Density-dependent regulation of above- and below-ground modules in Allium cepa var. proliferum populations

doi:10.3724/SP.J.1258.2011.00284

Abstract

Abstract:

Aims Although the relationship between size and density is central to plant ecology, research has focused on the above-ground parts of plants and few studies have examined size-density relationships of below-ground modules. Density-dependent regulation in plants can be viewed not only at population and individual levels, but also at plant part level, since growth in plants is a modular process. Our aims were to (1) investigate size-density relationships at plant part level and at individual plant level for both below- and above-ground parts of plants and (2) compare size-density relationships at the levels of plant parts and individuals.
Methods Allium cepa var. proliferum was planted in a completely random design at five plant densities (36, 49, 64, 121 and 225 plants·m^-2) and three replicates. Plot size was 5 m × 5 m. At harvest time (July 11), ten plants from each plot were destructively sampled to measure plant height, number of leaves, length of leaf blade, bulb diameter and mean weight per tiller. Each plant was separated into root, bulb, sheath and leaf blade, oven-dried for 120 h at 80 ℃, and then weighed. Regression analysis was conducted to explore the relationship between the characters measured and plant density and the allometric relationships of mean masses of below- and above-ground modules with density at plant part level and individual level.
Important findings Relationships between plant density and dry weight of root, bulb, leaf blade and sheath showed negative power functions with different allometric exponents for different plant modules: bulb (-1.14) < leaf blade (-1.03) < root (-0.78) < sheath (-0.49). Masses of below- and above-ground dry matter, as well as the whole plant, were decreased significantly with increased plant density. The allometric exponents were -1.13, -0.95 and -0.98 for below-ground, above-ground and individual plant dry matter, respectively. We concluded that the effect of density-dependent regulation on below-ground modules may be greater than that on above-ground modules. Blow-ground parts may be more closely constrained by plant density in contrast to above-ground parts and the whole plant. Consequently, competition for below-ground resources is predominant in the A. cepa var. proliferum populations.

Key words: allometry, biomass, bulb, competition-density effect, density-dependence, module, size-density relationship

LI Lei, ZHOU Dao-Wei. Density-dependent regulation of above- and below-ground modules in Allium cepa var. proliferum populations[J]. Chin J Plant Ecol, 2011, 35(3): 284-293.

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Figures/Tables 5

References 43

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x	y	方程 Equation	参数 Parameter		r	p
x	y	方程 Equation	a	b	r	p
密度 Density	株高 Plant height	L	35.72	0.06	0.85	<0.001
	叶片长 Leaf blade length	L	17.05	0.03	0.92	<0.001
	叶片数 Number of leaves	L	38.34	-0.37	-0.96	<0.001
	鳞茎直径 Bulb diameter	L	6.95	-0.01	-0.84	<0.001
	分蘖数 Number of tillers	L	11.67	-0.01	-0.24	0.40
	分蘖重 Weight per tiller	P	70.65	-0.98	-0.99	<0.001
	根生物量 Root biomass	P	22.14	-0.78	-0.98	<0.001
	鳞茎生物量 Bulb biomass	P	1 766.50	-1.14	-0.98	<0.001
	鞘生物量 Sheath biomass	P	12.50	-0.49	-0.92	<0.001
	叶片生物量 Leaf blade biomass	P	642.22	-1.03	-0.99	<0.001
	地下生物量 Below-ground biomass	P	1 855.60	-1.13	-0.97	<0.001
	个体生物量 Individual biomass	P	1 517.60	-0.98	-0.99	<0.001
	地上生物量 Above-ground biomass	P	608.47	-0.95	-0.99	<0.001

x	y	方程 Equation	参数 Parameter		r	p
x	y	方程 Equation	a	b	r	p
密度 Density	株高 Plant height	L	35.72	0.06	0.85	<0.001
	叶片长 Leaf blade length	L	17.05	0.03	0.92	<0.001
	叶片数 Number of leaves	L	38.34	-0.37	-0.96	<0.001
	鳞茎直径 Bulb diameter	L	6.95	-0.01	-0.84	<0.001
	分蘖数 Number of tillers	L	11.67	-0.01	-0.24	0.40
	分蘖重 Weight per tiller	P	70.65	-0.98	-0.99	<0.001
	根生物量 Root biomass	P	22.14	-0.78	-0.98	<0.001
	鳞茎生物量 Bulb biomass	P	1 766.50	-1.14	-0.98	<0.001
	鞘生物量 Sheath biomass	P	12.50	-0.49	-0.92	<0.001
	叶片生物量 Leaf blade biomass	P	642.22	-1.03	-0.99	<0.001
	地下生物量 Below-ground biomass	P	1 855.60	-1.13	-0.97	<0.001
	个体生物量 Individual biomass	P	1 517.60	-0.98	-0.99	<0.001
	地上生物量 Above-ground biomass	P	608.47	-0.95	-0.99	<0.001

因变量 Dependent variable	自变量 Independent variable	分析类型 Analysis type	F	p	R²
根生物量 Root biomass	密度 Density	方差分析 ANOVA	19.4	<0.001
	密度 Density	协方差分析 ANCOVA	4.4	0.031	0.86
	个体生物量 Individual biomass	协方差分析 ANCOVA	2.3	0.161	0.86
鳞茎生物量 Bulb biomass	密度 Density	方差分析 ANOVA	2 651.7	<0.001
	密度 Density	协方差分析 ANCOVA	82.8	<0.001	1.000
	个体生物量 Individual biomass	协方差分析 ANCOVA	45.4	<0.001	1.000
鞘生物量 Sheath biomass	密度 Density	方差分析 ANOVA	18.3	<0.001
	密度 Density	协方差分析 ANCOVA	0.6	0.696	0.833
	个体生物量 Individual biomass	协方差分析 ANCOVA	1.1	0.326	0.833
叶片生物量 Leaf blade biomass	密度 Density	方差分析 ANOVA	302.3	<0.001
	密度 Density	协方差分析 ANCOVA	16.8	<0.001	0.989
	个体生物量 Individual biomass	协方差分析 ANCOVA	1.1	0.326	0.989
个体生物量 Individual biomass	密度 Density	方差分析 ANOVA	3 241.3	<0.001	0.996
地上生物量 Above-ground biomass	密度 Density	方差分析 ANOVA	2 386.7	<0.001
	密度 Density	协方差分析 ANCOVA	77.5	<0.001	0.998
	个体生物量 Individual biomass		0.1	0.725
地下生物量 Below-ground biomass	密度 Density	方差分析 ANOVA	1 795.1	<0.001
	密度 Density	协方差分析 ANCOVA	77.4	<0.001	1.000
	个体生物量 Individual biomass		95.7	<0.001

因变量 Dependent variable	自变量 Independent variable	分析类型 Analysis type	F	p	R²
根生物量 Root biomass	密度 Density	方差分析 ANOVA	19.4	<0.001
	密度 Density	协方差分析 ANCOVA	4.4	0.031	0.86
	个体生物量 Individual biomass	协方差分析 ANCOVA	2.3	0.161	0.86
鳞茎生物量 Bulb biomass	密度 Density	方差分析 ANOVA	2 651.7	<0.001
	密度 Density	协方差分析 ANCOVA	82.8	<0.001	1.000
	个体生物量 Individual biomass	协方差分析 ANCOVA	45.4	<0.001	1.000
鞘生物量 Sheath biomass	密度 Density	方差分析 ANOVA	18.3	<0.001
	密度 Density	协方差分析 ANCOVA	0.6	0.696	0.833
	个体生物量 Individual biomass	协方差分析 ANCOVA	1.1	0.326	0.833
叶片生物量 Leaf blade biomass	密度 Density	方差分析 ANOVA	302.3	<0.001
	密度 Density	协方差分析 ANCOVA	16.8	<0.001	0.989
	个体生物量 Individual biomass	协方差分析 ANCOVA	1.1	0.326	0.989
个体生物量 Individual biomass	密度 Density	方差分析 ANOVA	3 241.3	<0.001	0.996
地上生物量 Above-ground biomass	密度 Density	方差分析 ANOVA	2 386.7	<0.001
	密度 Density	协方差分析 ANCOVA	77.5	<0.001	0.998
	个体生物量 Individual biomass		0.1	0.725
地下生物量 Below-ground biomass	密度 Density	方差分析 ANOVA	1 795.1	<0.001
	密度 Density	协方差分析 ANCOVA	77.4	<0.001	1.000
	个体生物量 Individual biomass		95.7	<0.001