Do the nutrition and physiology of eucalyptus seedlings respond to silicon (Si) supply?

Abstract

In Brazil, Eucalyptus plantations are found, generally in soils with naturally low chemical fertility. Silicon (Si) can improve photosynthesis, decrease plant transpiration and increase water use efficiency (WUE). This study aimed to evaluate the effect of Si supply at five rates (0, 0.25, 0.50, 0.75 and 1.00 mmol L-1) for growing Eucalyptus clone IPB8 seedlings (E. urophylla E. grandis) in Clark's nutrient solution in a greenhouse. Plant growth, nutritional status, gas exchange, leaf water potential (?w), leaf area (LA), inclination angle of leaves and stomatal density (SD) were measured. There was no significant response in Eucalyptus seedling growth due to Si application, which was related to the absence of benefits provided by Si in plant nutritional status and physiology. The efficiency of assimilation (EA), efficiency of translocation (ET) and efficiency of utilization (EU) did not show significant results either. The low ET indicates that Si was highly accumulated in the root (75.4 % in relation to total Si absorbed by plants), which may also have contributed to the lack of the benefits expected. Despite that, Si application promoted higher rates of photosynthesis when compared to plants with 0 mmol Si L-1, increasing the total dry matter production by up to 28 % at an Si rate 0.50 mmol L-1, which also provided a trend of higher growth, EU, LA and SLA, showing it to be the best rate for this Eucalyptus species.