Photo Selective Shade Net: An Effective Tool to Reduce the Impact of Global Warming and Pesticide Residues in Vegetable Production: A Review

Photo selective shade net is a product made of plastic fibers connected together with each other, forming a regular porous structure and allowing gases, liquid and light to pass through. It has a capacity to selectively filter the intercepted solar radiation, in addition to their protective function. Vegetables are considered as protective food which are highly perishable in nature. High temperature due to global warming, climate change and excessive use of chemicals are some of the burning issues of vegetable production. Photo selective shade net can be a partial solution for these problems. Vegetable crops grown under different photo selective shade net shows productive responses thus by application of various Photo selective shade nets we can improve the quality as well as production of vegetable crops.

The Effect of Diffuse Film Covers on Microclimate and Growth and Production of Tomato (Solanum lycopersicum L.) in a Mediterranean Greenhouse

The efficient use of light is one of the most important factors for the development of greenhouse crops. It is increasingly necessary to use film covers that enhance transmittance and the proportion of diffuse light to generate a more homogeneous light distribution. The objective of this study was to evaluate the effect that an experimental film cover with high transmittance and high light diffusivity produces on the microclimate and the growth and yield of tomato crops (Solanum lycopersicum L.), compared with a commercial thermal film cover. The trial was developed during a spring–summer growing cycle in a multispan greenhouse divided into two compartments (sectors) separated by a vertical polyethylene sheet. In the East sector, a commercial film was installed (transmittance of 85% and diffusivity of 60%) and in the West sector, an experimental film was used (transmittance of 90% and diffusivity of 55%). The results show an increase in the marketable yield of 0.25 kg·m−2 in the sector with the experimental film, which represents 3.2% growth with respect to the commercial film. The photosynthetic activity measured in tomato leaves was 21.5% higher in plants growing in the sector with the experimental film, with had the highest transmittance. The increase in radiation transmittance of 14% produced greater photosynthetic activity without generating a higher inside air temperature at the crop level (at the height of 2 m above the floor). However, the mean temperature of the soil surface was statistically higher on the side with the diffuse experimental cover film, as a logical consequence of the higher level of intercepted solar radiation.

Model Simulation of Soybean (Glycine Max (L.) Merrill) Growth by Energy Balance Approach

<p>Intercepted solar radiation by leaf will influence energy balance in plant. The energy balance in leaf is a complex process, which results in biomass growth. Here, we modeled leaf energy balance to estimate dry matter growth in soybean. In the field, we measured intercepted radiation in canopy (1 meter above surface) with two treatments: soybean with 50% shading (N50%M0) and no-shading (N0%M0) twice a week. Then we sampled a biomass with destructive technique every week in each treatment. Our results showed that the intercepted radiation in no-shading treatment was higher (400 J/m²) than those in shading one (250 J/m²). The results were consistence with the high biomass growth at 12 weeks after planting, which observed in no-shading treatment. Then we validated our model by 1:1 plot test. Our finding revealed that no-shading treatment showed a good agreement with the observed biomass (closed to 1:1 plot), whereas the shading treatment tended to predict under estimate of biomass.</p>

Dynamics of phytosterols content and concentration in sunflower grains

Phytosterols are allies in the control of plasma cholesterol and in preventing cardiovascular diseases. As vegetable oils are the main source of phytosterols, characterising environmental factors that determine phytosterols accumulation in the oil is an important objective. The present research focuses on evaluating how intercepted solar radiation (ISR, the main environmental factor affecting oil accumulation) can determine phytosterol accumulation in sunflower oil. The aim of this work was to study the dynamics of phytosterols accumulation under different ISR levels and its relationships with the dynamics of oil accumulation. Two field experiments were conducted with hybrids with different fatty acid composition. Treatments applied during grain filling were: two levels of defoliation (75% and 80%) and a control. A 50% grain thinning treatment was also applied. Oil phytosterols concentration increased with defoliation during grain-filling period, whereas phytosterols content per grain decreased. β-sitosterol and campesterol were the most affected sterols. Reduction in ISR did not affect the rates of phytosterols accumulation. The durations of the accumulation period of these components varied in accordance with the duration of oil accumulation period. These results reinforce the importance of environmental factor in determining oil quality in sunflower grains.

Dynamics of Intercepted Solar Radiation to Simulate Dry Matter of Soybean (Glycine Max (L.) Merrill)

<p>Solar radiation greatly affects the development of plant biomass. The process of plant development is complex. Here, we simplified this complexity through modeling experiment by integrating climate variables. This study aims to determine the dynamics of canopy intercepted solar radiation under soybean (<em>Glycine Max (L.) Merrill</em>). We employed the shierary-rice model to calculate plant biomass. The results showed that intercepted radiation continuosly increased during vegetative phase, whereas the radiation remains constant during generative phase. Our observation confirmed that the pattern of intercepted radiation followed the angular pattern of sunlight. The intercepted radiation was optimum at 10:00 to 14:00 pm, and it was used to form the plant dry matter. We found that the intercepted radiation contributed until 12%. Based on this contribution, we built our crop model of soybean biomass. Our model performed well in simulating dry biomass with high R² (0.9), and as indicated by the plot 1:1 between dry matter of model and field observations. Further, the result of t test between model and observed data confirm this strong corelation (<em>p-value</em> 0.07).</p>

Oil yield components and oil quality of high stearic-high oleic sunflower genotypes as affected by intercepted solar radiation during grain filling

High stearic-high oleic sunflower oil presents high thermal stability. This oil is an alternative to the hydrogenation process which produces trans fatty acids. The effect of intercepted solar radiation (ISR) per plant during grain filling on oil yield components and oil fatty acid composition was investigated in three sunflower high stearic-high oleic genotypes. Three field experiments were conducted and treatments to modify ISR per plant were applied during grain filling: shading, defoliating and thinning plants. Increasing ISR per plant linearly increased grain number per capitulum, weight per grain and in some cases palmitic and stearic acid percentages. In the hybrid, grain oil percentage and oleic acid concentration increased with a decreasing rate, reaching a maximum value at high levels of ISR per plant. Linoleic acid percentage decreased with a decreasing rate, reaching a minimum value at high levels of ISR per plant. Oil yield components presented heterosis. This information contributes to explain the effects of environment on yield and oil quality in high stearic-high oleic genotypes and could be used to design management practices that optimise these traits.

Cultivar effects on relationship between grain number and photothermal quotient or spike dry weight in wheat

SUMMARYIn wheat, the photothermal quotient (Q, the ratio between mean incident solar radiation and mean temperature is greater than 4·5°C in the 30 days preceding anthesis), is a good estimator of grain number/m2 (GN) and of yield. Previous investigations have not analysed in depth whether the responses of GN to Q differ between wheat cultivars, or what is the cause of the eventual variation. In the present work, the results of field experiments carried out between 1994 and 2001 in various locations were used to test the following hypotheses: (i) the responses of GN to Q differ between wheat cultivars; (ii) these differences are caused by differences in the spike fertility index (GN/g spike dry weight/m2 at the beginning of grain filling (SDW)). The responses of GN to Q were compared for five wheat cultivars (four bread wheats and one durum wheat) and it was found that with Q values above 0·3 MJ/m2/d°C, all responses of GN to Q were linear, positive and parallel. A method was then proposed to obtain cultivar-specific GN from a common relationship between GN and Q. This method would facilitate GN estimation in crops with changes in sowing dates, sites or years, starting from data of potential GN and yield that is relatively easy to obtain. Differences among cultivars in response to Q were due to differences in GN response at SDW. Similar SDW values produced different GN, depending on the spike fertility index of each cultivar. The cultivars did not differ in their responses of SDW to Q. The association between spike fertility index and SDW was strongly negative in bread wheat. At lower levels of Q or SDW, the spike fertility index increased in all cultivars, at least when changes in SDW or Q were caused mainly by intercepted solar radiation, but the present results demonstrate that differences between cultivars also exist in this relationship.

Relationship between oil tocopherol concentration and oil weight per grain in several crop species

The objectives of this work were (i) to analyse the effect of intercepted solar radiation (ISR) per plant during grain filling on oil tocopherol concentration in soybean, maize and rape and (ii) to investigate in these species if variations in oil tocopherol concentration are well accounted for by variations in oil weight per grain. Field experiments were conducted with genotypes of soybean, maize and rape. A genotype of sunflower was included as ‘control species’ as its behaviour was known from previous works. ISR was modified during grain filling by shading or thinning plants. Plants were harvested at physiological maturity and oil tocopherol concentration was determined by high performance liquid chromatography. Samples from other field or growth chamber experiments were also processed. In the four species, increasing radiation increased the oil and tocopherol weight per grain. Increasing ISR reduced oil tocopherol concentration in sunflower, soybean and rape but not in maize. The oil tocopherol concentration would be reduced by ISR in those species, with high oil contents in their grains, where the oil synthesis is more increased than tocopherol synthesis. The variations in oil tocopherol concentration were accounted for by variations in oil weight per grain only in those species with high and variable oil concentration.