Five cultivars ABA content remained unaffected at mild stress level in both the plant species but showed significantly higher content in roots and leaves of maize than wheat at moderate and high stress levels. Berseem clover (Trifolium alexandrinum L.) is an important crop in semi-arid regions; its herbage and seed yields are often reduced by water stress. At the time of planting, three drought treatments were applied to the mesocosms by trimming the plastic pot to three different heights: (i) 222 mm (no trimming—control); (ii) 105 mm (moderate drought); or (iii) 55 mm (severe drought). The combined impacts from drought and herbivory on various plant traits were synergist, additive or antagonistic (greater than, equal to or less than expected effects, respectively, based on single stressor effect sizes). Breeding strategies should therefore be undertaken to increase the GSH content of rice plants as a means to increase drought tolerance. Within each group of three bars, different lower case letters indicate significant differences between herbivory treatments, and within each year different capitalized letters indicate significant differences between drought treatments. For the first growing season, we used seedlings from all the measured blocks, and for the second season we based our calculation on the seedlings with sustained drought. Our direct comparison of these two stressors revealed that each stressor targeted a suite of plant traits related to plant C balance, albeit the magnitude of impact from drought was generally greater. Drought and herbivory are two common environmental stressors that impact seedling growth and morphology. Consequently, these two synergistic effects appeared to help the establishing seedlings cope with the impacts from multiple stressors. Looks like you’ve clipped this slide to already. However, the surface soil after scarification retains less water than undisturbed soils (Nilsson and Örlander 1995), which can impose water stress on seedlings, and may increase their susceptibility to attack by any remaining herbivores (Mattson and Haack 1987, Selander and Immonen 1992, Dobbertin et al. This review also briefly discusses the importance of the use of specific stress inducible Forests typically experience a mix of anthropogenic, natural and climate-induced stressors of different intensities, creating a mosaic of stressor combinations across the landscape. For gas exchange parameters during the first year (Figure 2, left subpanels), photosynthesis was negatively affected by herbivory (P < 0.01), conductance was negatively affected by both drought (P = 0.05) and herbivory (P < 0.01) and WUE was affected by drought (P < 0.001), herbivory (P = 0.05) and their interaction (P = 0.04). The interactive effect of drought and herbivory on WUE appeared due to the positive effect of herbivory on WUE only for seedlings given the moderate drought treatment (Figure 2c, left subpanel). The mesocosms were monitored regularly (see Methods 1 available as Supplementary Data at Tree Physiology Online) until harvest, 19 months after initiation. 2002, Gaylord et al. Traits (means ± 1 SE) include whole-plant mass (a), shoot mass (b), root mass (c), stem diameter (d), height (e) and root-to-shoot ratio (f). This has been observed under field conditions as well, in which unusually dry conditions during the previous year made pine weevil damage to establishing seedlings nearly negligible (Nilsson and Örlander 1995). The scarring was done twice on seedlings: at the time of planting (June) and then again at the end of the first growing season (September). An increase in evaporative surface area is a common occurrence under field conditions following typical mounding site preparation (Sutton 1993). Learn more. The biology and ecology of the large pine weevil. 2008). All plant material was then dried at 60 °C for at least 48 h and weighed (±0.1 mg). More rain, sleet, hail, and snow can occur where there are moist, low-pressure air systems. Drought and herbivory are two stressors that commonly co-occur in forested ecosystems, and have the potential to ‘overlap’ in their impacts on various plant traits and processes. For example, low-level water stress may induce short-term stomatal closure (Chaves et al. Stress from drought and herbivory have the potential to cause serious disruptions to many physiological processes of establishing seedlings (Desprez-Loustau et al. We applied three levels of each stressor (control, moderate and severe) to all seedlings during their first growing season. In contrast, wheat possessed more activity of catalase in its roots as well as leaves in comparison to maize. When drought stress was relieved during the second year, these severely droughted plants had a relatively high supply of water relative to their needs (i.e., a self-correcting mechanism; Kozlowski and Pallardy 2002), thus making the magnitude of recovery greater and more evident. 2004). Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Second, differences in recovery could be explained by greater carbohydrate accumulation in the severely (compared with moderately) droughted plants because growth is more sensitive than photosynthetic C assimilation to drought (Sala et al. All pairwise comparisons were made on untransformed data. 2006). This was most evident for total, shoot and root biomass, as well as for gas exchange rates, in which the expected reductions in performance from two stressors were not as severe as expected. Similarly, bark-feeding insects have the potential to impede tree seedling C balance and growth, although the mechanisms may differ from drought (i.e., consumption of C assimilates during phloem transport). It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. Disturbances from herbivorous insects are among the most common natural stressors in boreal forests (Schowalter et al. 2006, Valois et al. The berseem cultivars examined showed differences in plant to drought includes both phenotypic and genotypic changes. Many traits conferring dehydration avoidance and dehydration tolerance are available, but integrated traits, expressing at a high level of organization are suggested to be more useful in crop improvement programs. to cope with negative changes in environment, including increased water deficit. Stem diameters at the base of the stem, shoot lengths and needle lengths were measured on each seedling at outplanting, and at the end of the first and second growing season. The main genetic difference was recorded for turgor maintenance capacity. We measured light-saturated instantaneous net photosynthesis (A, μmol CO2 m−2 s−1), stomatal conductance to water vapor (gs, mol H2O m−2 s−1) and water-use efficiency (WUE; A gs−1) using a portable photosynthesis instrument equipped with a CO2 controller and an attached light source (LI-6400, Li-Cor Biosciences, Inc., Lincoln, NE, USA). promoters and the future prospects of transgenic plants with improved agronomic traits. When the means (and their 95% confidence limits) were greater than or less than the zero line they were considered synergistic or antagonistic, respectively.