SUMMARYAs photosynthesis is the basic process during which light energy is absorbed and converted into organic matter, the importance of the plant pigment chlorophyll (a and b forms) as an intermediary in transformation of the absorbed solar energy and its activity in the process of photosynthesis and synthesis of organic substances in plants are crucial. Therefore, this paper provides an overview of methods for monitoring the optical activity of chlorophyll molecules and methods (non-destructive and destructive) for quantification of chlorophyll in plants. These methods are used to estimate the effects of different stress factors (abiotic, biotic and xenobiotic) on the efficiency of photosynthesis and bioproductivity, aiming to assess the impact that these limiting factors have on the yield of various cultivars. Also, those methods for analysis of chlorophyll optical activity and/or content are appropriate for assessing the reaction of weed species to different agricultural practices (mineral nutrition, treatment by herbicides, etc.) and studies of different aspects of weed ecophysiology and their influence on crop harvest. Keywords: Chlorophylls; Photosynthesis; Plant health Abbreviations: LHCP 2 , LHCP 1 : antenna complexes in photosystems II and I with the main function of absorbing (sun)light quantum and converting it into excitation energy of chlorophyll molecules (excitons); PS II and PS I: photosystems II and I; RC: reaction centers of PS II and PS I with the function of transforming the energy of exciton into primary photochemical reaction

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The correlation analysis and the path coefficient analysis were applied to wheat data set with the objective to determine the effect of five physiological traits (early vigor, early maturity, leaf senescence, flag leaf area and total biomass per plant) on grain yield under irrigation and drought stress conditions. The data set consisted of 100 divergent genotypes tested in four-year field trials. Highly significant correlations were found between grain yield, early vigor and total biomass per plant in both treatments. A highly negative correlation was detected between grain yield and days to flowering, as well as, between grain yield and leaf senescence in both treatments. The path analysis revealed a highly significant direct effect of days to anthesis and total biomass per plant on grain yield. Early vigor, leaf senescence and the flag leaf area had a significant indirect effect on grain yield via days to anthesis and total biomass per plant. Early vigor, early maturity and leaf senescence were found to be suitable for wheat breeding under different moisture regimes. These traits can be evaluated quickly and easily, and thus they can be used for the evaluation of large populations

The effect of arsenic (32 -96 μM) on the phosphorus content and Chl fluorescence was studied in soybean (Glycine max Merril) grown in the nutrient solution with and without phosphorus. The increased concentration of As led to the decrease in P content in plant organs. Parameters of Chl fluorescence of soybean leaves in the presence of these As concentrations did not show significant changes.Additional key words: Glycine max, photosystem 2, quantum yield. ⎯⎯⎯⎯Pollution of the soil and atmosphere by arsenic (As) is conditioned by the industry development. Copper smelters and thermal plants are great pollutants of the atmosphere. According to Smirnov and Muravin (1977) natural As content in the soil is 5 mg(As) kg -1 (soil). As, an analogue to phosphorus, is absorbed from the soil by P transporters. As inhibits P uptake in barley (Asher and Reay 1979) and Arabidopsis (Dunlop et al. 1997). In many of plant species, arsenates and arsenites have an affinity for thiols, such as glutathione. Furthermore, phytochelatins are formed as a response to As (Schmöger et al. 2000). Hartley-Whitaker et al. (2000a, 2000b confirmed that As-tolerant Holcus lanatus L. had higher phytochelatins concentrations than As-intolerant species. Hence, similar to heavy metals, As also mobilises the socalled nonenzymic antioxidants, such as glutathione, ascorbates, and phytochelatins. In order to investigate As effects on the uptake and distribution of phosphorus (P) in plant organs and chlorophyll (Chl) fluorescence in the soybean leaves, different As concentrations were used: 2.4, 4.8, 6.0, and 7.2 g(As) m -3 , corresponding to 32, 64, 80 and 96 μM As.After the 5-d germination in the dark, plants of soybean (Glycine max Merril. cv. ZP S015) were transferred into pots with the nutrient medium of pH 7.0 (Hoagland and Arnon 1950). Plants were grown in growth chambers at a 12-h photoperiod, irradiance of 300 μmol m -2 s -1 (Sylvania cool white lamp P9GT12-CEW-VHO, Danvers, USA) and day/night temperature of 24/20 °C. Plants grown on the complete medium were the control ones. The P content in the other three variants was half or double of that in the control or zero. Plants grown with and without P were exposed to 32, 64, 80 and 96 μM Na 2 HAsO 4 for 5 d.

High-performance thin-layer chromatography (HPTLC) combined with image analysis and pattern recognition methods were used for fingerprinting of phenolic compounds present in seedlings of two maize genotypes ZP 434 (new generation hybrid, drought tolerant) and ZP 704 (older generation hybrid, drought sensitive) treated with different concentrations of 24-epibrassinolide. This is the first report of TLC chromatographic profile of phenolics’ mixtures in maize seed extracts influenced by brassinosteroid phytohormones. Nine samples of shoot of seedlings for the whole concentration range of phytohormones (5.2 × 10−7–5.2 × 10−15 M), one sample of root of seedlings treated with 5.2 × 10−15M 24-epibrassinolide, and the control samples of nontreated seedlings, for both genotypes, were analyzed. Phenolic profiles of root extracts indicate the absence of more polar compounds such as phenolic acids and glycosides present in shoot of seedlings. Also, hormones applied in higher concentrations have an inhibiting effect on the content of phenolics in ZP 434. Application of chemometric methods enables characterization of particular genotype of maize according to its phenolic profile.