Leea glabra is an erect shrub species with a height of 1.5–3.5 m and is one of about 70 Leea species. It is native to the southern parts of Yunnan and Guangxi Provinces of south-west China and is mainly distributed in the lower layer of forests up to 1,200 m asl. (Flora of China, eFloras.org).
Dr. Meng Lingzeng of Xishuangbanna Tropical Botanical Garden (XTBG) and his teachers dealt with the shrub Leea glabra and the defensive function of the extrafloral nectaries found at leaf petioles in relation to their interactions with ants under different conditions. They conducted field experiments with naturally grown L. glabra plants in a tropical forest plot in the Naban River Watershed National Nature Reserve within the Dai autonomous prefecture of Xishuangbanna, southern Yunnan Province, south-west China (22°10′N, 100°38′E).
Their study was aimed to answer the following major questions: (1) is the quantity of extrafloral nectary secretions and the sugar concentration of the nectar in artificially damaged young leaves higher than in old leaves? (2) Are ant abundances higher after damage on young leaves than damage on old leaves? If so, is ant recruitment related to changes in extrafloral nectary production or to the release of volatile organic compounds after artificial damage? (3) Are there differences in tannin concentrations in leaves of different ages, indicating tannins are an additional mechanism of herbivore defense?
The research results show that young leaves of L. glabra are protected against attacks by herbivores by different mechanisms which include: (1) the constitutive activity of extrafloral nectaries during the period of young leaf production, which attract ants from the surrounding ground; (2) a mechanism induced by the damage of young leaves, which leads to increased ant recruitment, most probably caused by the release of volatile organic compounds and (3) a higher allocation to tannins in young leaves than in older leaves. Young leaves of the L. glabra plants have multiple defense mechanisms, which indicate that those young tissues are of significant value to the plant.
The study entitled “Young leaf protection in the shrub Leea glabra in south-west China: the role of extrafloral nectaries and ants” has been published online in Arthropod-Plant Interactions, DOI 10.1007/s11829-011-9151-6
International cooperation project (2007DFA91660) of the Ministry of Science and Technology (MOST) of China partly funded the study.