One of the main purposes leading botanists to investigate the effects of ionizing radiations is to understand plant behaviour in space, where vegetal systems play an important role for nourishment, psychological support and functioning of life support systems. Ground-based experiments have been performed with particles of different charge and energy. Samples exposed to X- or γ-rays are often used as reference to derive the biological efficiency of different radiation qualities. Studies where biological samples are exposed directly to the space radiation environment have also been performed. The comparison of different studies has clarified how the effects observed after exposure are deeply influenced by several factors, some related to plant characteristics (e.g. species, cultivar, stage of development, tissue architecture and genome organization) and some related to radiation features (e.g. quality, dose, duration of exposure). In this review, we report main results from studies on the effect of ionizing radiations, including cosmic rays, on plants, focusing on genetic alterations, modifications of growth and reproduction and changes in biochemical pathways especially photosynthetic behaviour. Most of the data confirm what is known from animal studies: densely ionizing radiations are more efficient in inducing damages at several different levels, in comparison with sparsely ionizing radiation.

The presence of NaCl in soil or water is one of the\ud most critical environmental stresses limiting crop productivity\ud worldwide. Seaweed extract (SWE) represents an important\ud category of plant biostimulants able to improve crop tolerance\ud to abiotic stresses, such as salinity. The current research aimed\ud at elucidating the physiological and anatomical effects as well\ud as the changes in mineral composition of greenhouse zucchini\ud squash (Cucurbita pepo L.) treated with Ecklonia maxima\ud SWE. Plants were sprayed every 2 weeks with a solution\ud containing 3 mL L−1 of SWE. Zucchini squash plants were\ud supplied with four nutrient solutions: 1 (non-salt control), 20,\ud 40, or 60 mM NaCl. Increased salinity in the nutrient solution\ud triggered a decrease in marketable yield, shoot biomass, Soil\ud Plant Analysis Development (SPAD) index, net CO2 assimilation\ud rate (ACO2), transpiration rate (E), and leaf macronutrient\ud concentration (P, K, Ca, and Mg), whereas it augmented\ud Na and Cl concentrations in leaf tissue without altering PSII\ud photochemistry. Anatomical changes in leaves, including an\ud increase in lamina, palisade, spongy parenchyma thickness,\ud and intercellular spaces, were recorded under saline conditions.\ud Foliar application of SWE increased yield and shoot\ud biomass by 12.0 and 17.4 %, respectively, as well as fruit\ud dry matter and total soluble solid contents in comparison to\ud untreated plants. This was associated with an improvement in\ud ACO2 (+14 %), chlorophyll content (+8 %), and nutritional\ud status (high K and low Na accumulation) in SWE-treated\ud plants. The size of stomata was influenced by foliar application\ud of SWE, since the smallest cell guard length and width\ud were recorded in the leaves ofSWE-treated plants. Finally, the\ud phenolic compounds in both palisade and spongy parenchyma\ud were higher in untreated than in SWE-treated plants

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Abiotic stresses can cause a substantial decline in fruit quality due to negative impacts on plant growth, physiology and reproduction. The objective of this study was to verify if the use of a biostimulant based on plant and yeast extracts, rich in amino acids and that contains microelements (boron, zinc and manganese) can ensure good crop yield and quality in tomato plants grown at elevated temperatures (up to 42 °C). We investigated physiological responses of four different tomato landraces that were cultivated under plastic tunnel and treated with the biostimulant CycoFlow. The application of the biostimulant stimulated growth (plants up to 48.5% taller) and number of fruits (up to 105.3%). In plants treated with the biostimulant, antioxidants contents were higher compared to non-treated plants, both in leaves and in fruits. In particular, the content of ascorbic acid increased after treatments with CycoFlow. For almost all the traits studied, the effect of the biostimulant depended on the genotype it was applied on. Altogether, the use of the biostimulant on tomato plants led to better plant performances at elevated temperatures, that could be attributed also to a stronger antioxidant defence system, and to a better fruit nutritional quality.

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