Stimulation of photosynthetic characteristics of Ginkgo biloba L. during leaf growth

Photosynthetic pigments, biochemical activities and chlorophyll a fluorescence kinetics were investigated to survey the photosynthetic characteristics of Ginkgo biloba L. during leaf growth. The content of total chlorophyll increased rapidly while the content of carotenoids changed a little. The content of ATP, the activity of O2 evolution of chloroplasts, the electron transport activities, the activity of photophosphorylation and the activities of Ca2+ - and Mg2+ - ATPase were strengthened. All leaves at various growing stages exhibited typical chlorophyll ? fluorescence transient, the intensity of fluorescence in the chlorophyll ? fluorescence transient (OJIP) increased during leaf growth. Photosynthetic abilities gradually increased as the leaves grew. DOI: http://dx.doi.org/10.3329/bjb.v43i1.19749 Bangladesh J. Bot. 43(1): 73-77, 2014 (June)

Sensitivity of Antarctic freshwater algae to salt stress assessed by fast chlorophyll fluorescence transient

In this study, we investigated the effects of salt stress (2 mM NaCl) on excitation energy transfer from light harvesting complexes to photosystem II (PS II) in two Antarctic algal species: Klebsormidium sp. and Zygnema sp. Short-term salt stress led to a significant changes in the shape of chlorophyll fluorescence transient (OJIP). Analyses of the polyphasic fluorescence transients (OJIP) showed that the fluorescence yield at the phases J, I and P declined considerably with the time of exposition to salt stress. In both experimental species, OJIP transients reached lowest values of chlorophyll fluorescence signal after 30/60 min. of NaCl exposition. Then, OJIP shape and chlorophyll fluo-rescence showed species-specific recovery and rised towards original values (about 2/3 of untreated control). Analyses of chlorophyll fluorescence parameters derived from OJIPs showed that salt stress led to a decrease in the maximal efficiency of PS II photo-chemistry (FV/FM) in Zygnema sp. but not Klebsormidium sp. The results indicated that the probability of excitation energy transfer before and beyond QA, and the yield of electron transport beyond QA is limited by salt-induced stress in Zygnema sp. In addition, salt stress resulted in a decrease in the photosynthetic electron transport per PS II reaction center, but both increase and decrease in the trapping per PS II reaction center was found. Performace index (PIabs) was affected negatively in Zygnema sp. but possitively Klebsormidium sp. indicating that the latter species was more resistant to salt stress than Zygnema sp.

Changes of Photosynthetic Behaviors inKappaphycus alvareziiInfected by Epiphyte

Epiphytic filamentous algae (EFA) were noted as a serious problem to reduce the production and quality ofK. alvarezii. The morphological studies revealed that the main epiphyte onK. alvareziiwasNeosiphonia savatieriin China. Though the harmful effects of EFA on the production ofK. alvareziihave been reported, the detailed mechanism of theN. savatieriin limiting the production ofK. alvareziihas not been studied yet. The present paper studied the effects ofN. savatieriinfection on photosynthetic behaviors inK. alvareziiby detecting chlorophyll fluorescence transient in vivo. The results revealed that damage of oxygen-evolving complex (OEC), decrease of active reaction centers (RCs), and the plastoquinone (PQ) pool as well as significant reduction in the performance indexes (PI) of PSII were caused by the infection ofN. savatieri. The influence ofN. savatierion photosynthetic activity ofK. alvareziishould be one of the important reasons to reduce the production ofK. alvareziiinfected byN. savatieri.