Evidence of auxin involvement in root growth promotion by Al3+ in Camellia sinensis, an Al3+ accumulator species

• Grant number: 24/14995-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• End date: December 31, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Brenda Mistral de Oliveira Carvalho
• Grantee: Florence Costa Gomes
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Aluminum (Al) is toxic to most plants, especially in acidic soils, where it inhibits root growth and the uptake of water and nutrients. In addition to causing mechanical damage to the root system, Al disrupts the balance of the hormones auxin (Aux) and ethylene, inhibiting cell division and elongation in the roots. On the other hand, some species tolerate Al by exuding organic acids from the roots, which prevent its absorption. Others tolerate it internally, accumulating Al without exhibiting toxicity symptoms. Interestingly, Al is considered beneficial for root growth in some accumulator species, such as Camellia sinensis (Theaceae). In this species, the absence of Al results in inhibited root growth and necrosis, possibly due to an imbalance in Aux. Therefore, it is expected that this species, when exposed to Al but also to inhibitors of Aux action or transport, will show reduced root growth compared to plants exposed to Al without the inhibitors. To test this hypothesis, plants will be subjected to 500 ¼M Al or no Al exposure, with both groups being weekly treated with the Aux transport inhibitor naphthylphthalamic acid (NPA) and the Aux action inhibitor p-chlorophenoxyisobutyric acid (PCIB). Other groups of plants will not be exposed to the inhibitors, resulting in six treatments: (1) 0 ¼M Al; (2) 500 ¼M Al; (3) 0 ¼M Al + NPA; (4) 500 ¼M Al + NPA; (5) 0 ¼M Al + PCIB; (6) 500 ¼M Al + PCIB. Root growth, plant height, number of leaves and internodes, and stem diameter will be measured at 0, 7, 15, 30, 45, 75, and 90 days, in addition to organ biomass, relative water content, and Al concentration in the organs.