The effects of natural, overwintering conditions on photosystem I and photosystem II activity were examined in isolated thylakoids of periwinkle (Vinca minor L.), an endemic, cold-tolerant, herbaceous evergreen. DCMU-Insensitive photosystem I activity (ascorbate/dichlorophenolindophenol --> methylviologen) exhibited a twofold increase in light-saturated rates upon exposure to low temperature an...

1. The percent inhibition of oxygen evolution by a given herbicide concentration is the same at various light intensities except at very low intensities where the percent inhibition becomes larger. The same results are obtained with the herbicide DCMU. 2. The concentration of DCMU causing 50% inhibition of oxygen evolution decreases with de­ creasing chloroplast (and thus of chlorophyll) concen...

The effects of irrigation water salinity on growth, chlorophyll contents, proline and nutrients accumulation and K/Na ratio in three walnut cultivars was investigated. Three irrigation water salinity levels with electrical conductivities of 1,5, 3, and 5.0 dS/m and tap water as a control treatment were used in a randomized design with four replications. Irrigation practices were realized by con...

Photosynthetic effects of the leaves extracts from Ipomoea cairica on Parthenium hysterophorus L were studied. Ipomoea cairica dried leaf powder (20g) was dissolved in distilled water (200ml) for foliar application. The seedlings were maintained under natural condition in Insect free net house. The experiment was carried out to analyze the effects of Ipomoea cairica leaves extract by measuring ...

The fluorescence lifetime of chlorophyll a gives information about the primary photo-physical events in photosynthesis. Most of the light energy absorbed by chlorophylls is utilized for photochemistry. There are two main additional pathways competing for the absorbed light energy: fluorescence and radiationless internal conversion (heat). Only a few percent of the absorbed energy proceeds along...

and an increased chlorophyll b to chlorophyll a ratio for better light capture in low light. Furthermore, an Ostreobium strain living in a coral skeleton, where nearly all of the red light has been captured by the zooxanthellae in the coral tissue, has been shown to have modified chlorophyll with a spectrum shifted towards far-red wavelengths. As zooxanthellae cannot use far-red light, more of ...

A reverse-phase h.p.l.c. technique was used to estimate the concentration of chlorophyll b in phytoplankton cultures, fecal pellets of Calanuipacificus, and suspended paniculate matter from the Central North Pacific, Oregon coastal waters, and Dabob Bay (a temperate fjord in Puget Sound, WA, USA). The purpose was to assess the distribution of this pigment in the euphotic zone and its effect on ...

Profiles of N(2) fixation, O(2) production (gross photosynthesis), O(2) concentration, chlorophyll a concentration, and photon fluence rates were measured with 50-mum resolution in colonies of the heterocyst-forming cyanobacterium Nostoc parmelioides. Microelectrode measurements were made after 20 h of incubation under N(2) gas. Colonies were frozen, and 50-mum sections were prepared by using a...