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Growth, yield and reproduction of dwarf tomato grown under simulated microgravity conditions

Abstract A closed hydroponic system combined with a horizontal uniaxial clinostat has been used to grow tomato plants (Solanum lycopersicum L.) under simulated microgravity conditions. The study was carried out to evaluate the quanti-qualitative traits (growth, yield and quality) of the dwarf tomato variety ‘Micro-Tom’ grown under simulated microgravity conditions and to determine if tomato plants would complete their life cycle (‘seed-to-seed’). Morphological and growth characteristics of ‘Micro-Tom’ were modified during clinorotation treatment. The ‘Micro-Tom’ plants grown under simulated microgravity exhibited a spreading growth and an increasing of the internode length. Total fruit yield, small fruit yield, leaf area, leaf dry weight, fruit dry weight, total dry weight and shoot – root ratio were lower in the clinorotated tomato plants than those grown in the control treatment. Foliar amount of carotenoids, and chlorophyll a and b were also substantially reduced under simulated microgravity conditions. Quality parameters (total soluble solids and fruit dry matter) of tomato plants were also negatively affected by clinorotation. The number of flowers per plant was increased by 32% in clinorotated plants versus controls. Fruit setting was reduced by 46% under clinorotation, while no significant difference was recorded for the pollen fertility and the seed number in small and large fruits. Clinorotation-exposed and control seeds were used in a germination trial in order to evaluate whether the seeds so formed were viable and if subsequent generations might be obtained in microgravity. Seeds formed under simulated microgravity proved to be biologically and functionally complete (germination = 78.6%) showing that ‘Micro-Tom’ plants could realize complete ontogenesis, from seed to seed in microgravity.