Does Regulated Deficit Irrigation Affect Pear Fruit Texture by Modifying the Stone Cells?

Regulated deficit irrigation (RDI) strategies aim to improve water usage without reducing yield. Generally, irrigation strategy effectiveness is measured as fruit yield, with little consideration of fruit quality. As water deficit and increased plant cell sclerification are often associated, this study explored the effect of RDI on pear fruit stone cells, a crucial trait affecting flesh texture. The presence, distribution, and development of pear fruit stone cells under RDI and full irrigation were compared using Pyrus communis L. cv. Barlett trees, employing recently developed microscope image analysis technology. The control treatment was maintained under non-stress conditions, while the RDI treatment received an average of 15% of the control water during the latter part of Stage I fruit development. Observations at the end of Stage I and at harvest revealed no effect on stone cell presence under the RDI strategy tested. The relative area of stone cells within the flesh was greater at Stage I than at harvest, as stone cell expansion occurred early in development, while the (unsclerified) parenchyma cells, a dominant component of the fruit flesh, expanded until harvest. Stone cell cluster density was higher near the fruit core than in the cortex center and exterior. These initial results suggest that well-planned RDI strategies will generally not affect pear fruit stone cell content and, thus, textural quality. Microscope image analysis supported the results from previously used analytical techniques, mainly chemical, while providing a tool for better understanding the process and factors involved in the timing of stone cell differentiation.

Characterization of the biochemical basis for copper homeostasis and tolerance in Biscutella auriculata L.

Biscutella auriculata L. is a plant that belongs to the Brassicaceae family and it has been found growing in a metal-contaminated area of the San Quíntín mine (Ciudad Real, Spain). The purpose of this work was to evaluate the mechanisms that allow this plant to tolerate high concentrations of copper. Seedlings were grown in a semi-hydroponic system for 15 days under 125 µM of Cu (NO3 )2 . Exposure to copper resulted in growth inhibition and reduction in the photosynthetic parameters. Copper was mainly accumulated in vascular tissue and vacuoles of the roots and only a minor proportion was transferred to the shoot. Biothiol analysis showed a greater enhancement of reduced glutathione in leaves and increases of phytochelatins (PC2 and PC3) in both leaves and roots. Copper treatment induced oxidative stress, which triggered a response of the enzymatic and non-enzymatic antioxidant mechanisms. The results show that B. auriculata is able to tolerate high metal levels through the activation of specific mechanisms to neutralize the oxidative stress produced and also by metal sequestration through phytochelatins. The preferential accumulation of copper in roots provides clues for further studies on the use of this plant for phytostabilization and environmental recovery purposes in Cu-contaminated areas.

Antigerminative comparison between naturally occurring naphthoquinones and commercial pesticides. Soil dehydrogenase activity used as bioindicator to test soil toxicity.

As important secondary plant metabolites, naphthoquinones exhibit a wide range of biological activities, and one of their roles in the competition among plants is a well-known process called allelopathy. Their potential as a sustainable alternatives to herbicides has been investigated. In this study, we aim to take advantage of these naturally occurring substances to control the germination of spontaneous flora. In this work, the sensitivity of the germination of different plant species (horticultural, grasses and spontaneous flora) was tested. The results indicate that most of the plants are sensitive to juglone. The comparison between naphthoquinones and commercial pesticides did not provide enough evidence to use naphthoquinones to control spontaneous flora. Assessing the toxicity of pesticides is crucial because the sustainability of the ecosystem could be endangered by their use. In this study, the toxicity of certain pesticides (metam Na, oxyfluorfen, glyphosate, metribuzin and diuron) was evaluated based on dehydrogenase activity (DHA). DHA has become a good bioindicator for assessing the toxicity of xenobiotics. A toxicity index was proposed to compare the different degrees of toxicity among the tested substances. Finally, a toxicity threshold was constructed using the slopes of the fitted lines of the data, assuming that the maximum toxicity (10) represented the slope of the biocide HgCl2 and that the minimum toxicity (1) was attributed to the DHA obtained from soil without pesticides.