Phenotypic Plasticity Strategy of Aeluropus lagopoides Grass in Response to Heterogenous Saline Habitats

Abstract

Understanding the response variation of morphological parameters and biomass allocation of plants in heterogeneous saline environments is helpful in evaluating the internal correlation between plant phenotypic plasticity mechanism and biomass allocation. The plasticity of plants alters the interaction among individuals and their environment and consequently affects the population dynamics and aspects of community and ecosystem functioning. The current study aimed to assess the plasticity of Aeluropus lagopoides traits with variation in saline habitats. Understanding the habitat stress tolerance strategy of A. lagopoides is of great significance since it is one of the highly palatable forage grass in the summer period. Five different saline flat regions (coastal and inland) within Saudi Arabia were targeted, and the soil, as well as the morphological and physiological traits of A. lagopoides, were assessed. Comprehensive correlation analyses were performed to correlate the traits with soil, region, or among each other. The soil analysis revealed significant variation among the five studied regions for all measured parameters, as well as among the soil layers showing the highest values in the upper layer and decreased with the depth. Significant differences were determined for all tested parameters of the morphological and reproductive traits as well as for the biomass allocation of A. lagopoides, except for the leaf thickness. In the highly saline region, Qaseem, A. lagopoides showed stunted aerial growth, high root/shoot ratio, improved root development, and high biomass allocation. In contrast, the populations growing in the low saline region (Jizan) showed the opposite trend. Under the more stressful condition, like in Qaseem and Salwa, A. lagopoides produce low spikes in biomass and seeds per plant, compared to the lowest saline habitats, such as Jouf. There was no significant difference in physiological parameters except stomatal conductance (g_s), which is highest in the Jizan region. In conclusion, the population of A. lagopoides is tolerant of harsh environments through phenotypic plasticity. This could be a candidate species to rehabilitate the saline habitats, considering saline agriculture and saline soil remediation.

Keywords: biomass allocation; desalination; functional traits; halophytes; saline flat regions.

Figure 1

Different studied flat saline regions, (A) Qareenah, (B) Qaseem, (C) Salwa, (D) Jouf, and (E) Jizan. The left is an overview, and the right is a close view of A. lagopoides.

Figure 2

Comparison of shoot traits of Aeluropus lagopoides growing in different saline flat regions of Saudi Arabia. Values are average (n = 75), and the bar represents the standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. ** p < 0.01*** p < 0.001.

Figure 3

Measured root traits for Aeluropus lagopoides growing in different saline flat regions of Saudi Arabia. Values are average (n = 75), and the bar represents the standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. *** p < 0.001. FW: fresh weight, DW: dry weight.

Figure 4

Comparison of leaf traits for Aeluropus lagopoides growing in different saline flat regions of Saudi Arabia. Values are average (n = 10), and the bar represents standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. SLA: specific leaf area, LDMC: leaf dry matter content. FW: fresh weight, DW: dry weight. *** p < 0.001, and “ns” for p > 0.05.

Figure 5

Reproductive traits for Aeluropus lagopoides growing in different saline flat regions of Saudi Arabia. Values are average (n = 75), and the bar represents the standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. * p < 0.05, ** p < 0.01, *** p < 0.001. FW: fresh weight, DW: dry weight.

Figure 6

Ecophysiological parameters of Aeluropus lagopoides growing in different saline flat regions of Saudi Arabia. Values are average (n = 75), and the bar represents the standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. *** p < 0.001, and “ns” for p > 0.05. FW: fresh weight.

Figure 7

Biomass allocation among Aeluropus lagopoides collected from different saline flat regions of Saudi Arabia, based on dry matter. Values are average (n = 75), and the bar represents the standard error. Different letters among regions showed significant differences at p < 0.05 after Duncan’s test. *** p < 0.05.

Figure 8

Principal component analysis (PCA) of the measured traits (shoot, represented with red arrows, root represented with brown arrows, reproductive traits represented with blue arrows of Aeluropus lagopoides within different saline flat regions (represented with yellow circle) of Saudi Arabia.

Figure 9

Canonical correspondence analysis (CCA) showing the correlations among the soil variables of different layers separately ((a): 0–15 cm, (b): 15–30 cm, and (c): 30–45 cm layers), regions, and morphological traits of A. lagopoides. SFW: shoot fresh weight, SDW: shoot dry weight, RFW: root fresh weight, RDW: root dry weight, lvs/p; number of leaves per plant, SLA: specific leaf area, Spk/p: number of spikes per plant, AvgSpkL: average spike length, RA: root area, LT: leaf thickness, SL: shoot length, RL: root length, Stl/p: number of stolon per plant, LDMC: leaf dry matter content, LFW: leaf fresh weight, LFW: leaf fresh weight, LDW: leaf dry weight, SpkFW: spike fresh weight, SpkDW: spike dry weight, ASL: average stolon length.

Figure 10

Agglomerative hierarchical clustering (AHC) and heatmaps of the studied parameters within different saline flat regions of Aeluropus lagopoides. (A) AHC and (B) heatmap based on the soil variables, (C) AHC and (D) heatmap based on the morphological and reproductive traits. EC: electrical conductivity, OM: organic matter, SLA: specific leaf area, LDMC: leaf dry matter content.