Effects of clonal integration on growth of stoloniferous herb Centella asiaticasuffering from heterogeneous heavy metal Cd<sup>2+</sup>stress

doi:10.3724/SP.J.1258.2011.00864

Abstract

Abstract:

Aims A pot experiment to examine the effects of clonal integration on growth of the stoloniferous herb Centella asiaticasuffering from heterogeneous heavy metal Cd²⁺stress was conducted to address two questions: (1) does clonal integration alleviate the negative effects on growth of clonal plants suffering from heterogeneous heavy metal stress; and (2) do the ramets growing in unfavorable microhabitats incur increased photosynthetic efficiency in the connected ramets?

Methods Relatively young, distal ramets of C. asiatica were assigned to normal or Cd²⁺ stressed soil, and the stolon connections between the relatively old proximal ramets and the young distal ramets were either severed or left intact. The net photosynthetic rate (P_n), chlorophyll fluorescence (maximum quantum yield of PSII, F_v/F_m) and chlorophyll contents of distal ramets and P_n of proximal ramets were measured. The growth performance of distal and proximal ramets was investigated at the end of the experiment.

Important findings Cd²⁺stress treatment significantly decreased the P_n, F_v/F_m, chlorophyll contents and growth of distal ramets. Clonal integration significantly alleviated the negative effect of Cd²⁺stress to distal ramets in terms of P_n, F_v/F_m, chlorophyll contents and biomass of distal ramets. There was no significant cost to the connected proximal ramets, and clonal integration did not incur increased photosynthetic efficiency in the proximal ramets. In addition, clonal integration significantly decreased root to shoot ratio of distal ramets suffering from Cd²⁺stress, and reduced the uptake of the heavy metal. Petiole length of proximal and distal ramets was not significantly affected by stolon severing and Cd²⁺stress. It is suggested that clonal integration may enhance growth of clonal plants suffering from heterogeneous heavy metal stress.

Key words: adaptation strategy, Cd²⁺ stress, clonal integration, photosynthetic efficiency, stolon severing

LIU Fu-Jun, LI Yun-Xiang, LIAO Yong-Mei, CHEN Jin-Song, QUAN Qiu-Mei, GONG Xin-Yue. Effects of clonal integration on growth of stoloniferous herb Centella asiaticasuffering from heterogeneous heavy metal Cd<sup>2+</sup>stress[J]. Chin J Plant Ecol, 2011, 35(8): 864-871.

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URL: https://www.plant-ecology.com/EN/10.3724/SP.J.1258.2011.00864

https://www.plant-ecology.com/EN/Y2011/V35/I8/864

Figures/Tables 7

Fig. 1 Schematic representation of the experimental design. NS-CS, stolon connections left intact and distal ramets are assigned to Cd2+ stressed soil; NS||CS, stolon connections are severed and distal ramets are assigned to Cd2+ stressed soil; NS-NS, stolon connections are left intact and distal ramets are assigned to normal soil; NS||NS, stolon connections are severed and distal ramets are assigned to normal soil.

Table 1 Results of two-way analysis of variance on the effects of stolen severing (S), Cd2+ stress (C) and their interaction (S × C) on petiole length, leaf area, number of ramets, biomass and root to shoot ratio of the proximal, distal ramets and/or the whole clonal fragments of Centella asiatica

	叶柄长 Petiole length	叶面积 Leaf area	分株数 Number of ramets	生物量 Biomass	根冠比 Root to shoot ratio
近端分株 Proximal ramets, df(1,12)
S	0.14^ns	0.01^ns	25.00^**	0.56^ns	1.50^ns
C	0.01^ns	0.02^ns	1.00^ns	0.16^ns	2.27^ns
S × C	0.04^ns	0.08^ns	1.00^ns	1.55^ns	2.39^ns
远端分株 Distal ramets, df(1,12)
S	0.40^ns	1.84^ns	6.25^*	0.96^ns	1.83^ns
C	3.46^ns	11.01^**	20.25^**	39.38^**	9.08^*
S × C	0.08^ns	1.45^ns	2.25^ns	5.25^*	3.44^ns
克隆片段 Whole clonal fragments, df(1,16)
S	-	1.58^ns	0.00^ns	1.74^ns	-
C	-	21.66^**	10.67^*	34.70^**	-
S × C	-	3.20^ns	0.67^ns	4.95^*	-

Fig. 2 Leaf area (A), number of ramets (B) and biomass (C) of the proximal, distal ramets and the whole clonal fragments (mean ± SE). For the proximal and distal ramets, the same lowercase letters are not significantly different at p = 0.05, for the whole clonal fragments, the same Greek letters are not significantly different at p = 0.05. NS-CS, stolon connections left intact and distal ramets are assigned to Cd 2+ stressed soil; NS||CS, stolon connections are severed and distal ramets are assigned to Cd2+ stressed soil; NS-NS, stolon connections are left intact and distal ramets are assigned to normal soil; NS||NS, stolon connections are severed and distal ramets are assigned to normal soil.

Fig. 3 Petiole length (A) and root to shoot ratio (B) of the proximal and distal ramets (mean ± SE). The bars with the same lowercase letters are not significantly different at p = 0.05. NS-CS, stolon connections left intact and distal ramets are assigned to Cd 2+ stressed soil; NS||CS, stolon connections are severed and distal ramets are assigned to Cd2+ stressed soil; NS-NS, stolon connections are left intact and distal ramets are assigned to normal soil; NS||NS, stolon connections are severed and distal ramets are assigned to normal soil.

Table 2 Results of Two-way repeated-measure analysis of variance, with stolen severing (S) and Cd2+ stress (C) as between-subject effects, for differences in net photosynthesis rate (Pn), chlorophyll fluorescence (maximum quantum yield of photosystem II, Fv/Fm) and chlorophyll contents (SPAD values) between distal ramets and Pn between proximal ramets of Centella asiatica

	近端分株 Proximal ramets		远端分株 Distal ramets
	P_n		P_n		F_v/F_m		SPAD
	df	F	df	F	df	F	df	F
组间效应 Between-subject effects
S	1	0.03^ns	1	6.49*	1	5.71*	1	5.18*
C	1	0.54^ns	1	66.00**	1	5.89*	1	35.29**
S × C	1	0.39^ns	1	10.96 *	1	2.38^ns	1	1.80^ns
误差 Error	8		8		8		12
组内效应 Within-subject effects
次数 Time	3	0.41^ns	3	0.24^ns	2	0.84^ns	3	5.58*
切断×次数 S × time	3	0.17^ns	3	0.17^ns	2	2.20^ns	3	0.48 ^ns
镉胁迫×次数 C × time	3	0.14^ns	3	2.75^ns	2	5.17^ns	3	5.66*
切断×镉胁迫×次数 S × C × time	3	1.68^ns	3	0.14^ns	2	1.29^ns	3	0.23^ns
误差 Error	24		24		16		36

Fig. 4 Variations of net photosynthetic rate (Pn) of distal ramets (A) and proximal ramets (B) with time (mean ± SE). ◆, ■, ▲ and × represent stolon connections are severed and distal ramets are assigned to Cd 2+ stressed soil, stolon connections left intact and distal ramets are assigned to Cd2+ stressed soil, stolon connections are severed and distal ramets are assigned to normal soil, and stolon connections are left intact and distal ramets are assigned to normal soil treatments, respectively.

Fig. 5 Variations of maximum quantum yields of photosystem II (A) and chlorophyll contents (B) of distal ramets with time (mean ± SE). ◆, ■, ▲ and × represent stolon connections are severed and distal ramets are assigned to Cd 2+ stressed soil, stolon connections left intact and distal ramets are assigned to Cd2+ stressed soil, stolon connections are severed and distal ramets are assigned to normal soil, and stolon connections are left intact and distal ramets are assigned to normal soil treatments, respectively. Data on maximum quantum yields of photosystem II in distal ramets is not available at sixth week.

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