CHLORINE REQUIREMENT OF KIWIFRUIT ( ACTINIDIA DELICIOSA )

S ummary Kiwifruit ( Actinidia deliciosa var. deliciosa ) grown in solution culture have an abnormally high requirement for chlorine. A deficiency of chlorine severely restricted the growth of the shoots and roots and resulted in the development of distinctive leaf symptoms as well as unusual swellings of the tissues near the root apex. A comparatively high concentration of chloride (700 μM) was required in the nutrient solution to achieve maximum growth. The associated chloride concentration in the youngest fully expanded leaves of these plants was in excess of 60 μmol g −1 dry matter. Thus, compared to most other non‐halophytic plants, kiwifruit require over 10 times the concentration of chloride usually needed for healthy growth. The major exceptions are members of the Palmae which require similar concentrations of chloride to that of kiwifruit. Increasing the potassium status of kiwifruit plants resulted in lower chloride concentrations in the leaves. This result was not considered to be a specific physiological effect but rather the consequence of chloride along with other non‐limiting nutrients accumulating in the tissues of the severely potassium‐deficient plants. An analysis of the cation‐anion balance of the leaves suggested that the beneficial effect of chlorine on growth was unlikely to have resulted from chloride acting simply as a balancing anion. Increasing the concentration of chloride in the leaves merely led to an equivalent decrease in the concentration of nitrate‐nitrogen. Thus, the sum of the chloride plus nitrate‐nitrogen concentrations in the leaves remained relatively constant over all treatments. The results are discussed in relation to the chlorine requirements of other non‐halophytic plants.