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Silica content, anatomical traits and herbivory damage in leaves with different age and solar radiation exposition of invasive tree Ligustrum lucidum.
Conferencia; 7th International Conference on Silicon in Agriculture,; 2017
Ligustrum lucidum (Aiton) is an invasive tree out of its native distribution range (China). In Argentina, many areas have been invaded by this species, resulting in significant changes in the dynamics and functionality of the ecosystems. Previous studies have detected the herbivory preference in individuals developed in different environments. In addition, there are antecedents about the presence of amorphous silica biomineralizations in this species. However, little is known about how silica accumulation occurs and if it content have effect in the leaves palatability. Considering the scarce information about silicification process in Ligustrum lucidum, and its possible influence in its susceptibility to herbivory damage, we carried on this work. The aims were 1) to analyze the silica content in leaves with different size (age) and solar exposition, and 2) to relate this silica content with anatomical features and herbivory damage, in tress from forests from SE Pampean region, Argentina. We selected 5 individuals with similar height. In each plant, 5 sun-exposed and 5 shadow leaves with 3 different age or size (new/small, media/median and old/big) were collected. Leaves were scanned, dried at 60 C for five days and weighted in order to estimate specific leaf area. Damage produced by herbivores in the field per leaf was measured by the proportion of leaf surface eaten calculated using Image J version 1.42d (National Institute of Health, Bethesda, Md, USA). Silica content was quantified through a calcination technique (Labouriau, 1983) and through a dissolution technique with Na2CO3 digestion. Some samples were subjected to histological techniques (cross sectioning, clearing and staining). Data was subjected to Kruskal-Wallis or ANOVA tests. Silica content ranged between 0.7-4% (calculated as % dry weight), and was higher in older leaves (F=30.55, p< 0.01). Shadow leaves have higher silica content, higher SLA, and, in general, a lower herbivory damage in comparison to sun leaves. A higher SLA in shadow leaves is related to anatomical characteristics, such as a thinner parenchyma. These results showed that silica content increase with age, due to the continuous silica accumulation along the life of the organs. A higher accumulation of silica in shadow leaves could be related to a long life span of this type of leaves. Finally, the higher accumulation of silica in shadow leaves, along with a lower disponibility of biomass (due to thinner leaves) could account to a lower herbivory damage.