Ecological significance of fruit heteromorphism in the annual ephemeral Senecio subdentatus

doi:10.3724/SP.J.1258.2011.00663

Abstract

Abstract:

Aims Senecio subdentatus (Asteraceae) is an annual ephemeral in the Gurbantunggut Desert, northern Xinjiang, China. It produces two morphs of achenes in the same infructescence. Our aim was to determine the morphological, dispersal and germination characteristics of the heteromorphic achenes and the relationship between size and yield of plants produced by them.

Methods Shape, size, surface ornamentation (via SEM micrographs), dispersal, germination of the two morphs of achenes, number of peripheral and central achenes per infructescence and per plant and plant biomass were determined in the laboratory. The mode and duration of achene dispersal were measured in the field.

Important findings The peripheral and central achenes are columnar, but they are significantly different in size, color, length of pappus and pericarp micro-morphology. Peripheral achenes are pale yellow and central ones brown. There are no differences in rate of descent in still air or dispersal distance at wind speeds of either 1 or 2 m·s^-1. Therefore, the dispersal ability of the two achene morphs was not significantly affected by achene size or length of pappus. The germination percentages were higher for 1-month old peripheral achenes at 5/2, 15/2, 20/10, 25/15 and 30/15 °C, and there were significant differences among temperatures in both achene morphs. Light did not affect germination significantly. There are more peripheral than central achenes in a capitulum. The proportion of peripheral achenes in an individual was negatively correlated with plant size, while the proportion of central achenes was positively correlated with plant size. This suggests that small plants produce more peripheral achenes with higher germination percentages, while large plants produce more central achenes with lower germination percentages. In the unpredictable environment of the Gurbantunggut Desert, plant size of S. subdentatus is closely related to micro-habitat. This species can reduce competition among siblings and increase adaptive responses to different micro-environmental conditions by making full use of germination differences between peripheral and central achenes and regulating yield of both achenes in different plant sizes.

Key words: achene yield, annual ephemeral, dispersal, ecological adaptations, germination, fruit heteromorphism, morphology characteristics, Senecio subdentatus

JANNATHAN Mamut, TAN Dun-Yan, CHENG Xiao-Jun. Ecological significance of fruit heteromorphism in the annual ephemeral Senecio subdentatus[J]. Chin J Plant Ecol, 2011, 35(6): 663-671.

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Figures/Tables 4

References 52

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观测指标 Parameter	外围果 Peripheral achenes	中央果 Central achenes	F	p
形状 Shape	柱形, 近直立 Columnar and approximately straight	柱形, 近直立 Columnar and approximately straight	-	-
颜色 Colour	淡黄色 Pale yellow	褐色 Brown	-	-
果体长 Length of achene (mm)	5.36 ± 0.08^a	4.99 ± 0.09^b	10.05	< 0.01
果体宽 Width of achene (mm)	0.39 ± 0.01^a	0.31 ± 0.01^b	22.73	< 0.01
冠毛数量(个) No. of pappi	175.80 ± 5.53^a	164.80 ± 4.31^a	10.66	0.12
冠毛长 Length of pappi (mm)	5.26 ± 0.16^a	4.67 ± 0.05^b	14.60	< 0.01
果实百粒重 Mass per 100 achenes (mg)	0.44 ± 0.00^a	0.38 ± 0.00^b	27.95	< 0.01
胚百粒重 Mass per 100 embryos (mg)	0.19 ± 0.00^a	0.18 ± 0.00^a	0.19	0.67

观测指标 Parameter	外围果 Peripheral achenes	中央果 Central achenes	F	p
形状 Shape	柱形, 近直立 Columnar and approximately straight	柱形, 近直立 Columnar and approximately straight	-	-
颜色 Colour	淡黄色 Pale yellow	褐色 Brown	-	-
果体长 Length of achene (mm)	5.36 ± 0.08^a	4.99 ± 0.09^b	10.05	< 0.01
果体宽 Width of achene (mm)	0.39 ± 0.01^a	0.31 ± 0.01^b	22.73	< 0.01
冠毛数量(个) No. of pappi	175.80 ± 5.53^a	164.80 ± 4.31^a	10.66	0.12
冠毛长 Length of pappi (mm)	5.26 ± 0.16^a	4.67 ± 0.05^b	14.60	< 0.01
果实百粒重 Mass per 100 achenes (mg)	0.44 ± 0.00^a	0.38 ± 0.00^b	27.95	< 0.01
胚百粒重 Mass per 100 embryos (mg)	0.19 ± 0.00^a	0.18 ± 0.00^a	0.19	0.67