Dual response to nutrients in Sorghum bicolor: The role of critical periods in expression of adaptive plasticity

Abstract

The growth response of Sorghum bicolor was followed for 34 days for plants exposed to modified nutrient concentrations from day 8 (early-treated) and from day 12 (late-treated) following imbibition. In late-treated plants, the effect of nutrient starvation on growth rate increased with time. In contrast, the influence of nutrient starvation was not cumulative in early-treated plants, and the rate of growth was stabilized (with regard to plants growing in a standard medium) after about ten days of treatment. This suggests an adaptive adjustment of early-treated plants to low-nutrient concentration. Differences between early and late-treated plants suggest that expression of this adaptive response is possible only during a critical period in development, the same already identified for salt-adaptation in Sorghum. A similar relationship between shoot weight and blade length was observed for all the early-treated plants. This contrasts with the two relationships noticed for late-treated plants exposed to simi...