Time‐course of uptake of dissolved inorganic carbon through willow roots in light and in darkness

Abstract

Uptake of dissolved inorganic carbon (DIC) from a nutrient solution by willow roots was measured in light and darkness and the distribution in the plant of DIC taken up by the roots was determined. It was also studied whether the transport system could be activated by preincubation with dissolved inorganic carbon. Willow plants (Salix cv. Aquatica gigantea) grown in hydroponic culture media were preincubated for 2 days with or without 0.74 mM NaHCO3. After preincubation, either unlabelled or [14C]‐labelled NaHCO3 was injected into the media and after 1, 5, 10 and 24 h either in light or in darkness the plants were harvested in pieces into liquid nitrogen, lyophilized and burned in a combustion chamber. 14C was transported through the roots to the shoots and leaves both in light and in darkness, although incorporation of 14C in darkness was only half of that in light at the end of the 24‐h feeding period. Both in light and in darkness the amount of 14C increased in all parts of willow plants with time. In light the rate of labelling was highest into cuttings and shoots. In darkness more than half of the total label was detected in cuttings of both the non‐activated and the activated treatments. In the shoots the middle part was most strongly labelled after 5 and 10 h, but after 24 h 14C moved towards the base of the shoot. In the leaves at all feeding times most radioactivity was incorporated into the young, fully open leaves on the upper part of the shoots. Preincubation of plants with unlabelled NaHCO3 in growth media had no clear effect on the rate of DIC uptake either in light or in darkness.

Advantages of compound‐specific stable isotope measurements over bulk measurements in studies on plant uptake of intact amino acids

“…35 Vuorinen et al 36 have shown that this bicarbonate can be taken up by plant roots and thereafter be incorporated into root biomass via the phosphoenolpyruvate carboxylase (PEP) pathway (dark fixation). In addition to other abiotic and biotic factors, the activity of PEP has been shown to be mainly controlled by the amount of mineral N uptake.…”

Relative Importance of Atmospheric and Root Uptake Pathways for 14CO2 Transfer from Contaminated Soil to Plants

“…Perhaps only 1 to 2% is absorbed directly through the roots (Vuorinen et al 1989;Sheppard et al 1991) although this pathway can be quite important for plants where foliar absorption is small (Keeley et al 1984). The mechanisms for upward C 0 2 transport within stems have been established for some plants, such as rice (Higuchi 1982;Higuchi et al 1984).…”

“…These equations also assume that T = 300 K and P = 100 kPa. Vuorinen et al ( 1989) estimate that direct root uptake of carbon may be 1 to 2% of the carbon assimilated by leaves. Similarly, Sheppard et al ( 199 1 ) estimate that about 1.7% of the plant carbon may be derived directly from root uptake in a carbonated soil.…”

Introduction to Phytoremediation of Contaminated Groundwater

“…In these plants, even though the majority of the CO 2 is derived from the atmosphere, between 1% and 2% of the carbon taken in by leaves is taken in by the roots (Vuorinen et al 1989). Willows represent a phreatophyte that can be planted at a contaminated site where groundwater contains low DO and high CO 2 .…”