Excess solar radiation under hot climate can lead to decline in photosynthetic activity with detrimental effects on growth and yield. The aim of this study was to evaluate the use of a transparent plastic roof as shading for diurnal changes in photosynthetic gas exchange, chlorophyll fluorescence, fruit set and quality of mango (Mangifera indica L.) cv. 'Nam Dok Mai' growth in the field conditions. Fully expanded leaves were examined either shaded by the plastic roof or sunlit under natural conditions. Leaf temperature and leaf-to-air vapour pressure deficit of the shaded leaves measured on the clear day were lowered compared to those of the sunlit leaves. It resulted in increased stomatal conductance and photosynthetic rates of the shaded leaves compared to those of the sunlit leaves, especially from the morning to midday. Furthermore, the reversible decrease of the maximal quantum yield of PSII was more pronounced in the sunlit leaves than that in the shaded ones. Shading increased the total fruit number; the shaded fruits developed better external color than that of the sun-exposed fruits. Our results indicated that shading could maintain the high photosynthetic activity by reducing stomatal limitations for carbon supply and was effective in alleviating the photoinhibitory damage to PSII during bright and clear days with excessive radiation. Finally, shading could increase the number of fruits and improve mango peel color., K. Jutamanee, S. Onnom., and Obsahuje bibliografii
The intenzity of illumination of a solar panel depends on the angle between its normal and the direction of the solar beam and it can be, consequently, enhanced for the panel tracked towards the sun. The aim of the paper is to compare the intensity of illumination of the fixed (non-tracking) panel and illumination of the panel with one or two tracking axes. The annual irradiation and irradiation in individual months was determined using the coefficient of contamination Z = 4 characterizing the atmosphere in towns. The data of the sun elevation and azimuth during one year for the latitude 50° N were utilized for the calculation. and Intenzita ozáření slunečního panelu závisí na úhlu, který svírá jeho normála se směrem slunečních paprsků a může se proto zvýšit, bude-li se panel natáčet za sluncem. Cílem této práce je porovnat intenzitu ozáření pevného (nenatáčeného) panelu a panelu natáčeného za sluncem kolem jedné, případně dvou os. Byla určena iradiace panelu za celý rok i pro jednotlivé měsíce při koeficientu znečištění atmosféry Z = 4, který charakterizuje atmosféru ve městech. Pro výpočet byla využita data výšky slunce nad obzorem a azimutu v průběhu roku pro 50. stupeň severní šířky.