Chlorophyll and nitrogen contents were highest in leaves of middle position, similarly as photosynthetic efficiency represented by 14C fixation (maxima in leaf 5 from the top). All the leaves lost 14C after 2 weeks of 14CO2 exposure. However, the reduction in radioactivity was less in young upper leaves than in the mature lower leaves. Leaves exported 14C-photosynthates to stem both above and below the exposed leaf. Very little radioactivity was recovered from the seeds of plants in which only first or second leaves were exposed to 14CO2 implying thereby that the carbon contribution of first two leaves to seed filling was negligible. The contribution of leaves to seed filling increased with the leaf position up to the sixth leaf from the top and after the seventh leaf their contribution to seed filling declined gradually. and Desiraju Subrahmanyam, V. S. Rathore.
Leaf area estimation is an important biometrical observation recorded for evaluating plant growth in field and pot experiments. In this study, conducted in 2009, a leaf area estimation model was developed for aromatic crop clary sage (Salvia sclarea L.), using linear measurements of leaf length (L) and maximum width (W). Leaves from four genotypes of clary sage, collected at different stages, were used to develop the model. The actual leaf area (LA) and leaf dimensions were measured with a Laser Area meter. Different combinations of prediction equations were obtained from L, W, product of LW and dry mass of leaves (DM) to create linear (y = a + bx), quadratic (y = a + bx + cx2), exponential (y = aebx), logarithmic (y = a + bLnx), and power models (y = axb) for each genotype. Data for all four genotypes were pooled and compared with earlier models by graphical procedures and statistical measures viz. Mean Square Error (MSE) and Prediction Sum of Squares (PRESS). A linear model having LW as the independent variables (y = -3.4444 + 0.729 LW) provided the most accurate estimate (R 2 = 0.99, MSE = 50.05, PRESS = 12.51) of clary sage leaf area. Validation of the regression model using the data from another experiment showed that the correlation between measured and predicted values was very high (R 2 = 0.98) with low MSE (107.74) and PRESS (26.96). and R. Kumar, S. Sharma.
The ultrastructure of cotton leaves, exhibiting reddening as symptom of physiological disorder, was examined by means of transmission electron microscopy. Osmiophilisation of the membrane compartment was established. Massive agglomerations on the tonoplast in the vacuole of cells under the adaxial epidermis were observed, and were referred to as electron-dense osmiophilic substance, most probably of anthocyanin nature. In chloroplast stroma a zone of low electron density enclosing numerous osmiophilic aggregations of unclear chemical character was differentiated. Fragmentation and severe destruction of thylakoids in chloroplasts of reddening cotton leaves was not detected. and D. Stoyanova-Koleva ... [et al.].
To examine the hypothesis that stomatal behavior of plants in dry soil is influenced by a slow recovery from daytime water deficit, we studied the effect of repeated wetting of leaves during evening and night in Cryptomeria japonica seedlings grown in dry soil. After 7 and 10 days of leaf wetting treatment the midday leaf water potential decreased and the transpiration rate increased, respectively. Therefore, we suggest that rapid recovery from daytime water deficit could weaken the water conserving stomatal behavior that adapts to drought conditions in the roots. and T. Tange ... [et al.].
Photosynthetic activity of leaf disks from chlortoluron (2 µmol per plant) treated and non-treated non-transgenic and transgenic (PGF-6) tobacco plants was measured from 1 up to 21 d after treatment under greenhouse conditions. PGF-6 plants, expressing the fused rat cytochrome P4501A1/yeast reductase genes were used. PGF-6 plants were much more chlortoluron-resistant than control plants. In non-transgenic tobacco plants the electron transport flow to PQ pool was strongly inhibited 1 d after treatment with herbicide whereas it was still existing in PGF-6 plants although some reduction was observed. The quantum yield of photosystem 2 (ΦPS2) which is related to the quantum yield of whole-chain electron transfer was much more inhibited by chlortoluron than the primary PS2 photochemistry, measured by the ratio Fv/Fm. Lower PS2 activity was found for herbicide-treated non-transgenic plants up to the 9th day. Then it started to increase in both control and PGF-6 plants, but more rapidly in PGF-6 ones, and its values were near to the control level at the 21st d after chlortoluron treatment. and E. Yordanova ... [et al.].
Sodium chloride (NaCl) concentratíons 200 to 900 mM enhanced the photosynthetic rate (Pn) both in whole leaves and in mechanically isolated, intact mesophyll cells of a salt marsh halophyte Sesuvium portulacastrum wilh a maximum at 600 mM NaCl. These changes were in agreement with changes in chlorophyll concentration in leaves. Though the increasing salt concentratíons resulted in leaf succulence, no change in the photosynthetic carbon pathway was observed.
Field studies with segregating populations under short days showed a significant positive correlation between tuber yield and the light-saturated net photosynthetic rate (Fn) in the 4th leaf from the top, at the tuber formation stage, in two seasons. The leaf area per plant {A) at this stage and also at the tuber bulking stage had a significant positive correlation with tuber yield. The product of PN and A also showed a significant positive correlation with tuber yield at both of these stages, a stronger one than that between tuber yield and A at the tuber formation stage.