Light is one of the main factors regulating plant growth and development. Among different aspects of Light, its intensity has a great effect on plant responses, such as plant's water relations. The aim of this study was to evaluate the effect of Light intensity on performance, evapotranspiration and water use efficiency of lettuce (Lactuca sativa cv. par tavousi) in a completely randomized design with four treatments and twelve replications in the Park of Science and Technology in Aburaihan campus of Tehran University. The present experiment was done by using spectra composition of red and blue (as the main wavebands on growth and gas relations) with a ratio of 70 and 30 %, respectively with four intensities including (T1) 75, (T2) 150, (T3) 300 and (T4) 600 μ mol. m-2. S-1. The studied traits included growth characteristics associated with water use efficiency. Based on the results, the highest fresh weight (73. 52 g) was obtained from T3 and the lowest fresh weight (17. 31 g) was obtained under Light intensity T3, respectively. Any Light intensity increasing caused an increasing in dry weight and leaf area. The highest growth simulation was observed under T3. Furthermore, the highest and the lowest water use efficiencies were observed in plants that were grown under T4 and T1.

Research Problem: The development of modern technologies has become a global common infrastructure and priority due to its environmental, economic and social advantages. Due to the increase in population and expansion of the man-made environment and turning to architecture and interior design, the demand for energy for various purposes is increasing day by day. Therefore, the intelligent use of renewable energy plays an important role in improving the sustainability and energy efficiency in architectural design. Research Question: What effect does the geometry of the window and the use of optical shelves have on the reception and optimal use of natural Light? Research Method: The purpose of the present research is the feasibility of using new technologies, including optical racks, in architectural design, emphasizing the approach of increasing the efficiency of renewable energy (sunLight) in Arian Tower, Hamedan.  Research method: Applied research has a quantitative nature and data analysis method is combined, descriptive-analytical and simulation. Collecting information is done by field surveys in the space of Aryan Tower and collecting data with devices such as lux meters. By using Design Builder and Ecotect software, the role of Light shelves on providing natural Lighting in Arian Tower is investigate The Most Important Results and Conclusion: The investigations carried out on the building unit show that the internal parts of the plan do not receive any natural Light and this problem causes the increase in energy consumption. It is because the lamps are turned on to provide Lighting. By installing a Light ledge, which is one of the methods of using renewable energy, an attempt was made to bring the Light to the depth of the plan, and this system performed well in performing its task and received the Green Star certificate. Finally, it was concluded that the use of optical shelf has a significant effect in reducing the cold and heat load and especially increasing the Lighting load.

In order to evolution of radiation use efficiency (RUE) of sesame in the condition of using biological and chemical fertilizers and calculation of Light extinction coefficient (K), an experiment was conducted in the year 2013 in RCBD design with 3 replications and 10 treatments. Treatments included biological fertilizers of Nitroxin, Biophosphor, Biosulfur, the mixture of Nitroxin-Biophosphor (Ni+BP), the mixture of Nitroxin-Biophosphor-Biosulfur (Ni+BP+TB) and chemical fertilizers of Urea, Triple superphosphate, the mixture of Urea-Triple superphosphate (U+P), the mixture of Urea-Triple superphosphate-Sulfur (U+P+S) and Control. Results showed that Light extinction coefficient of 0. 7 was an acceptable value. Biological and chemical fertilizers increased leaf area index (LAI) and RUE of Sesame and generally, chemical fertilizers increased RUE more in comparison of biological fertilizers. The highest value of LAI (3. 42 and 3. 32) belonged to U+P+S and U+P. RUE values in mixture treatments of biological and chemical fertilizers especially for Ni+BP+TB and U+P+S (1. 34 and 1. 41 respectively) were greater than its values in the sole application of fertilizers. Urea increased radiation use efficiency of sesame (1. 34) more than Nitroxin (1. 14), while the amount of increase of radiation use efficiency in triple superphosphate (1. 26) and Biophosphor (1. 25) was almost identical. Therefore, it is recommended that fertilization of sesame be done by using the mixture of some different biological or chemical fertilizers in order to maximizing RUE by compliment of plant nutritional needs.

A field experiment has been carried out to study the competition between soybean and sesame in different planting ratios of intercropping based on replacement method. It is based on a randomized complete block design with four replications at Sari Agricultural Science and Natural Resources University during 2019. The planting ratios are 0: 100, 25: 75, 50: 50, 75: 25, and 100: 0 (Soybean: Sesame respectively), using replacement method. Results show that intercropping has had a significant effect on the percentage of N derived from the atmosphere and Light use efficiency. Among the different planting ratios, the maximum amount of biological nitrogen fixation is related to the 90-days after planting, and the 75: 25 and 25: 75 planting ratios have had the highest (75. 95%) and lowest activity rates (42. 67%), respectively. In addition, the highest Light use efficiency in intercropping is related to the 120-days after planting. At this stage, the Light use efficiency in 75: 25 and 50: 50 ratios are 2. 03 and 1. 92 g. MJ.-1, respectively. The highest land equivalent ratio is 50: 50, with an average of 1. 12. Finally, increasing the Light use efficiency in planting ratios of 75: 25 and 50: 50 prove to be essential in increasing soybean's biological nitrogen fixation and increasing the efficiency of intercropping cultivation.

In order to investigate the effect of weed infestation periods on Light absorption capacity and use efficiency by canopy of potato in seed producing and commercial plant density, an experiment was conducted in the farm of Agricultural faculty of Bu-Ali Sina University in 2006. The study was cal Tied out in a factorial experiment based on a randomized complete bloke design with three replications. The factors were potato plant density at two levels, 5.33 (optimum commercial density) and 6.66 (optimum seed producing density) plants per m-2 and weed infestation periods at seven levels, in which, weeds were allowed to grow for 10, 20, 30, 40 and 50 days after potato plant emergence and then weeds were removed manually until harvest. Two control including full- season weeded and full- season infested were taken. The amount of Light in the top and below the canopy was measured 10 days after potato plant emergence and repeated 8 times with 10 day intervals. Weeds were removed before Light measurement in each infestation period treatments. Weed and potato sampling was done at the Light measurement time to determine potato leaf area index and weeds total dry matter. The results showed that by increasing weed infestation periods, leaf area index, Light absorption and use efficiency, Light extinction coefficient and number of potato branches per area unit, decreased and weed total dry matter, increased. By increasing the infestation duration, potato tuber yield decreased significantly. The effects of weed infestation periods on the above trials in commercial plant density was more than that of seed producing plant density.

In order to evaluate Light extinction coefficient and Light use efficiency of wheat cultivars in densities of wild mustard, an experiment was conducted in Agricultural Research Station Gorgan during 2010-2012. The experiment design consisted of four randomized complete blocks in a factorial arrangement. The design consisted of two factors, four wheat cultivars and 5 levels of wild mustard densities. The results of means comparison of cultivar×wild mustard density interaction effect showed by increasing wild mustard density, Light extinction coefficient increased in wheat different cultivars. In this research, the means of Light extinction coefficient in the maximum of wild mustard density in Morvarid, Moghan, Arta and Tajan was 0.23, 0.51, 0.63 and 0.65, respectively. The highest and lowest of Light extinction coefficient observed in Tajan and Morvarid, respectively. By comparing the vertical distribution of leaf area in wheat cultivars was distinguished that the highest of gathering amount of leaf area in all of investigated layers observed in Morvarid in competition and pure conditions. The highest of Light use efficiency in the maximum of wild mustard density (32 plant/m2) observed in Morvarid (1.85 g/Mj) in the both of years, meanwhile, Tajan (1.21 g/Mj) had the lowest of Light use efficiency. Totally, the results of this experiment in two years showed Morvarid had the highest of seed yield for the reason that the most of vertical distribution of leaf area and Light use efficiency and too, the lowest of Light extinction coefficient in compared to other cultivars, and was the more of succeed in competition with wild mustard.

In order to study the effects of nitrogen and plant density on Light absorption and radiation use efficiency (RUE) in two spring rapeseed cultivars, a split plot factorial experiment based on randomized complete block design with four replications was conducted in 2005 in research farm of Ferdowsi University of Mashhad-Iran. The treatments included two levels of urea application (100 and 150 kg/ha) as main plots and subplots were combination of plant density (60, 80, and 100 plant/m2) and rapeseed cultivars (Hyola 308 and Option500, early and medium maturing cultivars, respectively). Results indicated that treatments influenced significantly on Light absorption rate and RUE. Increasing nitrogen application rate, from measured factors, only LAI and RUE were significantly influenced. Hyola 308 cultivar had higher RUE, biological and grain yield and oil yield compared to Option 500. The only preference of Option 500 cultivar was 1000 seed weight. Dry matter production and RUE was significantly higher in 80 plant/m2 compared to other plant densities. Increased dry matter in this density was due to higher Light absorption and consequently increased RUE. Among all determined parameters, LAI was significantly influenced, and highest LAI observed with Option 500 cultivar, which occurred in 100 plant/m2 density and 150 kg/ha urea application. Among yield components, only pod number per plant was affected by plant density, as highest number of pods observed in 60 plant/m2 treatment. None of the treatments influenced seed oil percentage.

Crop growth modeling for forecasting various plant's functions and their contribution to yield, is one of the ways to improve field management. This trial was set up to evaluate radiation use efficiency of mung bean, common bean and cowpea cultivars in a double cropping system. Field experiment was conducted at Research Farm of College of Agriculture, University of Tehran, Karaj. A 4-replicate group balanced block field experiment was set up. Results showed that the differences among three pulses were significant in terms of biomass (p<0.05). Cowpea, producing 5876.8 Kg/ha, had the highest yield among the species used in this study. Comparison of grain yield observed in this experiment with mono crop yield potential, showed that cowpea, common bean and mung bean produced 40%, 37% and 58% of their mono crop grain yield potential, respectively. In the late vegetative growth period, cowpea, mung bean and common bean absorbed 90%, 33% and 36% of photosynthetic active radiation, respectively. There was a significant difference among pulses, in terms of their radiation use efficiency and Light extinction coefficient (p<0.05 and p<0.01, respectively). Cowpea, common bean and mung bean had radiation use efficiencies of 0.84, 0.82 and 0.99, g/MJ and Light extinction coefficients of 0.605, 0.344 and 0.458, respectively. Results indicated that in some cultivars, when K decreases and LAI increases, LUE might be increased twice.

Differences in dry matter accumulation among crop cultivars can be attributed to differences in either the absorption of incident photosynthetic ally active radiation (PAR) and/or for the conversion of absorbed into dry matter. A field study was conducted in 1999 to quantify the effect of planting pattern on dry matter accumulation. The experiment was split plot design on randomized complete block basis with 3 replications. Main plots were allocated to planting patterns: rectangular, square and diamond, and the sub plots were consisted of three maize hybrids (KSC 704, KSC 301, KSC 108). The Results revealed that planting pattern had a significant effect an PAR and radiation use efficiency at different growth stages, especially after the beginning of the reproductive phase. Leaf area index and canopy Light extinction coefficient were significantly affected by planting pattern and cultivars. Significant differences were found among source of variations in respect of PAR absorbtion. Higher dry matter accumulation in square planting pattern was due to higher incident PAR and RUE compared to the other treatments.