In a study, researchers conducted a meta-analysis on plant pot size. They determined that the size of the pot is a significant factor in plant growth*. The study was conducted to encourage plant researchers to carefully consider the size of pots used in experiments, as too small a pot can significantly effect results. They found that on average a doubling of the pot size resulted in increased biomass production of 43%. The results are pertinent to gardeners too, and if you are growing veggies and yield is important, carefully consider the size of your pot. The appropriate pot size will logically depend on the size of the plants growing in them, and of course attention to plant growth when seeding in trays and small pots is critical. Leave them too long and a tight ball of roots will not contribute to the future success of the plant. A large rooting volume is one of the significant benefits of the Garden Tower. Whilst the Tower comfortably holds 45-50 plants the average root volume per plant is over 3.5 litres not accounting for the intermingling of a diversity of companion plantings. This large rooting volume is of significant benefit to getting the best out of your plants.
Ref:Pot size matters: a meta-analysis of the effects of rooting volume on plant growth (Hendrik Poorter A C , Jonas Bühler A , Dagmar van Dusschoten A , José Climent B and Johannes A. Postma A) Functional Plant Biology 39(11) 839-850 http://dx.doi.org/10.1071/FP12049