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Increase of frequency, duration, and intensity of drought and heatwave and related water and heat crops stress are among the principal effects of climate change. This paper reports: (i) the effect of calcite particle film (CaPF) as a mitigation strategy against heat stress in well-watered (WW) or in drought-stress (D) conditions; and (ii) response of leaf angle variation to stomatal conductance changes induced by drought stress of Aleatico grapevine cultivar. Results have showed that CaPF, under WW conditions, reduced leaf temperature, and increased gas exchange, but, under very severe water stress, CaPF treatment was ineffective. Leaf angle ranged from 70° (WW vines) to 100° (drought stressed vines) and showed a good fit (R2 =0.81) with stomatal conductance within the range of 0.25 – 0.05 mol m-2 s–1 proving it might be a reliable proxy of vine water status.

Application of processed particles is widely developed to reduce abiotic stress damage and improve water use efficiency in perennial fruit crops. Our study determined the effect of processed calcite particles (Megagreen®) on water relations and photosynthesis in potted vine of ‘Cot’ grape cultivar (Vitis vinifera L.) grown in a glasshouse. Well-watered and drought stressed vines were either unsprayed or sprayed with Megagreen at different doses (0.00, 0.33, 0.66, 1.00 and 1.33 % w/v). Water stress affected predawn and midday leaf water potential, maximal CO2 assimilation (Amax), stomatal conductance (gs) and photosystem II efficiency (ФPSII) of the younger fully expanded leaves. Megagreen was able to restore Amax and ФPSII in water stressed plants. This effect was associated with a positive but less pronounced effect on gs and leaf transpiration. The beneficial effects of Megagreen were also observed on young and old leaves, at low and high atmospheric vapor pressure deficit and, in the morning as well as the afternoon. In water stress plants, Amax was strongly improved by increasing air CO2 concentration. Under these conditions, Megagreen did not increase CO2 fixation. Thus, it is suggested that Megagreen prevailing mechanism of action is an increase in stomatal conductance of grapevines subjected to drought conditions.

Foliar fertilization in rain-fed olive orchards is used nowadays in order to improve the yields for the olive oil industry. The present work aimed to study the effect of foliar fertilization on the quality parameters of olive fruits. Three foliar fertilizers and biostimulants were applied on Chemlali olive cultivar, cultivated under rain-fed conditions in the center of Tunisia, at different stages from the vegetative cycle during two successive years. Six treatments formed the fertilization program: F1 (rich in nitrogen), F2 (rich in boron), F4 (a biostimulant rich in calcium), F3 (supplying an addition of F1 and F2), F5 (supplying an addition of F1, F2 and F4) and a control (without foliar fertilization). At the end of the experiment during the year 2015, fruits were harvested, freeze-dried and the characteristics of drupes and chemical composition of the fruits were evaluated: mineral composition, carbohydrates profile and individual polyphenols. Results showed that some treatments especially rich in Ca improved the fruit size. Foliar fertilization induced differences in the mineral content of fruits. Regarding carbohydrates, glucose was the main sugar present in the fruits and varied between 8.8 μg/mg dry weight (d.w) and 36.43 μg/mg (d.w.). Changes were clearly observed in the pool of the phenolic fraction. The combined treatment F5 showed the highest concentrations in oleuropein and hydroxytyrosol and were equal to 742.6 and 112.94 μg/g of fresh weight respectively. This work is of great interest because it showed the role of nutrients supply in improving the quality of olive fruits. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2006.11.010 Byline: Beligh Mechri (a)(b), Faouzi Attia (b), Mohamed Braham (b), Salem Ben Elhadj (c), Mohamed Hammami (a) Keywords: Olive mill wastewaters; Phosphate rock; Extractable P olive tree; Agronomic application Abstract: Olive mill wastewater (OMW), a by-product of the olive-mill industry, is produced in large amounts in Mediterranean countries. The presence of indigenous phosphate deposits in some countries like Tunisia provides an incentive for direct application or local chemical treatment at low cost to improve the solubility of low reactive phosphate rocks (PRs). The use of naturally occurring low-molecular weight organic acids (LMWOAs) that are present in OMW represents a new perspective in PR research and a possible solution for the recycling of the OMW. The present work was aimed at evaluating, under natural situations (field of olive trees), the effects of agronomic application of OMW (amounts applied: 30, 60m.sup.3 ha.sup.-1) with PR (amounts applied: 150kgha.sup.-1) on olive trees soil properties. We measured organic C, nitrogen (N), extractable phosphorus (P), exchangeable calcium (Ca), and exchangeable potassium (K), as well as other properties (pH and electrical conductivity). Our data provide evidence that agronomic application of OMW with PR has important effects on soil properties. Increases in organic C, total N, extractable P and exchangeable potassium (K) were found after the first agronomic application of OMW and PR. These increases were only temporary, following the second agronomic application of OMW and PR, significant reductions were detected in the extractable soil P (19.67mgkg.sup.-1 in the control soil vs. 8.99mgkg.sup.-1 in the amended soil). Changes in the extractable soil P could alter plant productivity and plant community structure because shifts in nutriment availability can affect the balance between limiting and non-limiting nutrients. Author Affiliation: (a) Laboratoire de Biochimie, USCR Spectrometrie de Masse, UR Nutrition et Desordres Metaboliques, Faculte de Medecine, Monastir, Tunisie (b) Laboratoire d'Ecophysiologie, Institut de L'Olivier, Station de Sousse, Tunisie (c) Institut Nationale Agronomique de Tunisie, Tunisie Article History: Received 12 March 2006; Revised 19 October 2006; Accepted 11 November 2006

Growth and biochemical parameters of leaves, flower buds and flowers of olive (Olea europaea L. cv. Chemlali) treated by foliar biofertilization (T0: untreated trees; T1: rich in nitrogen (N), phosphorus (P), potassium (K); T2: rich in calcium (Ca); T3: application of T1 and T2) were analyzed during the flowering stage. The results showed that T1 resulted in higher contents of leaf N, K, and Na. T1 and T3 resulted in an increase of pigment concentration in leaves. All foliar treatments affected negatively the contents of total polyphenols and orthodiphenols in leaves and flower buds. Lower amounts of individual phenolic compounds were detected in the leaves under all foliar bio-fertilizations and in flower buds of olive trees sprayed with T2 and T3. This decrease is explained by the lower enzymatic activity of L-phenylalanine ammonia-lyase. In flowers, T1 exhibits the highest levels of total polyphenols, o-diphenols, and individual phenolic compounds compared to T0. [ABSTRACT FROM AUTHOR]