Diurnal uptake of nitrate and potassium during the vegetative growth of tomato plants

Abstract

Tomato plants (Lycopersicon esculentum Mill.) of the F 1 hybrid variety Turbo were grown in a NFT system for 22 days. On days 16 and 20-22 inclusive of the experiment, the diurnal variation in nitrate (NO 3 ), potassium (K), and water uptake rates were measured. Nitrate and K uptake rates were subject to large diurnal variation with maximum uptake rates occurring during the day period. Two peaks of diurnal uptake rates were identified, one large peak during the day period and a second much smaller one during the first 2-4 hours of the night. Under the conditions of the experiment, night nutrition made up 35 to 40% of the total daily uptake of K and NO 3 . Water uptake rates followed a diurnal oscillation with a single peak pattern. Highest rates occurred at the middle of the photoperiod and lowest rates were measured at night. Over the entire day and night cycle there was no correlation between the rates of water and nutrient uptake. This may be of importance in the fertilization of hydroponically grown plants since in horticultural practice nutrients and water are supplied together in quantities large enough to meet plant water demand but not nutrient requirements. INTRODUCTIONCurrent knowledge of diurnal variation in nutrient uptake by plants is still very sketchy. Studies on diurnal uptake of K and NO3 have been made on monocotyledons (3,6,12,15,16,19) but are rare for dicotyledons in particular for tomato. Several authors have described a simple pattern of NO3 and K uptake with highest uptake rates reached during the day period followed by a constant decline 1. Present address: INRA, Station d'Agronomie, DomaineSaint-Paul, 84140 Montfavet FRANCE.

Regulation of Root Ion Transporters by Photosynthesis: Functional Importance and Relation with Hexokinase

“…Finally, induction by sugars also was found for genes that encode transporters for ions that are not incorporated in amino acids (Pi) or not even metabolized (K ϩ ). This finding suggests a more general control, not restricted to amino acid synthesis, that is in agreement with the fact that the light/dark transition affects the root uptake of many ions (Clément et al, 1978;Smith and Cheema, 1985;Hatch et al, 1986;Le Bot and Kirkby, 1992;Delhon et al, 1995a). In shoots, light and/or sugars also regulate the expression of K ϩ channel genes (Deeken et al, 2000;Ache et al, 2001;Moshelion et al, 2002) in addition to NH 4 ϩ transporter genes (von Wirén et al, 2000b).…”

“…However, a more general control over ion uptake also has been documented that coordinates the activity of root transport systems with the photosynthetic activity of the shoot (Forde, 2002). Uptake rates of many ions are dependent on light conditions and fluctuate diurnally (Clément et al, 1978;Smith and Cheema, 1985;Hatch et al, 1986;Le Bot and Kirkby, 1992;Delhon et al, 1995a) or are stimulated by an increase in light intensity (Gastal and Saugier, 1989).…”

PGP4, an ATP Binding Cassette P-Glycoprotein, Catalyzes Auxin Transport in Arabidopsis thaliana Roots

“…This makes sense, as a symporter such as AUX1 would be expected to be more sensitive to changes in pH associated with root gravistimulation (Hou et al, 2004). The amelioration of pgp4 growth phenotypes by increased light and sucrose also supports this relationship, as light and sucrose enhance ATP-driven proton extrusion (Le Bot and Kirkby, 1992;Stewart and Lieffers, 1994) and, thus, chemiosmotically driven transport in roots (Li et al, 2005). Proteins were photoaffinity-labeled with UV irradiation after removal of unbound ligands and analyzed by SDS-PAGE.…”

“…This proved to be the case (data not shown). Higher light conditions have been shown to increase both sucrose production and apoplastic acidification in roots (Le Bot and Kirkby, 1992;Stewart and Lieffers, 1994). Lower apoplastic pH was recently shown to increase chemiosmotically driven auxin efflux and uptake in Arabidopsis roots (Li et al, 2005).…”

A Simple Method for Quantitative Estimation of Rhizosphere pH along Root Axes through Visualization

“…These studies suggested that the light conditions given to the shoot affected the rhizosphere pH. Also, uptake rates of different forms of nitrogen vary greatly with the light condition given to the shoot (Keltjens and Nijestein, 1987;Le Bot and Kirkby, 1992;Delhon et al, 1995;Qurry et al, 1996;Macduff et al, 1997). Our main aim here is to evaluate the effects of light conditions given to the shoot on the rhizosphere pH.…”