Mesh Crop Cover Optimizes the Microenvironment in a Tropical Region and Modifies the Physiology and Metabolome in Tomato

In tropical regions, high light levels can lead to increased photooxidative damage in plants. Thus, reducing solar radiation could have a substantial impact on crop performance. This study aimed to evaluate the physiological responses and metabolic profile of two tomato varieties grown in microenvironments modified with cover meshes under a high light level and a warm climate. The experiment was achieved under high solar irradiance and an unfavorably high temperature. The varieties "Moneymaker" (MM) and "Campeche 40" (C40) were grown from 45 to 130 days after sowing at four solar irradiance levels: 100% (T1), 80% (T2), 75% (T3), and 50% (T4). In both varieties, the plants grown under the lowest irradiances (T3 and T4) were the tallest, with larger leaf areas, and accumulated more aerial and root biomass. Under moderate shading (T2), plants took better advantage of the light and had the highest photochemical quenching coefficient (qP) (C40 = 0.60 and MM = 0.48) and the highest electron transport rate (ETR). However, T3 and T4 plants had the highest net assimilation rate (23.6 and 23.9 & mu;mol m(-2) s(-1) in C40, and 22.7 and 22.6 & mu;mol m(-2) s(-1) in MM, respectively) and the highest A/Ci coefficients. Although both tomato varieties accumulate similar metabolites, MM leaves accumulate more glucose and C40 leaves accumulate more proline and valine. Furthermore, MM leaves accumulate more glycine and GABA under high radiation, and C40 leaves accumulate more proline and valine than leaves under 50% shade (T4). We conclude that using meshes in areas with high irradiance could be an alternative to reduce abiotic stress factors in plants.