Interspecific Differences in Physiological and Biochemical Traits Drive the Water Stress Tolerance in Young Morus alba L. and Conocarpus erectus L. Saplings

Abstract

Mitigating climate change requires the identification of tree species that can tolerate water stress with fewer negative impacts on plant productivity. Therefore, the study aimed to evaluate the water stress tolerance of young saplings of C. erectus and M. alba under three soil water deficit treatments (control, CK, 90% field capacity, FC, medium stress MS, 60% FC and high stress, HS, 30% FC) under controlled conditions. Results showed that leaf and stem dry weight decreased significantly in both species under MS and HS. However, root dry weight and root/shoot ratio increased, and total dry weight remained similar to CK under MS in C. erectus saplings. Stomatal conductance, CO₂ assimilation rate decreased, and intrinsic water use efficiency increased significantly in both species under MS and HS treatments. The concentration of hydrogen peroxide, superoxide radical, malondialdehyde and electrolyte leakage increased in both the species under soil water deficit but was highest in M. alba. The concentration of antioxidative enzymes like superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase also increased in both species under MS and HS but was highest in C. erectus. Therefore, results suggest that C. erectus saplings depicted a better tolerance to MS due to an effective antioxidative enzyme system.

Keywords: drought stress; leaf gas exchange; mulberry; osmolytes accumulation; water use efficiency.

Figure 1

Mean dry weight production in leaves dry weight (A), stem dry weight (B), root dry weight (C) and total dry weight (D) under control (CK), Medium (MS) and high (HS) water deficit treatments in C. erectus and M. alba. All the attributes were tested using a two-way ANOVA for species effect (S-effect), treatment (T-effect) and interaction (S × T) effects. All values represent the means (±SE) of species in various combinations. Small letters set in bold represent significant difference within each species tested using Dunnett’s test. All the tests were taken significant at p < 0.005.

Figure 2

Means values of various gas exchange parameters such as CO₂ assimilation rate (A), stomatal conductance (B), intrinsic water use efficiency (C) under control (CK), Medium (MS) and high (HS) water deficit treatments in C. erectus and M. alba. All the attributes were tested using a two-way ANOVA for species effect (S-effect), treatment (T-effect) and interaction (S × T) effects. All values represent the means (±SE) of species in various combinations. Small letters set in bold represent significant difference within each species tested using Dunnett’s test. All the tests were taken to be significant at p < 0.005.

Figure 3

Production of various oxidants, such as hydrogen peroxide, H₂O₂ (A) and superoxide radical, O₂⁻ (B), along with malondialdehyde contents, MDA(C) and electrolyte leakage, EL% (D) under control (CK), Medium (MS) and high (HS) water deficit treatments in C. erectus and M. alba. All the attributes were tested using a two-way ANOVA for species effect (S-effect), treatment (T-effect) and interaction (S × T) effects. All values represent the means (±SE) of species in various combinations. Small letters set in bold represent significant difference within each species tested using Dunnett’s test. All the tests were taken to be significant at p < 0.005.

Figure 4

Mean activity various antioxidants enzyme concentration (A) superoxide dismutase, SOD, (B) peroxidase, POD, (C) catalase, CAT and (D) ascorbate peroxidase, APX under control (CK), Medium (MS) and high (HS) water deficit treatments in C. erectus and M. alba. All the attributes were tested using a two-way ANOVA for species effect (S-effect), treatment (T-effect) and interaction (S × T) effects. All values represent the means (±SE) of species in various combinations. Small letters set in bold represent a significant difference within each species tested using Dunnett’s test. All the tests were taken significant at p < 0.005.