Banca de DEFESA: LUCAS JOSÉ REIS BARTSCH

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LUCAS JOSÉ REIS BARTSCH
Date: 11/09/2026
TIME: 14:00
LOCAL: ONLINE
TITLE:

The carbon investment in root nodules accompanies the growth reduction caused by water limitation in a fast-growing Neotropical plant

PAGES: 63
BIG AREA: Ciências Biológicas
AREA: Botânica
SUBÁREA: Fisiologia Vegetal
SPECIALTY: Ecofisiologia Vegetal
SUMMARY:

Plants frequently establish mutualistic interactions to acquire resources or services that they cannot obtain on their own. However, maintaining these interactions depends directly on carbon availability, as carbohydrates produced through photosynthesis are used both for plant growth and maintenance and to support mutualistic partners. Thus, when carbon is limited, trade-offs may arise in the allocation of resources between growth and investment in mutualisms. One of the best-described mutualistic interactions is that between plants and nitrogen-fixing bacteria, in which plants provide carbohydrates in exchange for soluble nitrogen. Despite these benefits, maintaining this interaction involves substantial energetic costs, which may constrain growth when they become disproportionate. In this context, environmental factors that restrict plant carbon balance, such as water limitation, may alter the balance between the benefits and costs of this interaction. However, it remains unclear how such constraints translate into adjustments in carbon allocation between growth and nodulation. In this study, we investigated how water limitation influences carbon allocation to growth and to interactions with nitrogen-fixing bacteria. We tested two hypotheses: (1) water restriction reduces photosynthesis and growth, altering the balance and allocation of carbohydrates among plant organs; and (2) water restriction increases the relative cost of the plant–bacterium interaction, leading to reduced investment in root nodules. To test these hypotheses, we used the annual legume Chamaecrista nictitans, cultivating 60 plants under two water conditions, 30 well-watered and 30 water-restricted, for one month. We quantified carbon assimilation and the allocation of biomass and non-structural carbohydrates to growth and nodulation. Water limitation reduced carbon assimilation and overall plant growth, with proportional reductions in biomass across different organs, accompanied by higher soluble sugar concentrations and lower foliar starch concentrations. Similarly, investment in nodulation also decreased proportionally with plant size, while sugar concentrations in nodules increased. Our results show that plants adjust their investment in nodulation in response to water limitation in proportion to the reduction in growth, maintaining relatively stable biomass allocation among organs and to nodules. This coordinated response suggests that plants may avoid an increase in the relative cost of nodulation under water stress by adjusting investment to their lower growth demand and, consequently, their demand for nitrogen.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 2887832 - ANSELMO NOGUEIRA
Membro Titular - Examinador(a) Externo à Instituição - TOMAS FERREIRA DOMINGUES - USP
Membro Titular - Examinador(a) Externo à Instituição - FLÁVIA DELGADO SANTANA - INPA
Membro Suplente - Examinador(a) Interno ao Programa - 1831780 - DANILO DA CRUZ CENTENO
Membro Suplente - Examinador(a) Externo à Instituição - TALITA CÂMARA DOS SANTOS BEZERRA - UEFS