ABSTRACT
Melon is among the most consumed fruits in the world, being a crop that depends almost entirely on insects for its reproduction, which is why it is especially sensitive to declining pollination services. Restoration and maintenance of hedgerows and agricultural borders around crops are generally carried out by sowing flowering herbaceous plants or establishing shrubby species; however, a cost-effective and lower-maintenance alternative for farmers could be as simple as allowing vegetation to regenerate naturally without any management actions. This work aimed to test the effects of three different types of margins (managed herbaceous, managed shrubby, and unmanaged herbaceous) on the overall abundance and richness of wild pollinators in melon crops. The work was performed in three localities in southern Spain over two years. Pollinators were monitored visually using 1 × 1 m sampling squares and pan traps within melon fields. Moreover, crop yield was estimated by measuring fruit weight and the number of seeds. In general, higher abundances of pollinators were observed in melon fields during the second year. In addition, the abundances of Syrphidae, Andrenidae, Apidae (excl. Apis mellifera), and pollinators other than bees, belonging to the orders Diptera, Coleoptera, Hymenoptera, and Lepidoptera, showed higher values in melon fields with shrubby margins than in fields with herbaceous margins (managed or unmanaged). However, no effect of floral margins on the yield of melon crops was found.
ABSTRACT
Sun (Chrysanthemum morifolium) and shade (Spathiphyllum wallisii) plants were used to study the effects of drought, heat and high illumination. The stress conditions caused a greater accumulation of hydrogen peroxide in Chrysanthemum morifolium than in Spathiphyllum wallisii leaves. They also resulted in down-regulation of linear electron transport in the leaves of both species, as indicated by a gradual reduction in the photochemistry efficiency of PS II, which was associated with an increase in the non-photochemical quenching of fluorescence. Only a slight decrease in F(v)/F(m) was observed under stress conditions in either plant species, suggesting that the chloroplast is protected by mechanisms that dissipate excess excitation energy to prevent damage to the photosynthetic apparatus. In addition to the effects on photosynthetic activity, changes were also observed by immunoblot analysis in the plastidial NADH DH complex, PTOX and PGR5. The quantities of the PTOX and NDH-H subunit of the thylakoidal NADH DH complex, and the NADH DH activity in the thylakoid membranes were similar in control plants of both species and increased in stressed plants, particularly in Spathiphyllum wallisii. The level of PGR5 polypeptide was higher in Chrysanthemum morifolium than in Spathiphyllum wallisii control plants, while after stress, the quantity of PGR5 increased significantly in Chrysanthemum morifolium and remained constant in Spathiphyllum wallisii. These results indicate that the relative importance of chlororespiration and the cyclic electron pathways in the tolerance to drought, heat and high illumination differs in sun and shade plants, indicating different adaptive mechanisms to the environment. In the conditions studied, the PGR5-dependent cyclic pathway is more active in Chrysanthemum morifolium, a sun species, whereas in Spathiphyllum wallisii, a shade species, other ways involving the NADH DH complex and PTOX are stimulated in response to stress, which results in lower levels of ROS accumulation in the leaves.
