Photosynthetic acclimation of the liana Stigmaphyllon lindenianum to light changes in a tropical dry forest canopy

Abstract

Tropical plant canopies show abrupt changes in light conditions across small differences in spatial and temporal scales. Given the canopy light heterogeneity, plants in this stratum should express a high degree of plasticity, both in space (allocation to plant modules as a function of opportunity for resource access) and time (photosynthetic adjustment to temporal changes in the local environment). Using a construction crane for canopy access, we studied light acclimation of the liana Stigmaphyllon lindenianum to sun and shade environments in a tropical dry forest in Panama during the wet season. Measured branches were randomly distributed in one of four light sequences: high- to low-light branches started the experiment under sun and were transferred to shade during the second part of the experiment; low- to high-light branches (LH) were exposed to the opposite sequence of light treatments; and high-light and low-light controls , which were exposed only to sun and shade environments, respectively, throughout the experiment. Shade branches were set inside enclosures wrapped in 63% greenhouse shade cloth. After 2 months, we transferred experimental branches to opposite light conditions by relocating the enclosures. Leaf mortality was considerably higher under shade, both before and after the transfer. LH branches reversed the pattern of mortality by increasing new leaf production after the transfer. Rates of photosynthesis at light saturation, light compensation points, and dark respiration rates of transferred branches matched those of controls for the new light treatment, indicating rapid photochemical acclimation. The post-expansion acclimation of sun and shade foliage occurred with little modification of leaf structure. High photosynthetic plasticity was reflected in an almost immediate ability to respond to significant changes in light. This response did not depend on the initial light environment, but was determined by exposure to new light conditions. Stigmaphyllon responded rapidly to light changes through the functional adjustment of already expanded foliage and an increase in leaf production in places with high opportunity for carbon gain.

Physiological aspects of sun and shade leaves of Lithraea molleoides (Vell.) Engl. (Anacardiaceae)

“…Besides the light effect on the photosynthetic process itself, synthesis and degradation of chlorophylls were also directly associated to light intensity (Engel and Poggiani, 1991). Avalos and Mulkey (1999) Significant leaf structural changes were also identified in L. molleoides (Dias, 2005), but no photosynthetic rate increase was observed in leaves receiving more light. The higher level of chlorophyll in the shade leaves combined with structural change, such as greater intercellular space area of the spongy parenchyma, could be related with the non-differentiation of the photosynthetic rate between sun and shade leaves of L. molleoides (Dias, 2005).…”

“…Leaf response to different light conditions vary widely among species (Rijkers et al, 2000). Overall, leaves growing under intense light display the following characteristics: higher mesophyll width, cuticule and photosynthetic rate (Campostrini et al, 2001;Avalos and Mulkey, 1999;Oguchi et al, 2003). The highest photosynthetic rate in leaves exposed to intense light is associated to important morphoanatomic adaptations, especially greater cuticle and palisade parenchyma thickness, which allow the plant to minimize water loss and transmit the excess of light more directly, under more xeric conditions of the upper portion of the tree crown (Selleck andShupert, 1957 apud Martinez andMedri, 1985) and to prevent photoinhibition (Lemos-Filho, 2000).…”

Leaf optical properties of two liana species Canavalia parviflora Benth. and Gouania virgata Reissk in different light conditions

“…However, some authors focused their attention on species that belong to other life forms, as lianas (Putz & Mooney 1991, Avalos & Mulkey 1999, Kazda & Salzer 2001, Sanches & Válio 2002. The increasing scientific interest in lianas is related to their role in forest regeneration and to their contribution to the maintenance of biodiversity and whole-forest transpiration (Restom & Nepstad 2001, Schnitzer & Bongers 2002.…”

“…This is partly due to the difficulty in assessing the canopy, in identifying genets (sexually produced plants) or ramets (vegetatively produced plants), and also to taxonomic uncertainties, (Avalos & Mulkey 1999, Schnitzer & Bongers 2002.…”

Photosynthetic acclimation within individual Typha latifolia leaf segments

“…The local light environment influences the morphological development of leaves in many species, resulting in comparatively thick leaves in bright locations Hikosaka, 1996;Niinemets, 2007). Fully expanded leaves have a limited capacity for morphological change (Sims and Pearcy, 1992;Evans and Porter, 2001;, and acclimation by these leaves requires biochemical changes in carboxylation, electron transport, and light harvesting, as well as modifications to chloroplast structure and orientation (Sebaa et al, 1987;De la Torre and Burkey, 1990a, b;Avalos and Mulkey, 1999;Frank et al, 2001;Murchie et al, 2002;Oguchi et al, 2003Oguchi et al, , 2005Walters, 2005).…”