Correlation Analysis of Transpiration Rate in Eggplant Canopy: Effects of Solar Radiation and Vapor Pressure Deficit

Temporal variations of carbon and water fluxes in a subtropical mangrove forest: Insights from a decade-long eddy covariance measurement

We assessed in absolute and relative terms how solar radiation and water vapour pressure deficit control the latent heat flux density in a Scots pine (Pinus sylvestris L.) forest growing under boreal conditions. The absolute and relative total control can be expressed as sums of the physical and biological forms of control. Physical control is based on the direct effects of solar radiation and water vapour pressure deficit on latent heat flux density, and biological control on the effects of solar radiation and water vapour pressure deficit on latent heat flux density through surface resistance. Measurements based on the eddy covariance method were used in the assessment, which defined the scale adopted in the study. Relative physical control over latent heat flux density was mainly exercised by water vapour pressure deficit, and the role of solar radiation was only marginal. The relative biological control exercised by solar radiation over latent heat flux density was higher in the morning and afternoon, unlike the control exercised by water vapour pressure deficit, which was strongest around noon. The values for the relative total control exercised by solar radiation over latent heat flux density were in general higher than those for relative total control exercised by water vapour pressure deficit. This is inconsistent with expectations based on Omega theory, where a decoupling coefficient (Ω) indicates the relative control exercised by surface resistance over latent heat flux density. Solar radiation and water vapour pressure deficit do not necessarily act in opposite directions in the absolute or relative total control that they maintain over latent heat flux density.

It was clarified in the previous papers that leaf water potential, stomatal aperture and photosynthetic rate in rice plants decreased with increase in solar radiation and vapor pressure deficit even though rice plants grew under the condition where sufficient water was supplied to roots in submerged paddy field, and that the decrease in leaf water potential, stomatal aperture and photosynthetic rate were more remarkable in rice plants with low root activity or with poor root system. The present study was conducted to investigate the relationship between water uptake and transpiration rates and the effects of this relation on leaf water potential and stomatal aperture through their diurnal changes, and to discuss the characteristics for maintaining water balance in rice plants. Transpiration rate was higher than water uptake rate in the morning when transpiration was increasing rapidly with rapid increase in solar radiation and vapor pressure deficit. Both rates were practically the same in the midday and then transpiration rate was lower than water uptake rate in the evening when transpiration rate was decreasing rapidly with rapid decrease in solar radiation and vapor pressure deficit (Fig. 2 A). The difference between water uptake and transpiration rates was very small even when transpiration rate was changing rapidly (Fig. 2 B). In case of reduced water uptake due to low water potential of culture solution or NaN3 treatment to roots, transpiration rate decreased remarkably due to increase of stomatal closure in the daytime (Figs. 3 and 4). Therefore, the difference between water uptake and transpiration rates did not increase so much and leaf water potential decreased a very little even in the midday with high transpiration demand compared with decrease of water uptake rate and stomatal aperture (Figs. 3 and 4). These results suggested that water balance in rice plants was maintained by the process as follows: There is too much transpiration in the daytime with high solar radiation and valor pressure deficit, so water uptake could not overtake the transpiration, and leaf water potential decreased to a certain extent. As stomata in rice plants were very sensitive to change of leaf water potential compared with those of other plants, stomata closed very rapidly with response to the decrease of water potential, so that transpiration rate decreased to almost the same as water uptake. Therefore, the difference between water uptake and transpiration rates was very small, and decrease of leaf water potential was prevented. Futhermore, in case of rice plants with reduced water uptake due to low water potential of culture solution or NaN3 treatment to roots, all were the same as in the process of maintaining water balance. From these results and the high correlation between stomatal aperture and photosynthetic rate, it was considered that water uptake ability directly affected photosynthetic rate under sufficient solar radiation in rice plants with stomata responding very sensitively to change of leaf water potential. Futhermore, it was suggested that rapid wilting often observed in rice, soybean and cucumber under very large vapor pressure deficit or on water saturated soil in rainy season, baiu, could arise from both decrease of water uptake ablility and loss of sensitivity of stomata to decrease of leaf water potential.

Quantitative information regarding biomass accumulation and partitioning in chickpea (Cicer arietinum L.) is limited or inconclusive. The objective of this study was to obtain baseline values for extinction coefficient (KS), radiation use efficiency (RUE, g MJ−1) and biomass partitioning coefficients of chickpea crops grown under well‐watered conditions. The stability of these parameters during the crop life cycle and under different environmental and growth conditions, caused by season and sowing date and density, were also evaluated. Two field experiments, each with three sowing dates and four plant densities, were conducted during 2002–2004. Crop leaf area index, light interception and crop biomass were measured between emergence and maturity. A KS value of 0.5 was obtained. An average RUE of 1 g MJ−1 was obtained. Plant density had no effect on RUE, but some effects of temperature were detected. There was no effect of solar radiation or vapour pressure deficit on RUE when RUE values were corrected for the effect of temperature. RUE was constant during the whole crop cycle. A biphasic pattern was found for biomass partitioning between leaves and stems before first‐seed stage. At lower levels of total dry matter, 54 % of biomass produced was allocated to leaves, but at higher levels of total dry matter, i.e. under favourable and prolonged conditions for vegetative growth, this portion decreased to 28 %. During the period from first‐pod to first‐seed, 60 % of biomass produced went to stems, 27 % to pods and 13 % to leaves. During the period from first‐seed to maturity, 83 % of biomass was partitioned to pods. It was concluded that using fixed partitioning coefficients after first‐seed are not as effective as they are before this stage. Environmental conditions (temperature and solar radiation) and plant density did not affect partitioning of biomass.

Flower opening in the early morning helps to avoid sterility of rice (Oryza sativa L.) caused by heat stress at anthesis. Although flower opening time (FOT) is under genetic control, it is also affected by weather, particularly by air temperature (Ta). However, the effects of Ta, solar radiation (Rs), and vapor-pressure deficit (VPD) on rice FOT are unclear, making it difficult to predict FOT. Therefore, we investigated the correlation of FOT with Ta, Rs, and VPD during various periods before anthesis under field conditions. By photographing spikelets at 10-min intervals, we determined the FOT of five cultivars. To evaluate the individual effects of cultivar, Ta, Rs, and VPD on FOT, we constructed general linear models (GLMs) and calculated mean Ta, R s, and VPD every 3 hr from 0000 to 1200. The GLMs revealed that the average Ta, Rs, and VPD between 0600 and 0900 significantly affected FOT (adjusted R 2 =0.399; P <0.001). The standardized partial regression coefficients of Ta and Rs were negative and those of VPD were positive, indicating that higher Ta, higher Rs, and lower VPD in the early morning result in earlier FOT. Moreover, multiple-regression analysis showed that the period affecting FOT the most, and the relative contributions of Ta, Rs, and VPD to FOT differ with the cultivar.

ソルガムを窒素施用量と土壌水分含量ならびに日射量と土壌水分含量を複合的に変えた育苗箱条件下で栽培し, 土壌水分に対するソルガムの初期生育反応に及ぼす窒素施用量と日射量の影響について調査した.ソルガムの生育に対して基本的に土壌水分含量は生長促進作用としての線形要因的性格と阻害作用としての逆数要因的性格とを併せ持つ両性要因として作用するが, 最適土壌水分含量未満の範囲においては土壌水分の過剰による生育抑制項を欠いた逆数式で対応できた.窒素施用量は低土壌水分条件下では両性要因として作用したが土壌水分含量の増大に伴って逆数要因的特性が不明確となった.これらの関係は, 1/〓W=A/(f-f0)+B(g+g0)/(f-f0)+C/[(f-f0)(g+g0)]+D/(g+g0)+Eで近似できた.ここで, 〓W, fおよびgはそれぞれ全乾物増加量, 土壌水分含量, 窒素施用量, f0とg0は非有効土壌水分含量の上限値と土壌および種子からの窒素持ち込み量, またA, B, C, DとEは係数である.日射量は生育量に対して線形要因として作用し, 土壌水分含量と日射量を変えた複合条件下におけるソルガムの生育量は, 1/〓W=A/(S-S0)+B/(f-f0)+C(f-f0)+Dで近似できた.ここで, SとS0は日射量と日補償点である.以上の結果は, 日射量と土壌水分含量の影響はそれぞれ単独効果の和として表せるのに対して, 窒素施用量と土壌水分含量の複合条件下では両要因の交互作用効果が無視できないことを示している。また, 蒸散効率に対する土壌水分含量, 窒素施用量および日射量の影響は大きくないと考えられた.

The plant water or nutrient requirement under greenhouse conditions is mainly governed by crop transpiration in a linear relation to vapour pressure deficit (VPD), particularly in soilless production systems. Being a cooling process in plants, transpiration governs the plant water requirement in relation to the subjected microclimatic conditions and VPD can be used as a tool to maintain greenhouse crop transpiration to optimal range for obtaining desired crop yields. Thus, the present investigation was undertaken to study the integrated effect of temperature (Tapc), relative humidity (Eapc) and solar radiation (Irad) on VPD and crop transpiration. A computer module was developed to monitor the behavior of the VPD and thereby the crop transpiration through charts under greenhouse conditions. The VPD indicated a linear increasing trend with Tapc (R2≥0.84) and decreasing trend with Eapc (R2=0.99), demonstrating a strong correlation in both cases. The increasing crop transpiration with VPD, particularly under hot climatic conditions significantly increased the input water and nutrient requirements of the crop. Thus, transpiration in relation to VPD should be considered as a factor for fertigation scheduling and improving irrigation control in soilless systems. Moreover, maintaining Tapc, Eapc and VPD within range of 22-27°C, 60-80% and 0.53-1.10 kPa may help to control the crop transpiration, manage the greenhouse irrigation and fertigation, and thus improve the cucumber yield.

The effect of climate on tomato transpiration in greenhouses: measurements and models comparison

Growing yellow cattle (Bos taurus, n 30, 1.0-3.5 years old and 75-240 kg) from their native altitude (2000-2800 m) were used to evaluate the effects of altitude, ambient temperature (Ta) and solar radiation on the basal energy metabolism in this large mammal. Fasting heat production (FHP) was measured at altitudes of 2260, 3250 and 4270 m on the Tibetan plateau both in the summer and winter respectively, after a 90 d adaptation period at each experimental site. The gas exchanges of the whole animal were determined continuously for 3 (2260 and 3250 m) or 2 (4270 m) d after a 96 (2260 and 3250 m) or 48 (4270 m) h starvation period, using closed-circuit respiratory masks. Increasing altitude from 2260 to 3250 m at similar Ta in the summer significantly elevated FHP for all animals (P<0.01), and from 3250 to 4270 m for young cattle (P<0.05); increasing altitude from 2260 to 3250 m in the winter also significantly elevated FHP (P<0.05), but the increase was mainly due to the decrease of Ta and the increase in wind speed. No results were obtained at 4270 m in the winter, due to the problems of the animals, adapting to the altitude. The magnitude of FHP elevation caused by increasing altitude was greater with summer sunshine or winter wind than without them. Increase of Ta from 10.0 to 22.0 degrees C, in the presence of solar radiation, slightly (2260 m) or significantly (3250 and 4270 m, P<0.01) elevated FHP, but slightly reduced it in the absence of solar radiation; decrease of Ta from 0.0 to -30.0 degrees C linearly increased FHP. At 3250 and 4270 m, FHP at the same Ta was higher with summer sunshine or winter wind (3250 m) than without them, but this did not occur at 2260 m. In conclusion, high altitude elevates FHP in yellow cattle in the warm season, and the summer solar radiation and winter wind at high altitude significantly increase metabolic rate. It may be also concluded that the effects of solar radiation on metabolic rate depend on the altitude and the environmental temperature.

The effect of solar radiation on collagen and collagen/synthetic polymer blends in the form of thin films and solutions has been studied by UV‐VIS and FTIR spectroscopies. Films and solutions of collagen blended with poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were irradiated by solar light. It was found that UV‐VIS spectra, which characterize collagen, collagen/PVA, and collagen/PVP blended films, were significantly altered by solar radiation. FTIR spectra of collagen, collagen/PVA, and collagen/PVP films showed that after solar irradiation, the positions of Amide A bands were shifted to lower wavenumbers. There was not any significant alteration in the position of Amide I and Amide II bands of collagen and its blends after solar radiation. The effect of solar UV radiation in comparison with artificial UV radiation has been discussed.

Effects of solar radiation on collagen and chitosan films

This work presents both analytical and experimental results of the effect of unfiltered natural solar radiation on the thermal and dynamic mechanical properties of Boran bovine leather at both pickling and tanning stages of preparation. Samples cut from both pickled and tanned pieces of leather of appropriate dimensions were exposed to unfiltered natural solar radiation for time intervals ranging from 0 h (non-irradiated) to 24 h. The temperature of the dynamic mechanical analyzer was equilibrated at \(30\, ^\circ \hbox {C}\) and increased to \(240\, ^\circ \hbox {C}\) at a heating rate of \(5\,^\circ \hbox {C}\cdot \hbox {Min}^{-1}\), while its oscillation frequency varied from 0.1 Hz to 100 Hz. With the help of thermal analysis (TA) control software which analyzes and generates parameter means/averages at temperature/frequency range, the graphs were created by Microsoft Excel 2013 from the means. The viscoelastic properties showed linear frequency dependence within 0.1 Hz to 30 Hz followed by negligible frequency dependence above 30 Hz. Storage modulus (\(E'\)) and shear stress (\(\sigma )\) increased with frequency, while loss modulus (\(E''\)), complex viscosity (\(\eta ^{*}\)) and dynamic shear viscosity (\(\upeta )\) decreased linearly with frequency. The effect of solar radiation was evident as the properties increased initially from 0 h to 6 h of irradiation followed by a steady decline to a minimum at 18 h before a drastic increase to a maximum at 24 h. Hence, tanning industry can consider the time duration of 24 h for sun-drying of leather to enhance the mechanical properties and hence the quality of the leather. At frequencies higher than 30 Hz, the dynamic mechanical properties are independent of the frequency. The frequency of 30 Hz was observed to be a critical value in the behavior in the mechanical properties of bovine hide.

Objective To investigate solar radiation and its effects on human tooth enamel electron spin resonance (ESR) dosimetry. Methods 11 tooth enamel samples were prepared by mechanical method. The intensity of solar iUuminanee was measured with a light meter, the measured illuminance was converted to insolation using a coefficient. Summation of solar radiation was evaluated. Enamel samples were exposed to 60 Co γ rays followed by sunlight on sunny days, and ESR spectra were scanned after different exposure. Results The solar radiation to the samples was (580 ± 16) MJ/m2. Solar exposure also caused dosimetrie signal. The perpendicular component of dosimetrie signal increased linearly with the amount of solar radiation, another signal close to background tended to saturation. Conclusions The average effect of the solar radiation on the signal was be used to recognize the effect of solar radiation on the enamel, and estimate external dose accurately. Key words: Solar illuminance; Solar radiation; Tooth enamel; Electron spin resonance; Dosimetry

ABSTRACTCowhide, a natural biopolymer of collagen, forms raw material for leather, biomaterials, and food, among others. Thermal and mechanical analysis was done using dynamic mechanical analyzer. Effect of tanning and natural solar radiations on the storage modulus, tan δ, and thermal stability of pickled and tanned cowhides has been investigated in the temperature range of 30–240°C. Tanning has been shown to enhance thermal stability and storage modulus. However, tanning decreases its dissipative capability. Thermal stability of both tanned and pickled hide decreased with time of exposure to irradiation. Storage modulus dropped drastically within the initial 6 h of natural solar radiations before rising progressively with the subsequent 12, 18, and 24 h, although still lower than that for nonirradiated sample. Thermal–mechanical analysis proved to be a useful technique for assessing effect of tanning and natural solar radiations on cowhide. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43208.

Amazon forests play an important role in the global carbon cycle and Earth’s climate. The vulnerability of Amazon forests to drought remains highly controversial. Here we examine the impacts of the 2015 drought on the photosynthesis of Amazon forests to understand how solar radiation and precipitation jointly control forest photosynthesis during the severe drought. We use a variety of gridded vegetation and climate datasets, including solar-induced chlorophyll fluorescence (SIF), photosynthetic active radiation (PAR), the fraction of absorbed PAR (APAR), leaf area index (LAI), precipitation, soil moisture, cloud cover, and vapor pressure deficit (VPD) in our analysis. Satellite-derived SIF observations provide a direct diagnosis of plant photosynthesis from space. The decomposition of SIF to SIF yield (SIFyield) and APAR (the product of PAR and fPAR) reveals the relative effects of precipitation and solar radiation on photosynthesis. We found that the drought significantly reduced SIFyield, the emitted SIF per photon absorbed. The higher APAR resulting from lower cloud cover and higher LAI partly offset the negative effects of water stress on the photosynthesis of Amazon forests, leading to a smaller reduction in SIF than in SIFyield and precipitation. We further found that SIFyield anomalies were more sensitive to precipitation and VPD anomalies in the southern regions of the Amazon than in the central and northern regions. Our findings shed light on the relative and combined effects of precipitation and solar radiation on photosynthesis, and can improve our understanding of the responses of Amazon forests to drought.