Effects of water and nutrient stresses on reduction of vegetative growth in chrysanthemum grown under restricted root zone volume

Two experiments were conducted to test the effects of reducing water and nutrient stresses on vegetative growth of chrysanthemum cv. Pinky in restricted root zone volume (10∼1000 ml). In Exp. 1, plants were grown using continuous flowing hydroponic system (CFHS). In Exp. 2, plants grown on a substrate were supplied nutrient solution via a drip system (SDS) 1, 3, 8 or 13 times per day until leaching occurred. In CFHS, stem length and node number were unaffected by root zone volume 25 days after planting (DAP). Total leaf area, shoot and root dry weights decreased with a decrease in root zone volume; there were small differences among the plants grown in different containers, e.g. shoot dry weight of plants grown in 10 ml containers was about 80% of that in 1000 ml containers. Shoot to root ratio slightly increased with a decrease in root zone volume. In SDS, reduction in stem elongation was observed 14 DAP in plants grown in 30 ml containers fertigated only once a day. However, there was little difference in stem lengths among the plants grown in different containers 28 DAP when fertigated 8 times per day. Shoot growth 35 DAP was reduced with a decrease in root zone volume, however in plants grown in 30 ml or 100 ml containers, reduction of shoot growth markedly decreased with an increase in fertigation frequency. Root zone volume had a little effect on shoot growth if plants were fertigated 8 or 13 times. Irrespective of fertigation frequency, root dry weight increased with an increase in root zone volume. Shoot to root ratio was unaffected by root zone volume in plants fertigated 1 or 3 times but the ratio in plants treated 8 or 13 times increased with decrease in root zone volume. Thus, limiting of water and nutrients is the main factor in growth suppression caused by root zone restriction. Hence, vegetative growth of chrysanthemum plants in small container (≤ 100 ml), e.g. cell or pot transplants production, can be sustained by the application of water and nutrients 8 times per day.