Acclimation of leaves to low light produces large grana: the origin of the predominant attractive force at work

Abstract

Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by nonstacked thylakoids, thereby being able to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to the environment. Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids. The net surface charge of thylakoid membranes is negative, even in low-light-grown plants; so an attractive force is required to overcome the electrostatic repulsion. The theoretical van der Waals attraction is, however, at least 20-fold too small to play the role. We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids in the dark on addition of Mg 2þ , to be zero or marginally positive (endothermic). The Gibbs free-energy change for the spontaneous process is necessarily negative, a requirement that can be met only by an increase in entropy for an endothermic process. We conclude that the dominant attractive force in thylakoid stacking is entropy-driven. Several mechanisms for increasing entropy upon stacking of thylakoid membranes in the dark, particularly in low-light plants, are discussed. In the light, which drives the chloroplast far away from equilibrium, granal stacking accelerates non-cyclic photophosphorylation, possibly enhancing the rate at which entropy is produced.

Mutation of the ALBOSTRIANS Ohnologous Gene HvCMF3 Impairs Chloroplast Development and Thylakoid Architecture in Barley due to Reduced Plastid Translation

“…high light or blue light (Mostowska, 1986). An interruption of the electron transport between photosystem II and photosystem I triggers also the formation of large thylakoid stacks (Meier and K. Lichtenthaler, 1981; Jia et al, 2012). Large grana have been further described in mutants with impaired starch formation (Hausler et al, 2009).…”

High Light Intensity Increases the CAM Expression in “MD-2” Micro-Propagated Pineapple Plants at the End of the Acclimatization Stage

“…During Phase III of CAM plants the stomata are closed, which can lead to a parallel increase in both the intercellular partial pressure of O 2 (piO 2 ) and CO 2 (pi-CO 2 ). An increased O 2 level in Phase III behind closed stomata can promote overproduction of H 2 O 2 /ROS in CAM plants [30]. SOD activity in pineapple plants studied in this work showed a treatment-dependent response.…”

“…The higher chlorophyll content in plants leaves under HL conditions during thirty days is an indicative of better acclimation to sun conditions. Higher values of total chlorophyll without a concomitant decrease in chlorophyll a/b ratio during acclimation of photosynthetic tissue to lower light levels, will occur if there is an increase in the number, but not size, of the "photosynthetic units" (PSU) in the tissue, as increases in PSU size in response to lower light levels typically reflect, in particular, an increase in the light-harvesting portions of the photosynthetic pigment/protein complex in both photo systems [30]. Also it can explain that pineapple plants under HL and LL conditions showed similar chlorophylls a/b ratio.…”

Light‐harvesting superstructures of green plant chloroplasts lacking photosystems

“…Giant grana have been previously observed in rare plants grown under very shaded environment (Jia et al . ). Indeed, abaxial cell layers of Trapa natans leaves floating on the water surface displayed giant grana (Bassi ; Nedukha ).…”

“…The supergrana revealed frequent membrane bifurcations that are likely to be the major structural factor that stabilizes stacking. Giant grana have been previously observed in rare plants grown under very shaded environment (Jia et al 2012). Indeed, abaxial cell layers of Trapa natans leaves floating on the water surface displayed giant grana (Bassi 1986;Nedukha 2012).…”