Banca de DEFESA: TIAGO DE SOUSA LEITE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : TIAGO DE SOUSA LEITE
DATA : 10/03/2022
HORA: 19:30
LOCAL: Virtual (Google Meet)
TÍTULO:

Ecophysiology of Caatinga tree species as a function of drought stress and rehydration

PALAVRAS-CHAVES:

Tropical dry forest. Deciduous trees. Photosynthetic activity. Water potential. Osmotic adjustment.

PÁGINAS: 58
RESUMO:

Erythrina velutina, Mimosa tenuiflora, Piptadenia stipulacea and Poincianella pyramidalis are pioneer trees native to the Caatinga biome, a tropical dry forest whose composition is threatened by increasingly frequent and lasting droughts. Nevertheless, there is limited information on the recovery of these species when water availability is normalized. Therefore, their ecophysiology was studied as a function of drought stress and rehydration. Four concurrent but independent experiments were conducted under greenhouse conditions, in a split-plot design with two water regimes in the main plots (1 – control; 2 – drought followed by rehydration) and sampling times in the subplots (at varying periods of drought and rehydration). Plant water status, gas exchange parameters, biochemical attributes and subsequent growth were measured. E. velutina rapidly downregulated photosynthesis, reducing leaf gas exchange and improving water use efficiency to compensate for the temporary loss of xylem water transport, and recovered slowly after having a high consumption of non-structural carbohydrates. In contrast, the photosynthetic activity of P. pyramidalis was gradually reduced with increasing drought, but quickly recovered when rehydrated, and the leaf water potential was effectively reduced through the accumulation of proline. Although showing different mechanisms behind their drought tolerance, in both species, the full recovery of photosynthesis upon rewatering was possibly related to enhanced photoprotection by carotenoids. M. tenuiflora and P. stipulacea maintained a low leaf water potential throughout the day by accumulating compatible solutes, thus allowing a rapid and full recovery of water status when rehydrated. Even though these plants minimized water loss by closing their stomata, neither showed stomatal limitations to photosynthesis. The inhibition of this process during drought was possibly related to mesophyll limitations as well as to a reversible downregulation of photosystems, along with adjustments of their stoichiometry. Drought stress also triggered morphological adaptations at the whole plant level, leading to reduced growth, mainly of the shoots in M. tenuiflora and the roots in P. stipulacea.

MEMBROS DA BANCA:
Presidente - 1505717 - NILDO DA SILVA DIAS
Interno - 1670421 - AURELIO PAES BARROS JUNIOR
Externa ao Programa - 1289574 - NARJARA WALESSA NOGUEIRA DE FREITAS
Externo à Instituição - WANDERSON DE SOUSA MENDES - PESQUISADOR
Externo à Instituição - EMMANUEL MOREIRA PEREIRA - INSA
Externo à Instituição - ROMULO MAGNO OLIVEIRA DE FREITAS - IFRN