Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (4): 681-688.DOI: 10.3773/j.issn.1005-264x.2009.04.006

Special Issue: 青藏高原植物生态学:种群生态学

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TRADE-OFF BETWEEN SIZE AND NUMBER OF CAPITULUM AND SEED IN SAUSSUREA JAPONICA: EFFECTS OF RESOURCE AVAILABILITY

WANG Yang1, DU Guo-Zhen1, GUO Shu-Qing2, ZHAO Zhi-Gang3,*()   

  1. 1Key Laboratory of Arid and Grassland Agro-ecology of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
    2Department of Chemical and Life Sciences, Hezuo National Normal Academy, Hezuo, Gansu 747000, China
    3College of Life Sciences, Wuhan University, Wuhan 430072, China
  • Received:2008-09-01 Revised:2009-03-16 Online:2009-09-01 Published:2009-07-30
  • Contact: ZHAO Zhi-Gang

Abstract:

Aims We predict that limited resources can enhance the trade-off between size and number of capitula and seeds, showing a strategy of plants. We used Saussurea japonica to investigate the relationship under different levels of light and nutrition. Our objectives are to determine 1) effects of different light and nutrition levels on characters of capitula and seeds, 2) the relationship between size and number of capitula and seeds under different light and nutrition levels and 3) whether the limitation of light and nutrition enhances the trade-off between size and quantity of capitula and seeds.
Methods We planted S. japonica in pots under four treatments: combination of two light levels (high and low) and two nutrition levels (high and low). We counted and weighed (after oven-drying at 80 °C for 72 h) capitula and seeds.
Important findings The treatments of light and nutrition had no significant effects on the number of capitula, while the effects on the mass of capitula were significant. The different treatments had significant effects on both size and number of seeds. Moreover, the relationships between size and number were influenced by different treatments of light and nutrition: under control and low nutrition level, significant positive correlations were observed between size and number for the capitula and seeds; however, significantly negative correlations between size and number were found for the capitula and seeds at the low light treatment and the low light + low nutrition treatments, exhibiting the size-number trade-off. Results suggest that environmental stress (such as low soil nutrition and limited light) enhanced the trade-off between size and number of capitula and seeds, consistent with our prediction. The trade-off can be a response of S. japonica to varied environments, which may improve the adaptability of this plant.

Key words: Saussurea japonica, size-number trade-off, reproductive strategy, environmental independence, fitness