Chin J Plan Ecolo ›› 2006, Vol. 30 ›› Issue (6): 998-1004.doi: 10.17521/cjpe.2006.0128
• Research Articles •
ZU Yuan_Gang; ZHANG Zhong_Hua; WANG Wen_Jie; YANG Feng_Jian; HE Hai_Sheng
Background and Aims Mikania micranth is a well-known invasive species. Study of its characteristics will increase our knowledge of invasive mechanisms and management of invasive species. Photosynthesis of leaves is one of the invasive characteristics of M. micranth, but no studies have focused on assimilation characteristics of its stems. Methods We compared young green stems and mature leaves using the LI_64 00 gas exchange and fluorescence system, as well as laser scanning confocal microscopy to observe the distribution of chlorophyll.
Key Results Electron transport rate (ETR) and actual photochemical efficiency of system Ⅱ (ΦPSⅡ) of stems and leaves were positively correlated (0 .97), suggesting similar photosynthetic structure in stems and leaves. The gas exchange rate under constant conditions was stable for leaves but fluctuating for stems, possibly because of the pore factor of stems. Under the same area and saturated light (PPFD=2 000μmol·m－2·s－1), theETR of leaves was 42 .44 and the ETR of stems was 30.32μmol·m－2·s－1. However, under the same area and low light (PPFD=10μmol·m－2·s－1), the ΦPSⅡ of leaves was 0.69 and theΦPSⅡ of stems was 0.57. The electron transport rate in stems was 4.24 per unit SPAD, 2.3 times that of leaves. Actual photochemical efficiency of system Ⅱ was 0.08 per unit SPAD, 3 times that of leaves. Our research also indicated that light adaptive ability was better in stems than in leaves. Chlorophyll existed mainly in two tissues: cortex and around vascular bundles. It is possible that there are different chlorophyll functions in different tissues.
Conclusions This study indicates that photosynthesis occurred in young green stems of M. micrantha and the instantaneous efficiency of light utilization in stems was higher than in leaves. Results were unclear regarding the function of chlorophyll in different tissues.
ZU Yuan-Gang, ZHANG Zhong-Hua, WANG Wen-Jie, YANG Feng-Jian, HE Hai-Sheng. DIFFERENT CHARACTERISTICS OF PHOTOSYNTHESIS IN STEMS AND LEAVES OF MIKANIA MICRANTH[J].Chin J Plan Ecolo, 2006, 30(6): 998-1004.
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