Banca de DEFESA: RAQUEL YELLIN CASTAÑEDA VENEGAS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE: RAQUEL YELLIN CASTAÑEDA VENEGAS
DATA: 28/03/2025
HORA: 08:30
LOCAL: DBI 03 - Anfiteatro do Setor de Fisiologia Vegetal
TÍTULO:

NITROGEN REMOBILISATION IN SUGARCANE PLANT UNDER DROUGHT STRESS AND REHYDRATION CONDITIONS

PALAVRAS-CHAVES:

¹⁵N isotopic labelling, stable isotopes, nitrogen use efficiency, water stress, Saccharum spp.

PÁGINAS: 50
GRANDE ÁREA: Ciências Agrárias
ÁREA: Agronomia
RESUMO:

Drought stress is a major limitation on sugarcane (Saccharum spp.) productivity, restricting nitrogen uptake and assimilation. Under such conditions, internal nitrogen remobilisation becomes a vital mechanism to sustain plant growth and development. This study aimed to investigate the effects of drought stress and rehydration on nitrogen remobilisation in sugarcane (cv. CTC9001bt), with a specific focus on the interaction between nitrogen and carbon metabolism. To achieve this, we assessed nitrogen metabolism enzyme activities, and traced nitrogen redistribution using ¹⁵N isotopic labelling. Additionally, we analysed the interactions between nitrogen and carbon metabolism during drought stress and rehydration phases. Plants were cultivated under well-watered and water-deficit regimes in a controlled glasshouse environment, and physiological, biochemical, and isotopic assessments were conducted at maximum stress and after rehydration. The results demonstrated that drought stress significantly reduced plant height, leaf water potential, stomatal conductance, photosynthetic rates, and transpiration, accompanied by an increase in carbon isotope discrimination (Δ¹³C). Nitrogen remobilisation was increased under drought conditions, with preferential allocation to roots and sheath leaves, contributing to better nitrogen use efficiency (NUE). Concurrently, the accumulation of proline, soluble sugars, starch, and carotenoids supported osmotic adjustment and photoprotection. Following rehydration, nitrogen was redistributed to photosynthetically active tissues, promoting partial recovery of chlorophyll content, photosynthetic activity, and nitrogen metabolism. However, limitations in stomatal conductance and carbon assimilation persisted, indicating incomplete recovery. The activity of key nitrogen metabolism enzymes, including glutamine synthetase (GS) and nitrate reductase (NR), was modulated by water availability. Changes in the C:N ratio reflected dynamic adjustments in resource allocation during stress and recovery phases. These findings shows the importance of integrated nitrogen and carbon metabolic responses in sugarcane’s adaptation to drought and rehydration. The use of ¹⁵N isotopic labelling provided novel insights into nitrogen remobilisation dynamics, with practical implications for improving nitrogen use efficiency and resilience in sugarcane cultivated under water-limited conditions.

MEMBROS DA BANCA:
Externo à Instituição - DANIEL AMORIM VIEIRA - UFLA (Suplente)
Externo à Instituição - EDUARDO MARIANO - USP (Membro)
Externo à Instituição - JOSE LAVRES JUNIOR - USP (Membro)
Interno - MEWAEL KIROS ASSEFA (Suplente)
Presidente - PAULO EDUARDO RIBEIRO MARCHIORI (Membro)