High Temperature can Change Root System Architecture and Intensify Root Interactions of Plant Seedlings

Abstract

Climate change could alter plant aboveground and belowground resource allocation. Compared with shoots, we know much less about how roots, especially root system architecture (RSA) and their interactions, may respond to temperature changes. Such responses could have great influence on species'acquisition of resources and their competition with neighbors. We used a gel-based transparent growth system to in situ observe the responses of RSA and root interactions of three common subtropical plant species seedlings in Asia differing in growth forms (herb, shrub, and tree) under a wide growth temperature range of 18-34°C, including low and supra-optimal temperatures. Results showed that the RSA, especially root depth and root width, of the three species varied significantly in response to increased temperature although the response of their aboveground shoot traits was very similar. Increased temperature was also observed to have little impact on shoot/root resource allocation pattern. The variations in RSA responses among species could lead to both the intensity and direction change of root interactions. Under high temperature, negative root interactions could be intensified and species with larger root size and fast early root expansion had competitive advantages. In summary, our findings indicate that greater root resilience play a key role in plant adapting to high temperature. The varied intensity and direction of root interactions suggest changed temperatures could alter plant competition. Seedlings with larger root size and fast early root expansion may better adapt to warmer climates.

Keywords: root depth and width; root growth dynamics; root interaction; root system architecture; species competition; temperature change.

Figure 1

Root system architecture changes under different temperatures on the 84th day. (A) C. capsularis, (B) M. sepiaria, (C) O. glaberrima.

Figure 2

Temperature effects on seven root architecture traits and belowground biomass. TRL, total root length; RD, root depth; RW, root width; ARD, average root diameter; RBI, root branching intensity; RSF, root surface area; RV, root volume; BB, belowground biomass. (A–H) C. capsularis, (I–P) M. sepiaria, (Q–X) O. glaberrima. Error bars represent standard error (±SE). Different letters denote significant level at P < 0.05.

Figure 3

Temperature effects on the dynamics of two root size-related metrics and their absolute expansion rate (AER) of two species under different temperature treatments. Graphs show predicted values with 95% confidence intervals (gray curves) for (A–D) C. capsularis, (E–H) M. sepiaria.

Figure 4

Temperature effects on shoot traits and the ratio of shoot biomass to root biomass. (A–E) C. capsularis, (F–J) M. sepiaria, (K–O) O. glaberrima. Error bars represent standard error (±SE). Different bar annotations denote significant differences (P < 0.05).

Figure 5

Temperature effects on root relative interaction intensity (RII) with focal species C. capsularis. Graphs show RII measured by (A) Total biomass, (B) BB, belowground biomass, (C) TRL, total root length, (D) RSF, root surface area, (E) RV, root volume, (F) RD, root depth, (G) RW, root width, (H) ARD, average root diameter and (I) RBI, root branching intensity. The bars are grouped by species-pair combination treatments and different bars represent different temperature treatments. Asterisks indicate one-sample t-tests for the difference from zero. *, P < 0.05; **, P < 0.01; ***, P < 0.001.

Figure 6

Temperature effects on root relative interaction intensity (RII) with focal species M. sepiaria. Graphs show RII measured by (A) Total biomass, (B) BB, belowground biomass, (C) TRL, total root length, (D) RSF, root surface area, (E) RV, root volume, (F) RD, root depth, (G) RW, root width, (H) ARD, average root diameter and (I) RBI, root branching intensity. The bars are grouped by species-pair combination treatments and different bars represent different temperature treatments. Asterisks indicate one-sample t-tests for the difference from zero. *, P < 0.05; **, P < 0.01; ***, P < 0.001..