2010 Volume 79 Issue 3 Pages 287-293
We examined the permeability of roots of Dutch ‘Dundee’ and Japanese ‘Reiyo’ varieties of tomato seedlings to nutrient solutions and potassium ions. Seedlings were grown under 5 different conditions: (1) Seedlings were grown in Otsuka-A nutrient solution adjusted to an electric conductivity (EC) of 2.4 dS·m−1, and on the experiment day their roots were permeated with EC 2.4; (2) before the experiment day the EC was changed to 7.2 dS·m−1, and then roots were permeated with EC 7.2 in the experiment; (3) roots were permeated with potassium chloride (KCl) solution whose water potential was equivalent to EC 2.4 in the experiment; (4) before the experiment day the EC was changed to EC 7.2, and then roots were permeated with KCl solution whose water potential was equivalent to EC 7.2 in the experiment; and (5) roots were permeated with that KCl solution whose water potential was equivalent to EC 7.2 in the experiment. We measured the root permeability of seedlings grown in each solution, and the water potentials of exudates by using a pressure chamber and an isopiestic psychrometer. The nutrient solution or potassium solution in the chamber was forced into the plants under pressure. We then measured the quantity of extraction from the cutting surface of the root and root surface area to calculate root permeability. As a result, we found that, except in the KCl permeability experiment with a water potential equivalent to EC 2.4, the Japanese variety had greater permeability of nutrient solution and potassium. On this basis we conjectured that the Japanese variety ‘Reiyo’, whose root permeability was high, is able to assimilate more water and nutrients than the Dutch variety ‘Dundee’. On this basis we found that differences in root permeability can be considered one reason why ‘Reiyo’ grows larger than ‘Dundee’ in the initial part of its growth period.
