This study developed a method for estimating the leaf area (LA) of muskmelon by using allometry. The best linear measure was evaluated first, testing both a leaf length and width (W). Leaf samples were collected from plants grown in containers of different sizes, leaves of four cultivars, at different develpoment stages, and of different leaf sizes. Two constants of a power equation were determined for relating allometrically a linear leaf measure and LA, in a greenhouse crop. W proved to be a better fit than the leaf length. The maximum attainable W and LA were estimated at Wx = 15.4 cm and LAx = 174.1 cm2. The indicators of fit quality showed that the function was properly related to LA and W as: LA/LAx = Ao × (W/WLx)b; the allometric exponent was b = 1.89, where R 2 = 0.9809 (n = 484), the absolute sum of squares, 0.4584, and the standard deviation of residues, 0.03084, based on relative values calculations (LA/LA x and W/WLx). The relationship was not affected by the cultivar, crop age, leaf size or stress treatment in the seedling stage. The empirical value of allometric constant (A0) was estimated as 0.963. and E. Misle ... [et al.].
Simple, accurate, and non-destructive methods for determining leaf area (LA) of plants are important for many experimental comparisons. Determining the individual LA of sunflower (Helianthus annuus L.) involves measurements of leaf parameters such as length (L) and width (W), or some combinations of these parameters. Two field experiments were carried out during 2003 and 2004 to compare predictive equations of sunflower LAs using simple linear measurements. Regression analyses of LA vs. L and W revealed several equations that could be used for estimating the area of individual sunflower leaves. A linear equation having W2 as the independent variable provided the most accurate estimate (r 2 = 0.98, MSE = 985) of sunflower LA. Validation of the equation having W2 of leaves measured in the 2004 experiment showed that the correlation between calculated and measured areas was very high. and Y. Rouphael ... [et al.].
This study measured individual leaf area expansion rate and leaf net photosynthetic rate (PN) of meadow bromegrass (Bromus riparius Rehm.), smooth bromegrass (Bromus inermis Leyss.) and hybrid bromegrass (B. riparius × B. inermis). Smooth bromegrass expanded individual leaf area 1.5 times faster than meadow bromegrass and hybrid bromegrass. PN was highest in smooth bromegrass, intermediate in hybrid bromegrass, and lowest in meadow bromegrass. Rapid growth of meadow bromegrass following defoliation compared to smooth bromegrass and hybrid bromegrass could not be explained by higher rates of these measured characteristics. and B. Biligetu, B. Coulman
Leaf area is one of the most important parameter for plant growth. Reliable equations were offered to predict leaf area for Zea mays L. cultivars. All equations produced for leaf area were derived as affected by leaf length and leaf width. As a result of ANOVA and multiregression analysis, it was found that there was a close relationship between actual and predicted growth parameters. The produced leaf-area prediction model in the present study is LA =
a + b L + c W + d LZ where LA is leaf area, L is leaf length, W is maximum leaf width, LZ is leaf zone and a, b, c, d are coefficients.
R2 values were between 0.88-0.97 and standard errors were found to be significant at the p<0.001 significance level. and F. Oner ... [et al.].
In two successive years (2003 and 2004), a set of 16 commercial sugar beet cultivars was established in Randomized Complete Block experiments at two sites in central Greece. Cultivar combination was different between years, but not between sites. Leaf sampling took place once during the growing season and leaf area, LA [cm2], leaf midvein length, L [cm] and maximum leaf width, W [cm] were determined using an image analysis system. Leaf parameters were mainly affected by cultivars. Leaf dimensions and their squares (L2, W2) did not provide an accurate model for LA predictions. Using L×W as an independent variable, a quadratic model (y = 0.003 x2 - 1.3027 x + 296.84, r 2 = 0.970, p<0.001, n = 32) provided the most accurate estimation of LA. With compromises in accuracy, the linear relationship between L×W and LA (y = 0.5083 x + 31.928, r 2 = 0.948, p<0.001, n = 32) could be used as a prediction model thanks to its simplicity. and J. T. Tsialtas, N. Maslaris.
In six dominant species of the Amazonian 'Bana' vegetation, leaf blade characteristics, pigment composition, and chlorophyll (Chl) fluorescence parameters were measured in young and mature leaves under field conditions. Leaf δ13C was comparable in the six species, which suggested that both expanding and expanded leaves contained organic matter fixed under similar intercellular and ambient CO2 concentration (Ci/Ca). High leaf C/N and negative δ15N values found in this habitat were consistent with the extreme soil N-deficiency. Analysis of Chl and carotenoids showed that expanding leaves had an incomplete development of photosynthetic antenna when compared to adult leaves. Dynamic inactivation of photosystem 2 (PS2) at midday was observed at both leaf ages as Fv/Fm decreased compared to predawn values. Adult leaves reached overnight Fv/Fm ratios typical of healthy leaves. Overnight recovery of Fv/Fm in expanding leaves was incomplete. F0 remained unchanged from midday to predawn and Fv tended to increase from midday to predawn. The recovery from midday depression observed in adult leaves suggested an acclimatory down-regulation associated with photo-protection and non-damage of PS2.
Under constant salinity we analysed the leaf characteristics of Laguncularia racemosa (L.) Gaertn. in combination with gas exchange and carbon isotopic composition to estimate leaf water-use efficiency (WUE) and potential nitrogen-use efficiency (NUE). NaCl was not added to the control plants and the others were maintained at salinities of 15 and 30 ‰ (S0, S15, and S30, respectively). Leaf succulence, sodium (Na), nitrogen (N), and chlorophyll (Chl) contents increased under salinity. Salinity had a negative impact on net photosynthetic rate (PN) and stomatal conductance (gs) at high and moderated irradiances. Potential NUE declined significantly (p<0.05) with salinity by 37 and 58 % at S15 and S30, respectively, compared to S0 plants. Conversely, compared to S0 plants, PN/gs increased under saline conditions by 12 % (S15) and 50 % (S30). Thus, WUE inferred from PN/gs was consistent with salinity improved short-term WUE. Long-term leaf WUE was also enhanced by salinity as suggested by significantly increased leaf δ13C with salinity. Improved WUE under salinity explains the eco-physiological success of mangrove species under increasing salinity. Conversely, decline in NUE may pose a problem for L. racemosa under hyper-saline environments regardless of N availability.
Leaf chloroplast ultrastructure and photosynthetic properties of a natural, yellow-green leaf mutant (ygl1) of rice were characterized. Our results showed that chloroplast development was significantly delayed in the mutant leaves compared with the wild-type rice (WT). As leaves matured, more grana stacks formed concurrently with increasing leaf chlorophyll (Chl) content. Except for the lower intercellular CO2 concentration, the ygl1 plants had a higher leaf net photosynthetic rate, stomatal conductance, and transpiration rate than those of the WT plants. Under equal amounts of Chl, the excitation energy of PSI and PSII was much stronger in the mutant than that in the WT. The ygl1 plants showed higher nonphotochemical quenching and lower photochemical quenching. They also exhibited higher actual photochemical efficiency of PSII with a higher electron transport rate. Under the light of 200 μmol(photon) m-2 s-1, the ygl1 mutant showed lesser deepoxidation of violaxanthin in the xanthophyll cycle than WT, but it increased substantially under strong light conditions. In conclusion, the photosynthetic machinery of the ygl1 remained stable during leaf development. The plants were less sensitive to photoinhibition compared with WT due to the active xanthophyll cycle. The ygl1 plants were efficient in both light harvesting and conversion of solar energy., Z. M. Wu, X. Zhang, J. L. Wang, J. M. Wan., and Obsahuje bibliografii
Drought significantly constrains higher yield of alfalfa (Medicago sativa L.) in arid and semiarid areas all over the world. This study evaluated the responses of leaf cuticular wax constituents to drought treatment and their relations to gas-exchange indexes across six alfalfa cultivars widely grown in China. Water deficit was imposed by withholding water for 12 d during branching stage. Cuticular waxes on alfalfa leaves were dominated by primary alcohols (41.7-54.2%), alkanes (13.2-26.9%) and terpenes (17.5-28.9%), with small amount of aldehydes (1.4-3.4%) and unknown constituents (4.5-18.4%). Compared to total wax contents, the wax constituents were more sensitive to drought treatment. Drought decreased the contents of primary alcohol and increased alkanes in all cultivars. Alkane homologs, C25, C27, and C29, were all negatively correlated with photosynthetic rate, transpiration rate, stomatal conductance, and leaf water potential. Under drought conditions, both stomatal and nonstomatal factors were involved in controlling water loss from alfalfa leaves. No direct relationship was observed between wax contents and drought resistance among alfalfa cultivars. An increase in alkane content might be more important in improving drought tolerance of alfalfa under water deficit, which might be used as an index for selecting and breeding drought resistant cultivars of alfalfa., Y. Ni ... [et al.]., and Obsahuje bibliografii
Leaf developmental patterns were characterized for three tropical tree species with delayed greening. Changes in the pigment contents, photosynthetic capacity, stomata development, photosystem 2 efficiency, rate of energy dissipation, and the activity of partial protective enzymes were followed in developing leaves in an attempt to elucidate the relative importance of various photoprotective mechanisms during leaf ontogeny. Big leaves of Anthocephalus chinensis, a fast-growing light demanding species, expanded following an exponential pattern, while relatively small leaves of two shade-tolerant species Litsea pierrei and Litsea dilleniifolia followed a sigmoidal pattern. The juvenile leaves of A. chinensis and L. pierrei contained anthocyanin located below the upper epidermis, while L. dilleniifolia did not contain anthocyanin. Leaves of A. chinensis required about 12 d for full leaf expansion (FLE) and photosynthetic development was delayed 4 d, while L. pierrei and L. dilleniifolia required 18 or 25 d for FLE and photosynthetic development was delayed 10 or 15 d, respectively. During the leaf development the increase in maximum net photosynthetic rate was significantly related to changes in stomatal conductance and the leaf maturation period was positively related to the steady-state leaf dry mass per area for the three studied species. Dark respiration rate of leaves at developing stages was greater, and pre-dawn initial photochemical efficiency was lower than that of mature leaves. Young leaves displayed greater energy dissipation than mature leaves, but nevertheless, the diurnal photoinhibition of young L. dilleniifolia leaves was higher than that of mature leaves. The young red leaves of A. chinensis and L. pierrei with high anthocyanin contents and similar diurnal photoinhibition contained more protective enzymes (superoxide dismutase, ascorbate peroxidase) than mature leaves. Consequently, red leaves may have higher antioxidant ability. and Z. Q. Cai, M. Slot, Z. X. Fan.