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[en] Evapotranspiration is one of the crucial components of hydrological cycle. The Penman-Monteith method (PM) is recommended as the sole standard method for estimating reference evapotranspiration (ET0). The usage of the PM method is limited in many regions due to the lack of required weather data. In such circumstances, simple Thornthwaite equation is often used to estimate ET0. The main objectives of the present study are (i) to estimate reference evapotranspiration using different Thornthwaite approaches, (ii) to develop optimal adjusted equation, and (iii) to consider the spatial variability of the empirical coefficient(s) of adjusted equation for the study area. In this study, six Thornthwaite approaches were compared to the full set PM equation using weather data from Vojvodina region, Serbia. The original Thornthwaite equation was very poor in estimating ET0 and greatly underestimated PM values at all locations. It can be concluded that an adjustment of the Thornthwaite equation is necessary. The obtained results indicate that ET0 could be estimated from the new Th65 approach (effective temperature, k = 0.65), which reproduced statistical characteristics better compared to other Thornthwaite approaches. The spatial variability of the empirical k coefficient showed that k values varied from 0.62 to 0.69 across the study area with deviations of − 5% to 6% compared to a unique k value of 0.65. These results suggested that single regional k value can be successfully used for estimating ET0.
[en] The data of photosynthetic activity and stomatic aperture of bean-seedlings leaves, and the relations obtained with both results are showed. It has been observed that the product of photosynthetic activity by the resistance to transpiration measured by a porosimeter is a constant, between some limits. (author)
[en] Highlights: → We measured vapor pressure of diamines H2N-(CH2)n-NH2 with n = 3 to 12. → Vaporization enthalpies at 298 K were derived. → We examined consistency of new and available in the literature data. → Enthalpies of vaporization show linear dependence on numbers n. → Enthalpies of vaporization correlate linearly with Kovat's indices. - Abstract: Vapor pressures and the molar enthalpies of vaporization of the linear aliphatic alkanediamines H2N-(CH2)n-NH2 with n = (3 to 12) have been determined using the transpiration method. A linear correlation of enthalpies of vaporization (at T = 298.15 K) of the alkanediamines with the number n and with the Kovat's indices has been found, proving the internal consistency of the measured data.
[en] The present paper contains the data of photosynthetic activity and stomatic aperture of bean-seedlings Ieaves, and the relations obtained with both results. It has been observed that the product of photosynthetic activity by the resistance; to transpiration measured by a promoter ia a constant, between some limits. (Author) 45 refs
[en] Accumulation of o-chlorophenol (CP), 2,4-dichlorophenol (DCP), and atrazine (ATR), as single and mixed contaminants, from hydroponic solutions into roots and shoots of rice seedlings was studied following 48-h exposure of the plant roots. As single contaminants at low levels, the observed bioconcentration factors (BCFs) of CP and DCP with roots approximated the equilibrium values according to the partition-limited model. The BCF of atrazine with roots was about half the partition limit for unknown reasons. The BCFs of CP and ATR with shoots also approximated the partition limits, while the BCF for more lipophilic DCP with shoots was about half the estimated limit, due to insufficient water transport into plants for DCP. As mixed contaminants at low levels, the BCFs with both roots and shoots were comparable with those for the single contaminants; at high levels, the BCFs generally decreased because of the enhanced mixed-contaminant phytotoxicity, as manifested by the greatly reduced plant transpiration rate. - Uptakes of o-chlorophenol, 2,4-dichlorophenol, and atrazine at various levels from nutrient solution by roots and shoots of rice seedlings were investigated using a partition-limited model
[en] The combined effects of elevated carbon dioxide concentration and defoliation on the growth and physiology of sugar maple and trembling aspen are examined. After removal of half the leaf area from seedlings grown in eight open-top chambers for six weeks, seedlings in four chambers were ventilated in carbon dioxide-enriched air and four chambers were supplied with ambient air. Subsequent biomass gains and allocations were monitored, along with leaf gas exchange and chemistry. Elevated carbon dioxide had no significant effect on aspen growth and observed stimulation of growth in maple seedlings was not evident until mid-season. Significant interaction between carbon dioxide and defoliation was confined to only a few of the measured traits. Thus, the data obtained do not support the hypothesis that atmospheric carbon dioxide enrichment will substantially alter tree responses to defoliation. 82 refs., 4 tabs., 6 figs