Dependence of water conductivity on pressure and temperature in plant stems

The effects of pressure and temperature on water conductivity were examined in okra stem segments. Segments were incubated in various concentrations of sorbitol solution at various temperatures. Water was found to pass mainly through the lateral side of the segments. The shrinkage rate was found to be proportional to the difference in the water potential between the inside of the cells and the ambient solution, while the rate was inversely proportional to the viscosity of water, which is a function of temperature. The nature of the media for water conductivity was found to be consistent with Darcy’s law and with Hagen-Poiseuille’s law with a rough approximation. An attempt was made to estimate the size of the water path. Okra stem segments were incubated with and without the plant hormone auxin before transference to sorbitol solution. Shrinkage rates of segments showed that auxin caused an increase in water conductivity and thus the size of the water path.