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Responses of parameters related with photosynthesis and the involvement of various factors in photosynthetic damage in two chickpea genotypes, Gokce (tolerant) and Kusmen (sensitive) under drought stress were assessed. Photosynthetic pigment content decreased under drought stress in two genotypes. Significant decreases in gs, Pn and E were determined in Kusmen. No significant change in these parameters was measured in Gokce under drought stress. Fv/Fm, ΦPS2 and ETR decreased in drought stressed plants of Kusmen as compared to control plants however Fv/Fm, ΦPS2 and ETR did not change in Gokce under drought stress. Increases in NPQ were determined under stress in both genotypes. Drought stress did not affect rubisco activity and rubisco concentration in Gokce while, the activity and the content declined in Kusmen. The drought tolerance of the Gokce genotype is a consequence of a balance among leaf water potential, stomatal conductance, photosynthesis, and transpiration. On the other hand, photosynthesis in Kusmen may be not only restricted by stomatal limitations but also by non-stomatal limitations under drought stress.

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We studied the changes in antioxidant system and chlorophyll fluorescence parameters in post-stress emerging Ctenanthe setosa (Rosc.) Eichler (Marantaceae) plants (PSE plants) having reduced leaf area under drought stress causing leaf rolling and re-watering. PSE plants were compared to primary stressed plants (PS) in previous studies. The parameters were measured at different visual leaf rolling scores from 1 to 4 (1 is unrolled, 4 is tightly rolled and the others is intermediate form). Water potentials and stomatal conductance of leaves were gradually decreased during leaf rolling. Similarly, maximum quantum efficiency of open PS II center and quantum yield of PS II decreased during the rolling period. Non-photochemical quenching of chlorophyll fluorescence decreased at score 2 then increased while photochemical quenching did not change during leaf rolling. Electron transport rate decreased only at score 4 but approximately reached to score 1 level after re-watering. Superoxide dismutase activity was not constant at all leaf rolling scores. Ascorbate peroxidase, catalase and glutathione reductase activities generally tended to increase during leaf rolling. Lipid peroxidation and H 2 O 2 content increased at score 2 but decreased at the later scores. On the other hand, O 2 ·− production increased during the rolling period. After re-watering of the plants having score 4 of leaf rolling, antioxidant enzyme activities were lower than those of score 1. Other physiological parameters also tended to reach the value of score 1. The results indicated that PSE plants gained drought tolerance by reducing leaf area effectively induced their antioxidant systems and protected the photosynthesis under drought stress similar to PS plants.

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Acta Botanica Hungarica
Authors:
C. Çi̇rak
,
M. Odabaş
,
A. Ayan
,
B. Sağlam
, and
K. Kevseroğlu

The genus Hypericum has attracted scientific interest for recent years, since it is a source of a variety of compounds including hypericin. The present study was conducted out to develop leaf area prediction models for some Hypericum species containing hypericin, namely H. pruinatum, H. perfoliatum, H. aviculariifolium subsp. depilatum var. depilatum (endemic), H. montanum, H. montbretii, H. linarioides, H. triquetrifolium, H. bithynicum and H. perforatum growing wild in Northern Turkey. Lamina width, length and leaf area were measured without destroying to develop the models. The actual leaf areas of the plants were measured by Placom digital planimeter, and multiple regression analysis with Excel 7.0 computer package program was performed for the plants separately. The produced leaf area prediction models in the present study were formulised as LA = (a) + (b 1 × L) + [b 2 × (L × W)] + (b 3 × L 2 ) + (b 4 × W 2 ) + [b 5 × (L × W 2 ] + [b 6 × (L 2 × W)] + [b 7 × (L 2 + W 2 )] where LA is leaf area, Wis leaf width, L is leaf length and a, b 1 , b 2 , b 3 , b 4 , b 5 , b 6 , and b 7 are coefficients. R 2 values varied with species from 0.80 in H. aviculariifolium subsp. depilatum var. depilatum to 0.97 in H. pruinatum . All R 2 values and standard errors were found to be significant at the p < 0.001 level.

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