Water deficit affects photosynthetic induction in Bauhinia forficata Link (Fabaceae) and Esenbeckia leiocarpa Engl. (Rutaceae) growing in understorey and gap conditions

Abstract

In tropical forests, light is considered the most limiting resource for plant growth and reproduction. Besides light, water deficit leads invariably to a decrease in photosynthesis. Thus, despite of the unquestionable role of light in CO2 assimilation (A), it is expected that water deficit affects and limits the light utilization by plants. In this study, we investigated how water deficit influenced the photosynthetic induction of the early successional tree Bauhinia forficata (Fabaceae) and the late successional Esenbeckia leiocarpa (Rutaceae) in the understorey and in the forest gap. Field measurements were carried out in June and August 2006 in plants of approximately two-years-old. In August, the plants were subjected to a period of 45 d without rain characterizing a water deficit situation. Leaf water potential was significantly lower in August, both in forest gap and understorey (-2.5 and -3.8 MPa, respectively), than in June (-0.6 and -1.6 MPa, respectively). In June, both species presented a rapid increase in A after a saturating light pulse under gap conditions. However, in the understorey the increase in A was slower in B. forficata than in E. leiocarpa. In August water deficit limited the increase in Amax in both species, indicating that potential utilization of increasing irradiance was reduced by water deficit conditions. The constrain in Amax was less pronounced in the understorey where plants at least reached the irradiance compensation point, whereas carbon gain by photosynthesis of the plants grown in the gap did not compensate the carbon loss by respiration.

Crescimento de combinações copa - porta-enxerto de citros sob estresse hídrico em casa de vegetação

“…ex Tanaka) foram irrigadas com apenas 40% da evaporação do Tanque Classe A. Em estudo semelhante, Castel (1994) constatou, aplicando seis níveis de irrigação entre 30 e 200% da evaporação em plantas jovens de 'Clementina de Nules' , relação linear entre o aumento no diâmetro do tronco e o aumento na taxa de aplicação de água. Em condições de baixa disponibilidade de água no solo vários processos metabólicos das plantas podem ser influenciados, como o fechamento estomático, a redução da fotossíntese e transpiração (Portes et al, 2006), fatos que tendem a diminuir o elongamento celular e, assim, o crescimento e o desenvolvimento das plantas.…”

Evidence of higher photosynthetic plasticity in the early successional Guazuma ulmifolia Lam. compared to the late successional Hymenaea courbaril L. grown in contrasting light environments

“…However, in H. courbaril the highest Chl contents (a, b and total) were detected in leaves under high light conditions. Since higher SLW is expected in high light grown leaves (Krall et al, 1995;Murchie and Horton, 1997;Portes et al, 2006), this unexpected result can be explained by the differences between leaf thickness in sun and shade leaves. Lichtenthaler et al (2007) also verified higher total Chl (a+b) contents per unit of leaf area in sun leaves and needles in the four tree species studied; however when expressed on a dry matter basis, shade leaves and needles presented higher Chl a+b content.…”

Frequência da irrigação ao final da produção em mudas de espécies lenhosas

“…O estresse hídrico induz a alterações no metabolismo vegetal dependendo do genótipo, da duração, da severidade e do estádio de desenvolvimento, ocasionando mudanças na alocação de foto-assimilados e nos mecanismos de adaptação e de resistência (PORTES et al 2006). A redução na altura das mudas e o aumento no diâmetro de coleto são atributos que tem servido como indicadores da boa qualidade em mudas de espécies lenhosas (DRANSKI 2013;VOLKWEIS et al 2014).…”