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   Location:Home > Research > Research Progress
Induction of extrafloral nectar secretion in C. philippinum depends on leaf damage
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Update time: 2014-10-17
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Extrafloral nectaries (EFNs) of plants are considered an indirect defense against herbivores. Several studies have indicated that plants may respond differently to different herbivores. How the EFN secretion of plants reacts, however, is still an open question. It’s necessary to understand if volatile organic compounds (VOC) coming from plants damaged by different types of herbivores (e.g., specialist vs. generalist) cause the same responses in EFN secretion in nearby undamaged plants.

Dr. XU Fangfang, guided by Prof. CHEN Jin of Xishuangbanna Tropical Botanical Garden (XTBG), chose a common tropical shrub Clerodendrum philippinum to determine how extrafloral nectar secretion rate responded to herbivore type and damage type. The researchers exposed Clerodendrum philippinum to three different herbivores (one generalist locust, Atractomorpha sinensis, one specialist beetle, Hoplasoma unicolor, and one generalist weevil, Hypomeces squamosus) that feed on it in the field. Three types of mechanical damage (scratching, punching a hole in a leaf and cutting off a whole leaf).were conducted.

The researchers first asked whether there was any difference in EFN induction as a result of the feeding of different herbivores. Then, they wanted to see if the plant produced different amounts of EFN secretion in response to different types of mechanical damage. They further discussed whether VOC from a damaged plant could affect the EFN secretion a nearby intact plant. Finally, they tried to find which factor of damage affected the EFN secretion rate changed most.

In their experiment, three herbivore species showed different influences on EFN secretion. Feeding by the generalist locust which had the highest leaf consumption rate resulted in a significant increase in EFN secretion. Feeding by the other two herbivores, a specialist beetle and a generalist weevil, caused a significant increase in EFN secretion only in the high-density treatments. The significant regression of the change in EFN secretion rate on the amount of leaf area lost also indicated that leaf area lost to chewing insects may be an important factor in EFN secretion rate change.The research results suggested strongly that the induced response of EFN secretion in C. philippinum was dependent mainly on the amount of leaf area lost to chewing damage.

The study entitled “Leaf area lost, rather than herbivore type, determines the induction of extrafloral nectar secretion in a tropical plant (Clerodendrum philippinum)” has been published online in Arthropod-Plant Interactions.

 

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Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences. Menglun, Mengla, Yunnan 666303, China
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