Salinity reduces plant biomass and may lead to death when severe. To cope with the negative effects of this stress, plant species present specific physiological or biochemical responses. In this work, we hypothesized that spraying salt-stressed thyme leaves with K+ and Ca2+ could mitigate the negative effects of salinity on plant growth and metabolism. To test this hypothesis, we grew thyme plants under salinity stress for two and four weeks before applying foliar sprays. Also, to test the effect of stress relief, treated plants were allowed two weeks of recovery after four weeks of salt stress. In general, after two and four weeks of salinity stress, the leaf fresh weight of thyme plants was reduced by 31 and 43%, respectively. Salinity also decreased the relative water content, water, and osmotic potentials and led to ion imbalances and nutrient deficiencies. Salinity altered concentration of some essential oils, but leaf antioxidant contents remained fairly stable, except for a significant increase for plants under NaCl?+?KCl two weeks after treatment. Our results indicated that stressed plants accumulated significantly more soluble sugars and amino acids in comparison with the control. Foliar sprays with KCl and CaCl2 reversed the negative effects of salinity on plant biomass and induced the accumulations of compatible solutes. Moreover, concentrations of some essential oils and gallic acid increased in sprayed plants, but these effects were dependent on the type and duration of the treatment. Overall, spraying leaves with K+ and Ca2+ was able to mitigate salinity stress in Thymus vulgaris even during the recovery period. 相似文献
Quinoa (ChenopodiumquinoaWilld.) is a highly nutritious Andean seed crop which shows great potential to grow under a range of hostile environments. The objective of this study was to investigate the differences of drought tolerance of a Bolivian (Achachino) and a Danish (Titicaca) variety, and especially drought‐related adaption strategies. Soil water status was expressed as the fraction of transpirable soil water (FTSW). Relative stomatal conductance (RSC), relative transpiration (RT) and relative leaf water potential (RLW) were calculated by determining stomatal conductance, transpiration rate and leaf water potential of the drought‐treated plants relative to those of fully irrigated plants. The responses of RSC, RT and RLW to decreasing FTSW were described by a linear‐plateau model. The critical value of FTSW was the threshold of FTSW where the parameters studied decreased. The thresholds increased CS for stomatal conductance, CT for transpiration and CLfor leaf water potential. Achachino showed significantly lower CT and CL when compared with Titicaca, implying that transpiration and leaf water potential were less affected under mild drought conditions in the Bolivian variety. CS in Achachino was significantly higher than CL and CT, which indicated that stomatal conductance declined before transpiration and leaf water potential were reduced. Such difference was found in Titicaca where reduction of leaf area had more effect on transpiration than stomatal closure. Slower growth rate and smaller leaf area in combination with a lower stomatal conductance was found to contribute to drought resistance in Achachino. ABA concentration in the xylem sap tended to increase in both varieties after 2 days onset of drought, prior to decline in leaf water potential. Titicaca showed significantly (P < 0.05) higher ABA concentration when compared with Achachino under both fully irrigated and drought conditions. Titicaca had higher xylem nutrient concentration in comparison with Achachino in both fully‐watered and drought plants at day 2 after onset of soil drying. It was concluded that Titicaca was more sensitive to progressive drought than Achachino which avoided water loss by means of lower growth rate and smaller leaf area. 相似文献
Five-month-old Pinus halepensis Mill. seedlings were subjected to 4 irrigation treatments for 8 weeks. After the treatments, morphological and physiologicalattributes assessed included height, diameter, dry weight, water relations parameters, and determination of N, P, K, soluble carbohydrates, and starch concentrations. The remaining seedlings were field planted. Survival and height growth were recorded forfour growing seasons after planting. The mostsignificant effect of irrigation was onmorphology. Increased irrigation lead toseedlings with significantly higher height,root collar diameter and shoot and rootbiomass. Starch and soluble carbohydrateconcentrations were also affected byirrigation. However, parameters derived frompressure-volume curves were not significantlydifferent among treatments, nor were N, P, andK concentrations. There were no differencesamong treatments for survival in the field,which was highly related to summer rainfall. Incomparison, absolute and relative heightgrowth showed some significant but minordifferences among treatments. 相似文献
The combined effect of drought and light on different physiological and biochemical traits was assessed in cork oak (Quercus suber L.) seedlings grown under two levels of light availability and submitted to a long-standing drought. Watering was withdrawn after germination and seedlings were allowed to dry to a water content of ca. 50% of field capacity. At this point, water-stressed seedlings were grown under moderate drought and two light regimes: high light (HL—50%) and low light (LL—2%). Soil water in control plants was kept close to field capacity (90–100%) for both light environments. Water-relations parameters derived from P–V curves, gas exchange and water status at predawn (Ψpd) were evaluated at twice during the experiment. Nitrogen and chlorophyll contents were determined in the same leaves used for the gas exchange measurements. In addition, maximum rate of carboxylation (Vcmax) and electronic transport (Jmax) were derived from A–Ci curves in well-watered seedlings.
The variation on moisture availability during the experiment was the same under both light environments. In control plants, Ψpd was over −0.3 MPa at the two harvests, while stressed seedlings decreased to −0.9 MPa, with no differences between light treatments. Water stress decreased osmotic potentials at full (Ψπ100) and zero turgor (Ψπ0). The regressions between both potentials and Ψpd showed a higher intercept in shade grown seedlings. This fact will point out the higher osmoregulation capacity in sun seedlings whatever water availability.
Nitrogen investment on a per leaf mass (Nmass), chlorophyll content (Chlmass) and SLA tended to show a typical pattern of sun-shade acclimation. Thus, the three parameters increased with shade. Only for Nmass there was a significant effect of watering, since water stress increased Nmass.
LL plants showed a lower photosynthetic capacity in terms of maximum net photosynthesis at saturating light (Amax), which was related to a decrease in Vcmax and Jmax. Both parameters varied with specific leaf area (SLA) in a similar way. The low-light environment brought about a higher nitrogen investment in chlorophyll, while under high-light environment the investment was higher in carboxylation (Vcmax) and electronic transport (Fmax).
Stomatal conductance to water vapour (gwv) and Amax were lower in low-light seedlings independently of watering. In addition, there was a trend to keep higher intrinsic water use efficiency (IWUE) under high light environment. The increase of IWUE under water stress was higher in HL seedlings. This was as consequence of the steeper decline in gwv as Ψpd decreased. The decrease of Amax with Ψpd occurred in a similar way in LL and HL seedlings. Thus, the HL seedlings tended to sustain a higher ability to increase IWUE than LL seedlings when they were submitted to the same water stress. 相似文献