Effects of environmental conditions and exogenous silicon concentration on absorption and allocation of silicon in cucumber

Objectives This experiment was conducted to study the effects of environmental conditions and silicon supplying levels on the active and passive absorption process of Si by cucumber.

Methods Using ‘Xintaimici’ cucumber as the tested material, soilless culture methods were adopted in an artificial climate chamber. Four environmental conditions were set up: 1) T1, day/night temperature 22℃/12℃, relative humidity 85%/95%, light intensity 300 μmol/(m²·s); 2) T2, day/night temperature 22℃/12℃, ralative humidity 85%/95%, light intensity 600 μmol/(m²·s); 3) T3, day/night temperature 28℃/18℃, ralative humidity 55%/65%, light intensity 300 μmol/(m²·s); 4) T4, day/night temperature 28℃/18℃, ralative humidity 55%/65%, light intensity 600 μmol/(m²·s). For the experiment of Si absorption dynamics, 10 levels were set up: 0, 0.085, 0.17, 0.34, 0.51, 0.68, 0.85, 1.02, 1.36, 1.70 mmol/L. For the experiment of Si absorption and distribution, three concentrations of 0.085, 0.17, 1.7 mmol/L were set up.

Results Among 4 environmental conditions, the silicon absorption rate and silicon content in organs were all T4>T3>T2>T1. At lower silicon concentration (0.085 and 0.17 mmol/L), the silicon absorption of cucumber was mainly active process in T1, T2 and T3, and passive process in T4; at higher silicon concentrations (1.7 mmol/L), however, passive absorption was dominant under all the four environmental conditions. At same temperature, the proportion of passive absorption under strong light was greater than that under weak light. Under the same light intensity, the proportion of passive absorption at high temperature was higher than that at low temperature. Under same environmental conditions, with the increase of the exogenous silicon concentration, both the passive absorption and total absorption of silicon in cucumber increased, and the proportion of passive absorption increased.

Conclusions Both environmental conditions and exogenous silicon concentrations affect the active and passive absorption of cucumber to silicon, high temperature, strong light and high silicon concentration increase the proportion of passive absorption.