and it was attributed to both stomatal and non-stomatal limitations. Interestingly, plants underwent combined drought and HW treatment under N-D conditions showed better aboveground growth recovery, compared to those grown under N-A conditions, while displayed far more diminished photochemistry of photosystem II and badly disturbed the C/N balance. This discrepancy came from the fact that soil nutrient deficiency, by itself, evoked strong stress under control climate conditions resulting in a dramatically slower aboveground growth of nutrient-deprived plant. In turn, although combined drought and HW stress had similar effect on the aboveground growth either under N-A or N-D conditions, the recovery of later one was better. These results highlight the necessity to look at plants' performance under unfavorable environmental conditions beyond the actual event, since it can be depended not only on the duration of exposure but also on the legacy effect after treatment., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Global climate change leads to increasing frequency of droughts, threatening the productivity and quality of forage plants. Therefore, this glasshouse experiment was conducted to investigate the effects of reoccurring droughts on productivity and nutritive value of alfalfa and hybrid fescue plants. Starting from 63 days after sowing, seedlings of plants were exposed to double drought‐recovery treatments, each separate period lasting for 1 week. At the end of each treatment, growth of above‐ and below‐ground dry weight, lipid peroxidation, total antioxidative capacity, content of polyphenols, soluble and insoluble carbohydrates and proteins, as well as elemental composition of shoots were investigated. The findings confirmed our hypothesis, as growth of both plant species were mostly insignificantly affected by subsequent drought events. Whereas effect on leave redox homeostasis and plant nutritive value was much stronger, highly depending on both plant species and the order of stress event. We found significant drought‐induced increase in the content of water‐soluble carbohydrates (WSCs), starch, soluble and insoluble proteins, and polyphenols. Water shortage tended to decrease and increase the content of most macro‐ and microelements in alfalfa and fescue, respectively. These effects were reversed by re‐watering with several exceptions, such as constant reduction of Ca content in alfalfa. To conclude, alfalfa was found to be more sensitive than fescue to the first drought, but able to recover after both stress events. The second drought‐initiated prolonged accumulation of WSC implies a shift in plants metabolism towards increased resistance and herewith nutritive value with respect to soluble sugars. [ABSTRACT FROM AUTHOR]

Intensity and frequency of heat waves (HW) accompanied by drought are increasing, however, still little is known about its effect on forage plants. A pot experiment was carried out in growth chambers in order to elucidate the multiple response of forage rape to combined HW and drought (HD) under current and elevated CO2 (HD + CO2). Forage rape was proved to be relatively HD‐resistant plant, with no significant and long‐term effects on shoot growth and photosynthetic performance, and effective stimulation of antioxidative system, especially in the case of HD + CO2 exposure. Activities of enzymes of ascorbate–glutathione cycle were further stimulated by elevated CO2 even after the termination of HD treatment. Nutritive value of forage rape was also positively affected, as was shown by elevated content of water‐soluble carbohydrates after exposure and starch after the period of recovery (up to 80% and 92%, respectively). Concentrations of most macro‐ and microelements were increased, and stabilized higher or equalized to control level after the period of recovery in a similar pattern for HD and HD + CO2 exposure. However, content of Ca was reduced and remained significantly lower (~20%). One of the most important negative and lagged HD effects was reduction of dry root biomass (~30%), most possibly induced by accumulation of non‐structural carbohydrates in shoot and was not mitigated by elevated CO2. To conclude, forage rape was proved to be a promising forage crop for the future climate with increased frequency of HWs; however, a special attention should be paid to the lagged effects, such as inhibition of root growth. [ABSTRACT FROM AUTHOR]

Intensity and frequency of heat waves (HW) accompanied by drought are increasing, however, still little is known about its effect on forage plants. A pot experiment was carried out in growth chambers in order to elucidate the multiple response of forage rape to combined HW and drought (HD) under current and elevated CO2 (HD + CO2). Forage rape was proved to be relatively HD‐resistant plant, with no significant and long‐term effects on shoot growth and photosynthetic performance, and effective stimulation of antioxidative system, especially in the case of HD + CO2 exposure. Activities of enzymes of ascorbate–glutathione cycle were further stimulated by elevated CO2 even after the termination of HD treatment. Nutritive value of forage rape was also positively affected, as was shown by elevated content of water‐soluble carbohydrates after exposure and starch after the period of recovery (up to 80% and 92%, respectively). Concentrations of most macro‐ and microelements were increased, and stabilized higher or equalized to control level after the period of recovery in a similar pattern for HD and HD + CO2 exposure. However, content of Ca was reduced and remained significantly lower (~20%). One of the most important negative and lagged HD effects was reduction of dry root biomass (~30%), most possibly induced by accumulation of non‐structural carbohydrates in shoot and was not mitigated by elevated CO2. To conclude, forage rape was proved to be a promising forage crop for the future climate with increased frequency of HWs; however, a special attention should be paid to the lagged effects, such as inhibition of root growth. [ABSTRACT FROM AUTHOR]