Role of adventitious roots in water transportation and development of tomato (Solanum lycopersicum)

In plants, xylem conduits transport water from underground roots to leaves under negative pressure. Although adventitious roots (ARs) from the stem are formed in many plants, the relationship between the water-conducting systems of ARs and plant development remains poorly understood. Tomato (Solanum lycopersicum L.), a species of considerable economic importance worldwide, possesses well-developed ARs. Physiological studies on the movement of water and mineral nutrients in plants with ARs (AR plants) may contribute to the improvement of cultivation techniques for tomato plants. In this study, we conducted a hydroponic experiment to elucidate the physiological characteristics of water conduction and plant development in tomato AR plants. Within a week of hydroponic treatment, the formation of ARs was observed in the stem immersed in culture solution. The amount of water absorbed by the ARs was similar to that absorbed by the underground roots. In control plants without ARs, the hydraulic conductance of the stems near the ground was lower than those at a distance of approximately 40-60 cm above the ground. However, in AR plants, hydraulic conductance between the stem with the ARs and that near the ground was similar and increased above the region where ARs were formed (approximately 60 cm above the ground). Furthermore, AR plants showed higher total water absorption, plant length, and total fruit weight than control plants. Thus, ARs formed on the stem may improve the water and mineral absorption. Our results showed that ARs actively supported plant development.