Stimulant effect of plant activator BION on photosynthesis and its inhibitory effect on pathogenic fungi

Spraying of wheat seedlings with aqueous preparations of CGA 245704 (BION) caused a slight decrease in chlorophyll content accompanied by the stable increase in the rate of O₂ evolution per chlorophyll. Stimulant effect of BION on photosynthetic activity depended on both the ai concentration and number of treatments. Biophysical methods based on the registration of slow fluorescence induction and thermoluminescence of wheat leaves revealed the stimulation of photosystem II activity and the increase in the rate of electron transport between the photosystems in treated plants. It is also shown that BION itself can show a partial fungitoxic activity because it slowed down the germination of Erysiphe graminis f.sp. tritici fungi. This is obviously the reason for partial protective effect of BION when it was applied after the inoculation of wheat seedlings with the pathogen.

Drought resistance of hard wheat cultivars measured by a rapid chlorophyll fluorescence test

SummaryDisks of hard wheat (Triticum durum Desf.) leaves subjected to rapid desiccation over 4 h showed noticeable changes in the shape of the in vivo chlorophyll fluorescence induction curves. In drought-sensitive varieties (such as Claridoc), water stress resulted in a strong inhibition of the slow fluorescence induction transients. In particular, the fluorescence quenching rate was markedly decreased in water-stressed leaf disks. In contrast, leaves of drought-resistant varieties (such as Aouedj) showed only minor changes in chlorophyll fluorescence. The results of this investigation suggest that the slow transient of the in vivo chlorophyll fluorescence induction phenomenon may provide a simple method for selecting drought-tolerant wheats.