Acclimation of mesophyll and bundle sheath chloroplasts of maize to different irradiances during growth

Abstract

The regulation by light of the photosynthetic apparatus, and composition of light-harvesting complexes in mesophyll and bundle sheath chloroplasts was investigated in maize. Leaf chlorophyll content, level of plastoquinone, PSI and PSII activities and Lhc polypeptide compositions were determined in plants grown under high, moderate and low irradiances. Photochemical efficiency of PSII, photochemical fluorescence quenching and non-photochemical fluorescence quenching over a range of actinic irradiances were also determined, using chlorophyll a fluorescence analysis. Acclimation of plants to different light conditions caused marked changes in light-harvesting complexes, LHCI and LHCII, and antenna complexes were also reorganized in these types of chloroplasts. The level of LHCII increased in plants grown in low light, even in agranal bundle sheath chloroplasts where the amount of PSII was strongly reduced. Irradiance also affected LHCI complex and the number of structural polypeptides, in this complex, generally decreased in chloroplasts from plants grown under lower light. Surprisingly moderate and low irradiances during growth do not affect the light reaction and fluorescence parameters of plants but generated differences in composition of light-harvesting complexes in chloroplasts. On the other hand, the changes in photosynthetic apparatus in plants acclimated to high light, resulted in a higher efficiency of photosynthesis. Based on these observations we propose that light acclimation to high light in maize is tightly coordinated adjustment of light reaction components/activity in both mesophyll and bundle sheath chloroplasts. Acclimation is concerned with balancing light utilization and level of the content of LHC complexes differently in both types of chloroplasts.

Structural Organization of Photosynthetic Apparatus in Agranal Chloroplasts of Maize

“…In addition, the structure of the BS chloroplasts was suggested not to be influenced by the light intensity and was similar in plants grown in full tropical sunlight or under low irradiance (46). In contrast, our recent results have shown that various light growth conditions may alter polypeptide composition of the BS thylakoids of maize (14).…”

“…PSII activity was assayed spectroscopically by measuring the photoreduction rate of the artificial electron acceptor 2,6-dichlorophenolindophenol, as described in Ref. 14 Blue Native-PAGE and Immunodetection-Protein solubilization and BN-PAGE were performed according to Schägger et al (29) and Kügler et al (30) with slight modifications. Thylakoid membranes (50 g of Chl) were sedimented at 7,000 ϫ g for 5 min at 4°C and resuspended in a buffer composed of 5 mM EACA, 50 mM imidazole-HCl, pH 7, 50 mM NaCl, 0.5 mM EDTA.…”

“…Alternatively, a weak energetic coupling between LHCII and PSII may decrease the F v /F m ratio by increasing the F o emission component. Indeed, the relatively large pool of LHCII present in BS chloroplasts (14) may not be completely connected to the reduced number of PSII reaction centers. Finally, the occurrence of sustained energy spillover from PSII to PSI may also decrease the fluorescence yield of PSII and thus the F v /F m ratio.…”

“…It appears that such contradicting reports are due to the differences in the BS isolation procedures and, as a consequence, a degree of intactness of PSII. In addition, it was demonstrated that the level of PSII activity in BS chloroplasts, as well as the presence of the oxygen-evolving complex subunits, depends on the differences in the age of the source leaf tissue, contamination with MS chloroplasts during isolation procedures, and illumination conditions (14,20,21). The apparent existence of the D1 degradation/repair cycle in BS chloroplasts and the identification of proteolytic enzymes responsible for these processes in these organelles confirm that PSII indeed plays an important function in the BS agranal membranes (22).…”

Profiling of Indoor Plant to Deteriorate Carbon Dioxide Using Low Light Intensity

“…Other than that, all plant ages that involved in this study is one year. Before experimental were conducted, all plants involved must be assimilated with the indoor environment for at least two months, as recommended by Drozak and Torpy [29,26]. In assimilation process, allowing plants to tolerate with indoor environment, where lighting and temperature is different compared to their original habitation.…”