High relative humidity triggers adventitious root primordia elongation in tomato plants

VIDOZ, M.L.; MIGNOLLI, F.

Congreso; XXXIII Argentinian Meeting of Plant Physiology; 2021

Tomato (Solanum lycopersicum L.) plants are a model horticultural species not only to study fleshy fruit formation but also to unravel plant responses to the environment, such as the formation of adventitious roots (ARs) from submerged stems. We have previously observed that an increase in relative humidity (RH) is enough to induce the elongation of preformed AR primordia. Considering the energetic cost of producing fast-growing roots and the consequent intricate and strict regulation of ARs, it is surprising that a mere increase in water vapor can trigger such a conspicuous response. Therefore, the purpose of this study was to increase our understanding of the mechanism behind high RH-induced ARformation in tomato plants. We have first exposed the base of four weeks old plants to a range of water vapor content in order to determine whether there is a threshold below which AR development does not take place. Following, we assessed the role of auxin, ethylene, gibberellins and abscisic acid on the induction of AR primordia elongation by applying specific inhibitors and exogenous hormones to the hypocotyls, before exposing them to high RH. We have observed that there is no AR induction below 78% RH, and that the number and length of ARs increased proportionally with the RH level. Moreover, the process seems to be regulated by auxin and gibberellins, as the inhibition of both hormones resulted in a reduction in the number and length of ARs.