Internal tipburn of cabbage (Brassica oleracea var. capitata)

Internal tipburn of cabbage (Brassica oleracea var. capitata) is a serious quality defect. The discolouring and desiccation of inner head leaves may r ender whole yields useless. The disorder is regarded as a localized calcium deficiency. The deficiency is not caused by reduced calcium availability t o the plant, but rather by calcium transport characteristics within the pla nt. Because of the absence of transpiration from the inner head leaves of t he cabbage plant, calcium is transported to the meristematic tissues in the head mainly by root pressure flow or because of meristematic sink activity during the night. High growth rates are known to increase the incidence of internal tipburn. Probably because of the increased demand for calcium per unit of time, the result of disruption in the calcium transport to the hea d is more serious. Conditions of even transpiration between day and night, whether high or low, reduce root pressure flow to the head and thereby may induce development of internal tipburn. A combination of high growth rates and low root pressure flow during periods of prolonged dry, sunny weather w ith high transpiration rates during the day as well as during the night, ma y be especially important in inducing internal tipburn, because of insuffic ient calcium influx in the cabbage head under such conditions. As initiatio n of calcium deficiency in growing tissue is a subcellular process, visible symptoms of internal tipburn may be expressed only later. Growers are prim arily advised to cultivate internal tipburn resistant cultivars. Recommenda tions to limit the occurrence of internal tipburn are formulated.