Water Usage by Cabbage Plants at Different Stages of Growth

Cabbage plants were tested for water usage at different stages of growth under growth chamber conditions by conducting 24-h uptake studies at weekly intervals. Based on morphological development and water use, four growth stages were apparent. The stage from emergence to the start of head development was characterized by rapid growth and high transpiration rates per unit of plant material (essentially unfolded leaves). Transpiration was significantly correlated with the amount of foliage and a relatively low percentage of the moisture uptake was retained in the plant. The second, a short transitional stage, was characterized by significant increases of weight of the unfolded leaves and the start of heading. The growth rate of the leaves reached a maximum and started declining. There was also a sharp levelling off in the amount of transpiration. The third stage was characterized by early rapid expansion in size and a significant increase in weight of the head throughout the stage. With no new expanding foliage, transpiration remained static, and a higher percentage of the moisture uptake was retained. The final stage of maturity and senescence was characterized by low percentages of the moisture uptake being retained and transpiration declining because of the loss of functioning foliage.