“…The circadian rhythm, an endogenous rhythm observed in plants, has been studied extensively in relation to plant shoot growth (Walter et al, 2009). Daily rhythmic patterns for plant root growth parameters have also been found with respect to various physiological phenomena such as nitrate uptake (Pearson and Steer, 1977), root respiration (Hansen, 1980), xylem sap exudation (Vaadia, 1960), hydraulic conductivity, root pressure (Henzler et al, 1999), water uptake (Nakanishi et al, 2001), and mucilage exudation (Iijima et al, 2003c). Recently, a diurnal growth pattern of root elongation was reported in Arabidopsis thaliana , although the endogenous rhythmicity itself was not analyzed.…”