a b s t r a c tIn recent years, the interest toward the applicability of Light-Emitting Diode (LED) lights for indoor cultivation has significantly grown. The present work addressed the physiological and phytochemical plant responses to LED lights in indoor cultivation of leafy and fruit vegetable crops (namely sweet basil, Ocimum basilicum L.; and strawberry, Fragaria × Ananassa), with the final aim of improving both productivity and nutritional quality. Artificial light treatments were applied in a multi-sectorial growth chamber equipped with lamps with different light incidence and spectra (with red:blue ratio ranging 0.7-5.5). In all experiments, increased plant biomass, fruit yield and energy use efficiency (EUE) were associated to LED treatments, confirming the superiority of LED compared to the traditional fluorescent lamps. Interestingly, LED lighting enabled to increase antioxidant compounds and reduce nitrates content in basil leaves. A spectral red:blue ratio of 0.7 was necessary for proper plant development and improved nutraceutical properties in both crops.

Fresh water resources are limited and their use in agricultural production is expected to come under increasing constraints. Eighteen Syrian lines of potato (Solanum tuberosum L.) were screened for drought tolerance by measuring aerial and root growth in vitro. Drought stress was evaluated by adding 2, 4, 6, 8 and 10 % (w:v) of sorbitol to MurashigeSkoog medium and compared to 0 % for the control. Water potential of media ranged from −0.58 MPa to −2.5 MPa. Water-stress in culture adversely affected plant growth, and genotypes differed for their responses. Plant length and stem thickness, leaf area, root number length and thickness, and plant fresh and dry weights and plant water content were measured and all decreased due to drought. Grouping lines by cluster analysis for response to drought resulted in: (1) a tolerant group of six lines, (2) a moderately tolerant group of seven lines, and (3) a susceptible group of five lines. The variation in germplasm indicated that potato varieties can be developed for production under some levels of drought.

Water availability is considered as a determinant factor that affects plant growth. The commercial medicinal values of an aromatic plant rely on the presence of secondary metabolites that are affected under water shortage. Two-year-oldThymus citriodorusplants were subjected to different polyethylene glycol (PEG-6000) levels (0, 2%, and 4%) under greenhouse condition. PEG treatment lasted for 15 days. Thyme plant showed a morphological drought avoidance mechanism by maintaining the root system development through shoot fresh weight reduction resulting in promoted root absorption capacity and sustained plant growth. Moreover, stressed plants were able to maintain water use efficiency and root : shoot ratio suggesting a strong relation between root water uptake and water use saving strategies. Furthermore, thyme plants reduced tissue dehydration through stomatal closure and improved root water uptake. Content of volatile oil constituents of geraniol and diisobutyl phthalate increased upon drought stress while pseudophytol was reduced. Unexpectedly, thymol was not reported as a main oil element under either control or mild stress condition, while it was increased upon high drought stress in measure of 4.4%. Finally, carvacrol significantly accumulated under high drought stress (+31.7%) as compared to control plants.

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Grafted plants are often more tolerant to salinity than nongrafted controls. In order to distinguish differential response components in grafted melon (Cucumis melo L.), salt stress was imposed on several rootstock–scion combinations in four experiments. The rootstock used was an interspecific squash (Cucurbita maxima Duch. × Cucurbita moschate Duch.), RS841, combined with two cantaloupe (C. melo var. cantalupensis) cultivars, namely London and Brennus, against both self-grafted and nongrafted controls. Physiological, morphological and biochemical adaptations to 0, 40 and 80 mM NaCl were monitored. Upon salinity, plant biomass and leaf area were improved by grafting per se, since self-grafted plants performed similarly to the heterografted ones. However, improvements in the exclusion of Na+ and the uptake of K+ were due only to the rootstock genotype, since ionic composition was similar in self-grafted and nongrafted plants. These results indicate that the favourable effects of grafting on plant growth cannot be ascribed to a more efficient exclusion of Na+ or enhanced nutrient uptake. On the other hand, growth improvements in both self- and heterografted plants were associated with a more efficient control of stomatal functions (changes in stomatal index and water relations), which may indicate that the grafting incision may alter hormonal signalling between roots and shoots.