CALCIUM ACCUMULATION, CALCIUM DISTRIBUTION, AND BIOMASS PARTITIONING IN COLLARDS

'Vates' collard (Brassica oleracea L. Acephala Group) was more susceptible to tipburn than 'Blue Max' or 'Heavi Crop' in field and nutrient solution culture experiments. The root system of 'Vates' was smaller than that of 'Blue Max' in all experiments. Because of its smaller root system, 'Vates' may be more susceptible to moisture stress than 'Blue Max' when grown under high-temperature conditions on sandy soils, thus increasing susceptibility to tipburn. Root system size, however, did not influence Ca accumulation or Ca concentration in the plants. Calcium accumulation rate was higher for 'Blue Max' and 'Heavi Crop' than for 'Vates' during the 3rd through the 5th weeks of culture in a nutrient solution that contained 5 mM Ca. Calcium efficiency ratio (CaER, milligrams of dry matter produced per milligram of Ca in tissue) for young leaves was higher for 'Blue Max' and 'Heavi Crop' than for 'Vates' when plants were grown with 1 mM Ca, which may partly explain the greater susceptibility of 'Vates' to tipburn. 'Heavi Crop' had a higher total plant CaER than 'Blue Max' when grown with 5 mM Ca.