Tomato root senses horizontal/vertical mechanical impedance and correspondingly modulates root/shoot metabolome

Plant root encounters coarse environs right after emergence from the seed. Little is known about metabolic changes enabling to overcome soil impedance. It also not whether roots respond differently hardness when grown in horizontal and vertical orientation. We grew tomato (Solanum lycopersicum) seedlings vertically or horizontally on agarose with increasing (0.2 % → 1.2 %). examined morphology of shoots seedling profiled phytohormones, primary metabolite levels, transcript levels related genes respective organs. Tomato horizontally, hardness, exhibited lateral proliferation, shorter hypocotyl, root. In tip, increase elicited loss amyloplast staining; induced reactive oxygen species, nitric oxide accumulation. The level indole butyric acid, zeatin, jasmonates, salicylic acid markedly differed shoot exposed hardness. Increasing lowered acetic elevated abscisic level, while increased ethylene emission was confined horizontally-impeded seedling. trajectories metabolomic shift distinctly between vertically/horizontally-impeded root/shoot. root, amino acids were major affected group, sugars group. Commonly metabolites shoot, trehalose, dopamine, caffeoylquinic suberic hallmarked signature for Snf1-related protein kinase1a (SnRK1a) expression root/shoot implying regulation homeostasis by SnRK1 signalling module. lower E2Fa may lead growth inhibition reduced meristematic activity. Our study highlights importance facilitating ramification soil. Though a common denominator, distinguishes horizontal/vertical orientation correspondingly modulates level. Altogether, data uncovers ABA, E2Fa, as key regulators hardness-induced seedlings.