50 Years Ago

摘要

Despite some impressive demonstrations of root-pressure, 'pumping' or positive pressure is generally thought to be of little importance for the ascent of sap in trees... In ten species of palms at Calcutta I was able to detect and measure positive root-pressures throughout the year, sometimes enough to lift sap to heights exceeding that of the trees... The positive pressure exceeds the negative pressure considerably. It often exceeds the plant's needs... The distal part of a cut root of a fruited banana plant was seen to develop pressure.