A Preliminary Study on the Whole-Plant Regulations of the Shrub Campylotropis polyantha in Response to Hostile Dryland Conditions

Abstract

Drylands cover more than 40% of global land surface and will continue to expand by 10% at the end of this century. Understanding the resistance mechanisms of native species is of particular importance for vegetation restoration and management in drylands. In the present study, metabolome of a dominant shrub Campylotropis polyantha in a dry-hot valley were investigated. Compared to plants grown at the wetter site, C. polyantha tended to slow down carbon (C) assimilation to prevent water loss concurrent with low foliar reactive oxygen species and sugar concentrations at the drier and hotter site. Nitrogen (N) assimilation and turn over were stimulated under stressful conditions and higher leaf N content was kept at the expense of root N pools. At the drier site, roots contained more water but less N compounds derived from the citric acid cycle. The site had little effect on metabolites partitioning between leaves and roots. Generally, roots contained more C but less N. Aromatic compounds were differently impacted by site conditions. The present study, for the first time, uncovers the apparent metabolic adaptations of C. polyantha to hostile dryland conditions. However, due to the limited number of samples, we are cautious about drawing general conclusions regarding the resistance mechanisms. Further studies with a broader spatial range and larger time scale are therefore recommended to provide more robust information for vegetation restoration and management in dryland areas under a changing climate.

Keywords: carbohydrates; climate change; drought; drylands; metabolome; nitrogen; partitioning; roots.

Figure 1

Contents of water (a) and hydrogen peroxide (b) in leaf (green bars) and root (yellow bar) of Campylotropis polyantha at site with optimal conditions (OPT, without hatching) and site with arid conditions (AR, hatched bars). Asterisks indicate significant differences between the two sites within the same tissue (*, p < 0.05; **, p < 0.01). Data are presented as means ± SE (n = 6) on a dry weight basis.

Figure 2

Total carbon (a), nitrogen (b) contents and their ratios (c), soluble protein (d), total amino acid (e), soluble sugar (f), δ¹³C (g) and δ¹⁵N (h) in leaf (green bars) and root (yellow bar) of Campylotropis polyantha at site with optimal conditions (OPT, without hatching) and site with arid conditions (AR, hatched bars). Asterisks indicate significant differences between the two sites within the same tissue (*, p < 0.05; **, p < 0.01). Data are presented means ± SE (n = 6) on a dry weight basis.

Figure 3

Venn diagram showing metabolites abundant in leaves and roots of Campylotropis polyantha at site with optimal conditions (OPT) and site with arid conditions (AR). The numbers indicate the number of shared compound(s) of the groups.

Figure 4

Fold change (log₂) of metabolites in leaves (left panels) and roots (right panels) of Campylotropis polyantha between the arid site (AR) and the optimal site (OPT), respectively. Asterisks indicate significant differences between sites within the same tissue, and between tissues within the same site (*, p < 0.05; **, p < 0.01; ***, p < 0.001; na, the metabolite was not detectable). Data are presented means ± SE (n = 6) on a dry weight basis.

Figure 5

Clustering of all physiological and metabolic parameters in leaves (L, circle) and roots (R, triangle) of Campylotropis polyantha in the optimal site (OPT) and the arid site (AR). Semi-transparent shadings indicate 95% confidence regions.