Mercuric chloride effects on root water transport in aspen seedlings
HgCl2 (0.1 mM) reduced pressure-induced water flux and root hydraulic conductivity in the roots of 1-year-old aspen (Populus tremuloides Michx.) seedlings by about 50%. The inhibition was reversed with 50 mM mercaptoethanol. Mercurial treatment re- duced the activation energy of water transport in the roots from 10.82 0.700 kcal mol1 to 6.67 0.193 kcal mol1 when measured over the 4°C to 25°C temperature range. An increase in rhodamine B concentration in the xylem sap of mercury-treated roots suggested a decrease in the symplastic transport of water. However, the apoplastic pathway in both control and mercury- treated roots constituted only a small fraction of the total root water transport. Electrical conductivity and osmotic potentials of the expressed xylem sap suggested that 0.1 mM HgCl2 and temperature changes over the 4°C to 25°C range did not induce cell membrane leakage. The 0.1 mM HgCl2 solution applied as a root drench se- verely reduced stomatal conductance in intact plants, and this reduction was partly reversed by 50 mM mercaptoethanol. In ex- cised shoots, 0.1 mM HgCl2 did not affect stomatal conductance, suggesting that the signal that triggered stomatal closure originated in the roots. We suggest that mercury-sensitive processes in aspen roots play a significant role in regulating plant water balance by their effects on root hydraulic conductivity.
Wan, Xian Chong and Zwiazek, Janusz J., "Mercuric chloride effects on root water transport in aspen seedlings" (1999). Aspen Bibliography. Paper 950.