Einfluss von Wurzelraumtemperatur und Wachstumsbedingtem Wasserbedarf auf die Hydraulische Leitfähigkeit von Maiswurzeln

Abstract

Low root zone temperatures (RZT) decrease the hydraulic conductivity of roots (Lp), and thus, may affect shoot growth by insufficient water supply. In the present experiments with maize (Zea mays L.), Lp was compared after short-term (4 h) and long-term (4–5 d) treatment with low RZT (12°C) to examine if maize roots can adapt to low temperatures by increasing their Lp. At 12°C RZT, the shoot growth rate was varied, by growing the plants with their shoot base including the apical meristem either at 12°C or 24°C.

In the short term, Lp was decreased at 12°C RZT to 25% of Lp at 24°C, independently of the shoot base temperature (SBT). When the roots were rewarmed to 24°C, Lp completely recovered to the values of plants which were continuously grown at 24°C RZT. In the long term, the rate of water flux through the roots at 12°C was increased by factor 2, when the SBT was increased from 12°C to 24°C. In these plants grown at 12°C RZT and 24°C SBT, Lp increased with time, but remained substantially lower than Lp of plants which were continuously grown at 24°C RZT, even when the temperature during the measurement of Lp was increased to 24°C. This indicates that the low Lp after long term treatment at 12°C is associated with structural modifications of root characteristics which influence Lp (e.g. membrane composition, suberinization, decrease in the number of lateral roots). In plants grown at 12°C RZT and 12°C SBT no increase in Lp with time was measurable, indicating that the adaptational response of the plants grown at 24°C SBT was induced by the increase in the growth-related water demand and not by the temperature perse.