Rapid acclimation of root hydraulic conductivity to low temperature

Abstract

Abstract induced by increased resistance to water uptake or fluxin the roots at low temperature (Anderson andRoot hydraulic conductance of many species is sub-McNaughton, 1973; Babalola et al., 1968; Bohning andstantially reduced by exposure to low temperatures.Lusanandana, 1951; Kramer, 1942; McWilliam et al.,The objective of this research was to investigate thedecrease and recovery of root hydraulic conductivity 1982). This can be a problem in greenhouses when coldin spinach (Spinacia oleracea L.) root systems upon water is applied to rapidly transpiring plants. Leavesexposure to low temperature. Root hydraulic conduc- quickly wilt and can suVer injury. Root zone temperaturetivity (Lp) was determined for detached whole root is also important in field agriculture (Sharif Zia et al.,systems as the slope of the flux and an applied pres- 1994; Wraith and Ferguson, 1994). Low soil temperaturesure gradient. Water flux (Jv), of root systems grown limits spring transplanting and seeding and productivityat 20°C, decreased immediately upon exposure to of many plants. Although soil temperatures do not fluc-5°C. After 2–5 h Jv recovered and reached a stable tuate as rapidly as air temperatures, soil surface temper-value after 12 h exposure to 5°C. In separate experi- ature experiences diurnal temperature excursions, as wellments, the root Lp of plants acclimated for 7 d at 5°C as significant changes due to changes in season andwas 125% greater than that of isolated root systems weather. Leaf and bud acclimation to temperature is wellacclimated for 12 h at 5°C. Lp of plants grown and known, however, there is little information about themeasured at 5°C was about 50% of the Lp of plants ability of root systems to acclimate to temperature fluctu-grown and measured at 20°C. The rapid acclimation ations. The present study was undertaken to determineto low temperatures observed in detopped root sys- the ability and speed that spinach (Spinacia oleracea L.)tems was also indicated in intact plants at 20/5°C root systems can acclimate to low temperatures. Spinach(shoot/root temperatures) using mass flow porometry. was chosen for this study as it is frequently grown in theAcclimation of the root system after exposure to 5°C autumn, winter or early spring in diVerent regions of thewas apparent by recovery of stomatal opening. These country and may encounter a variety of soil and airresults indicate that spinach root systems have the temperatures.ability to acclimate rapidly to changes in temperatureand to continue acclimating during prolonged expo-sure to low temperature.