Leaf hairiness reduces herbivory of young and mature leaves of Qualea multiflora Mart. in Brazilian Savanna

Abstract

Although all parts of the plant offer any resistance against herbivores, including trichomes and extrafloral nectaries, the herbivores are attracted to the young leaves because they have fewer secondary compounds and supporting structures. Young leaves are more palatable and their nutritional condition is increased due to the high load of some elements such as nitrogen. Qualea multiflora has characteristics such as leaf hairiness and the extrafloral nectaries (EFNs), which may reduce herbivory. The EFNs, known to attract ants, protect the plant against herbivores, increasing the reproductive fitness of the plant. The main goal here was to relate the proportion of leaf area lost to the abaxial leaf pubescence in young and mature leaves of Q. multiflora, and to verify differences in the proportion of active and inactive EFNs in young and mature leaves in this species. The study was conducted at Parque Estadual da Serra de Caldas Novas, in an area of cerrado stricto sensu, where young and mature leaves of 30 individuals were collected Q. multiflora. These leaves were measured: the proportion of area damaged by herbivores, the abaxial leaf pubescence and verified the functionality of EFNs. We tested whether the difference in the proportion of active and inactive EFNs between young and mature leaves and differences in the proportion of damaged area between young and mature leaves with active and inactive EFNs. The abaxial leaf pubescence and the proportion of damaged area in young and mature leaves were related. Although it was expected that EFNs were active more often in young leaves, significant differences were not detected. The young leaves, even with higher abaxial leaf pubescence, did not support different proportions of the area damaged by herbivores. Although no evidence of differences in the ratio of the area damaged by herbivores between young and mature leaves, in this study proved that the difference in leaf hairiness explains the variation in the proportion of damage herbivores. Since Q. multiflora had associations with other organisms that enhance their ability against herbivores, it is confirmed that its leaf hairs can also act as a barrier against leaf herbivores, although it may be the objective of further studies involving each defense strategy against damage by herbivores.