ARI REVIEW FOR 2016-2017

Spatial and temporal variations of evapotranspiration and net water requirements of typical Mediterranean crops on the island of Cyprus Diminishing irrigation water availability and increased crop evapotranspiration (ET) have already been shown to pose threats to agricultural productivity. The Section of Natural Recourses and Environment of ARI performed a study aiming to estimate the values and trends of both ET and net irrigation requirements (NIR) of those crops consuming most water due to the size of their cultivated area (citrus and potatoes) in a water-scarce region with typical Mediterranean climate, such as Cyprus, analyse possible spatial and temporal variations of these parameters, and discuss implications of this analysis on agricultural water conservation. A linear regression analysis of ET and NIR values of potatoes and citrus during recent decades in their four main cultivated areas revealed both increasing and decreasing trends for these parameters. Overall, however, the results did not show any change in irrigation water demands for these crops during recent years. In accordance with this outcome, average ET and NIR values of the majority of cultivated crops on the island showed no statistically significant differences between the periods 1976–2000 and 1990–2014. Conversely, this was not the case when data were analysed within each weather station across crops. It is suggested, therefore, that agricultural water resource management schemes should not be focused merely on a regional analysis of changes but that emphasis should be given to site-specific values and trends of ET and NIR estimations, ultimately serving the conservation of agricultural water. ( A. Christou, P. Dalias, D. Neocleous ) Melatonin systemically ameliorates drought stress-induced damage in Medicago sativa plants by modulating nitro-oxidative homeostasis and proline metabolism Recent reports have uncovered the multifunctional role of melatonin in plant physiological responses under optimal and suboptimal environmental conditions. We explored whether melatonin pretreatment could provoke priming effects in alfalfa ( Medicago sativa L.) plants subsequently exposed to prolonged drought stress (7 days), by withholding watering. Results revealed that the rhizospheric application of melatonin (10 μmol L −1 ) remarkably enhanced the drought tolerance of alfalfa plants, as evidenced by the observed plant tolerant phenotype, as well as by the higher levels of chlorophyll fluorescence and stomatal conductance, compared with non-treated drought-stressed plants. In addition, lower levels of lipid peroxidation (MDA content) as well as of both H 2 O 2 and NO contents in primed compared with non-primed stressed plants suggest that melatonin pretreatment resulted in the systemic mitigation of drought-induced nitro-oxidative stress. Nitro-oxidative homeostasis was achieved by melatonin through the regulation of reactive oxygen (SOD, GR, CAT, APX) and nitrogen species (NR, NADHde) metabolic enzymes at the enzymatic and/or transcript level. Moreover, melatonin pretreatment resulted in the limitation of cellular redox disruption through the regulation of the mRNA levels of antioxidant and redox-related components ( ADH, AOX, GST7, GST17 ), as well via osmoprotection through the regulation of proline homeostasis, at both the enzymatic (P5CS) and gene expression level ( P5CS, P5CR ). Overall, novel results highlight the importance of melatonin as a promising priming agent for the enhancement of plant tolerance to drought conditions through the regulation of nitro-oxidative and osmoprotective homeostasis. ( A. Christou ) SOIL FERTILITY IMPROVEMENT Research on fertilisation using organic amendments has been focused on the use of animal manures aiming to provide tools for balancing plant requirements and inputs. The characterisation of hydrochar and the study of the constraints for its use in growing media have also been initiated. 56 Natural Resources and Environment