Banca de QUALIFICAÇÃO: TIAGO DE SOUSA LEITE

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : TIAGO DE SOUSA LEITE
DATA : 31/01/2022
HORA: 14:00
LOCAL: Sala virtual
TÍTULO:

Título do primeiro trabalho: The interplay between leaf water potential and osmotic adjustment on photosynthetic and growth parameters of tropical dry forest trees

 

Título do segundo trabalho: Ecophysiological and biochemical responses of two tree species from a tropical dry forest to drought stress and recovery

PALAVRAS-CHAVES:

Palavras-chave do primeiro trabalho: Drought stress; Rehydration; Gas exchange; Plant biomass

 

Palavras-chave do segundo trabalho: Photosynthetic activity; Water potential; Photoprotection; Deciduous trees; Caatinga

PÁGINAS: 39
RESUMO:

Resumo do primeiro trabalho: Mimosa tenuiflora and Piptadenia stipulacea are putatively drought-tolerant trees, but little is known about their responses to drought followed by rehydration. Therefore, we studied the interplay between leaf water potential and osmotic adjustment on photosynthetic and growth parameters of these plants. A greenhouse study was conducted in a split-plot design, with two water conditions in the main plots (1 – control and 2 – drought followed by rehydration) and eight sampling dates in the subplots (1, 4 and 7 days of drought, and 1, 3, 6, 12 and 17 days of rehydration). We assessed plant water status and biochemical changes as well as leaf gas exchange and subsequent growth. Under drought stress, both tree species 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. Though these plants minimized water loss by closing their stomata, neither showed stomatal limitations to photosynthesis. The inhibition of this process during drought was probably related to mesophyll limitations as well as to a reversible downregulation of photosystems, along with adjustments of their stoichiometry. Also, water deficit triggered morphological adaptations at the whole-plant level, leading to reduced subsequent growth, mainly of the shoot in M. tenuiflora and of the roots in P. stipulacea.

 

Resumo do segundo trabalho: Droughts are predicted to increase in frequency and severity, thus affecting the functioning of forest ecosystems. However, it is not clear how the recovery dynamics of Erythrina velutina and Poincianella pyramidalis work following these events. Thus, we investigated the ecophysiological and biochemical responses of these tree species to drought stress and recovery. The study was conducted under greenhouse conditions, where the effects of two water regimes (1 – control and 2 – drought stress followed by recovery) were evaluated over time. Gas exchange parameters, leaf water potentials and biochemical attributes were measured. Under drought, 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 rewatered, 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, which can contribute to the resilience of these trees in the face of recurring droughts.

MEMBROS DA BANCA:
Externo à Instituição - EMMANUEL MOREIRA PEREIRA - INSA
Presidente - 1505717 - NILDO DA SILVA DIAS
Externo à Instituição - ROMULO MAGNO OLIVEIRA DE FREITAS - IFRN