Responses and adaptation of xylem hydraulic conductivity to salt stress in Populus euphratica

doi:10.17521/cjpe.2015.0009

Abstract

Abstract: Aims

Soil salinity is a major limiting factor for plant establishment, development and productivity in arid environment. This study was conducted to determine the responses and adaptation of xylem hydraulic conductivity to salt stress in Populus euphratica in order to understand the mechanisms of stress resistance and restoration strategy of this species.

<i>Methods</i>

The responses and adaptation of hydraulic conductivity to different levels of salt stress (NaCl concentrations of 0, 0.05, 0.15 and 0.30 mol·L^-1) were investigated in P. euphratica seedlings. The testing plants were subjected to salt stresses for three months, and the stomatal conductance of leaves, hydraulic conductivity and vulnerability to cavitation of roots and stem xylem, anatomical structure of xylem vessels and root morphology and distribution were measured. The resulting data were analyzed to determine the relationships of salt stress with root uptake, hydraulic conductivity of xylem and foliar transpiration by using ANOVA, LSD and Pearson correlations.

<i>Important findings</i>

The roots of P. euphratica seedlings were more responsive to salt stress than stem and leaves. Root length and root tips were significantly inhibited by the salt stresses imposed. Under the salt stress, root hydraulic conductivity was significantly reduced and root xylem was more vulnerable to cavitation. The responses of stem xylem conductivity to salt stresses varied with the level of salt stress. Under a mild (0.05 mol·L^-1 NaCl) and moderate (0.15 mol·L^-1 NaCl) salt stress, Populus euphratica seedlings adjusted hydraulic conductivity in stem xylem by increasing the wall thickness of conduit and between conduits as well the wall mechanical strength to maintain norm growth. Under a severe salt stress (0.30 mol·L^-1 NaCl), hydraulic conductivity and safety and efficacy of water transportation of stem xylem in P. euphratica seedlings significantly decreased accompanied by reduced stomatal conductance of leaves, which eventually inhibited the plant growth.

Key words: xylem, hydraulic conductivity, vessel, root morphology, stomatal conductance

ZHOU Hong-Hua,LI Wei-Hong. Responses and adaptation of xylem hydraulic conductivity to salt stress in Populus euphratica[J]. Chin J Plan Ecolo, 2015, 39(1): 81-91.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2015.0009

https://www.plant-ecology.com/EN/Y2015/V39/I1/81

Figures/Tables 7

Fig. 1 Diurnal changes in stomatal conductance (Gs) of leaves in Populus euphratica seedlings under different concentration salt stresses (mean ± SE). Different letters indicate significant differences (p < 0.05, LSD). Control, 0 mol·L-1 NaCl; S1, 0.05 mol·L-1 NaCl; S2, 0.15 mol·L-1 NaCl; S3, 0.30 mol·L-1 NaCl.

Fig. 2 Hydraulic conductivity of roots and stems of Populus euphratica seedlings under different concentration salt stresses (mean ± SE). Ks0, initial hydraulic conductivity per unit volume. Ksmax, maximum hydraulic conductivity. Different letters indicate significant differences (p < 0.05, LSD). Control, 0 mol·L-1 NaCl; S1, 0.05 mol·L-1 NaCl; S2, 0.15 mol·L-1 NaCl; S3, 0.30 mol·L-1 NaCl.

Fig. 3 Curves of xylem vulnerability to cavitation in roots and stems of Populus euphratica seedlings under different concentration salt stresses (mean ± SE). PLC, percentage loss of hydraulic conductivity. Control, 0 mol·L-1 NaCl; S1, 0.05 mol·L-1 NaCl; S2, 0.15 mol·L-1 NaCl; S3, 0.30 mol·L-1 NaCl.

Fig. 4 Anatomical structure of stem xylem vessels in Populus euphratica seedlings under different concentration salt stresses (mean ± SE). Control, 0 mol·L-1 NaCl; S1, 0.05 mol·L-1 NaCl; S2, 0.15 mol·L-1 NaCl; S3, 0.30 mol·L-1 NaCl.

Fig. 5 Root morphology and distribution of Populus euphratica seedlings under different concentration salt stresses. A, control level (0 mol·L-1 NaCl solution); B, S1 level (0.05 mol·L-1 NaCl solution); C, S2 level (0.15 mol·L-1 NaCl solution); D, S3 level (0.30 mol·L-1 NaCl solution).

Fig. 6 Root characteristics of Populus euphratica seedlings under different concentration salt stresses (mean ± SE). Control, 0 mol·L-1 NaCl; S1, 0.05 mol·L-1 NaCl; S2, 0.15 mol·L-1 NaCl; S3, 0.30 mol·L-1 NaCl.

Table 1 Pearson correlation between root characteristics and hydraulic conductivity

	总根长 Total root length	总根尖数 No. of total root tips	0-5 mm根长 0-5 mm root length	0-5 mm根尖数 No. of 0-5 mm root tips	5-10 mm根长 5-10 mm root length	5-10 mm根尖数 No. of 5-10 mm root tips
最大比导率 k_smax	0.567^*	0.841^*	0.631^*	0.854^*	0.604^*	0.538^*
初始比导率 k_s0	0.494	0.800^*	0.565^*	0.815^*	0.538^*	0.460

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