Restricted Root Zone Volume: Influence on Growth and Development of Tomato

Abstract

‘Better Bush’ tomato ( Lycopersicon esculentum Mill.) plants were grown in small- (450-cm 3 ) or large-(13,500-cm 3 ) volume plastic containers and harvested every 2 weeks from time of planting until 12 weeks, at which time ripe fruits had developed. Plants were fertilized three to six times daily to prevent drought and nutrient stress. After only 2 weeks, there were significant reductions in total height, node number, leaf area, and dry weight of leaves. By 4 weeks, dry weights of stems and roots were also significantly less in small pots than in large pots. These differences were maintained for the next 10 weeks. Root restriction also generally caused an increase in root : shoot ratio. Roots in small-volume containers formed a highly branched mat, whereas those in large-volume containers had long taproots and showed little branching. Root restriction also significantly reduced the total number and fresh and dry weight of mature fruits. Despite these differences, both groups of plants had nearly 41% of the total photosynthate in the reproductive portion of the plant after 12 weeks of treatment. During weeks 6–8, the mean relative growth rate of plants in small pots was twice that in large pots but thereafter was only half as much. Restricting root volume had little or no effect on net assimilation rate. These data suggest that, for a given growing area, a culture system using small containers would be more efficient in producing fruit for a given weight and size of plant than one using large containers. These findings have important implications for growers and researchers involved in growing plants in confined spaces such as in a phytotron or controlled ecological life support system (CELSS).