Growth and Physiological Characteristics of Strawberry Plants Cultivated under Greenhouse-Integrated Semi-Transparent Photovoltaics.

The integration of semi-transparent photovoltaics into the roof of greenhouses is an emerging technique used in recent years, due to the simultaneous energy and food production from the same piece of land. Although shading in many cases is a solution to maintain the desired microclimate, in the case of photovoltaic installations, the permanent shading of the crop is a challenge, due to the importance of light to the growth, morphogenesis, and other critical physiological processes. In this study, the effect of shade from semi-transparent photovoltaics on a strawberry crop (Fragaria x ananassa Duch.) was examined, in terms of growth and quality (phenolic and flavonoid concentration of fruits). According to the results, in non-shaded plants, there was a trend of larger plants, but without a significant change in leaf number, while the total number of flowers was slightly higher at the end of the cultivation period. Moreover, it was found that the percentage change between the number of ripe fruits was smaller than that of the corresponding change in fruit weight, implying the increased size of the fruits in non-shaded plants. Finally, regarding the antioxidant capacity, it was clearly demonstrated that shading increased the total phenolic content, as well as the free-radical-scavenging activity of the harvested fruits. Although the shading from the semi-transparent photovoltaics did not assist the production of large fruits, it did not affect their number and increased some of their quality characteristics. In addition, the advantageous impact of the semi-transparent photovoltaics in the energy part must not be neglected.

Seasonal Differences in Leaf Photoprotective Potential between Adults and Juveniles of Two Mediterranean Perennials with Distinct Growth Forms: A Comparative Field Study.

The photosynthetic differences between adult and juvenile Mediterranean plants were previously studied under field conditions, yet the corresponding differentiation of their photoprotective efficiency has not been sufficiently investigated. The present study aims to examine possible differences in the photoprotective potential between adults and juveniles of two native Mediterranean plants with distinct growth forms. Thus, the seasonal variations in individual carotenoids, electron transport rate (ETR), and non-photochemical quenching (NPQ) were monitored in fully exposed mature leaves from adults and juveniles of the winter deciduous tree Cercis siliquastrum L. and the evergreen sclerophyllous shrub Nerium oleander L. All plants were grown under apparently similar field conditions. In both species, juveniles displayed substantially lower ETR and increased NPQ values than adults in spring, with the differences intensifying during summer drought and diminishing in autumn. Concomitantly, juveniles showed significantly higher chlorophyll-based total carotenoids in spring and summer mainly due to the higher investment in xanthophyll cycle components (VAZ), in combination with an increased mid-day de-epoxidation state (DEPS) and partial retention of zeaxanthin in the dark. In N. oleander, although ETR was lower in juveniles during winter, NPQ was extremely low in both ages. In conclusion, juveniles exhibit enhanced photoprotection potential, especially in the summer, due to their reduced photochemical capacity. The photosynthetic superiority of adults during the favorable spring period may be attributed to the needs of the co-existing reproductive effort.

Integration of biophysical photosynthetic parameters into one photochemical index for early detection of Tobacco Mosaic Virus infection in pepper plants.

Photosynthesis in host plants is significantly reduced by many virus families. The early detection of viral infection before the onset of visual symptoms in both directly and systemically infected leaves is critical in crop protection. Viral pathogens cause a variety of symptoms through modifications of chloroplast structure and function and the response of the photochemistry process is immediate. Therefore, chlorophyll fluorescence monitoring has been extensively investigated the last two decades as a tool for timely assessment of pathogenic threats. Alternatively, the analysis of Chla fluorescence transients offers several interlinked parameters which describe the fate of excitation energy round and through the photosystems. Additionally, OJIP fluorescence transients and leaf reflectance spectra methodologies serve for rapid screening of large number of samples. The objective of the present study was to achieve early detection of viral infection, integrating the multiparametric information of the Chla fluorescence transients and of the leaf reflectance spectra into one photochemical performance index. Infection decreased the maximum quantum yield of PSII (FV/FM), the effective quantum yield of PSII (ΦPSII), the CO2 assimilation rate (A) and the stomatal conductance (gs) in the studied TMV-pepper plant pathosystem, while non-photochemical quenching (NPQ) increased. Some parameters from the OJIP transients and the leaf reflectance spectra were significantly affected 24 h after infection, while others modified three to five days later. Similar results were obtained from systemically infected leaves but with one to three days hysteresis compared to inoculated leaves. Differences between healthy and infected leaves were marginal during the first 24 h post infection. The Integrated Biomarker Response tool was used to create a photochemical infection index (PINFI) which integrates the partial effects of infection on each fluorescence and reflectance index. The PINFI, which to the best of our knowledge is the first photochemical infection index created by the IBR method, discriminated reliably between the infected and healthy leaves of pepper plants from the first 24 h after infection with the TMV.

Conservation of Micromeria browiczii (Lamiaceae), Endemic to Zakynthos Island (Ionian Islands, Greece).

The massive decline in biodiversity due to anthropogenic threats has led to the emergence of conservation as one of the central goals in modern biology. Conservation strategies are urgently needed for addressing the ongoing loss of plant diversity. The Mediterranean basin, and especially the Mediterranean islands, host numerous rare and threatened plants in need of urgent conservation actions. In this study, we assess the current conservation status of Micromeria browiczii, a local endemic to Zakynthos Island (Ionian Islands, Greece), and estimate its future risk of extinction by compiling and assessing scientific information on geographical distribution, population dynamics and reproductive biology. The population size and the geographical distribution of the species were monitored for five years. The current population of the species consists of 15 subpopulations. Considerable annual fluctuation of population size was detected. The species is assessed as Endangered according to the International Union for Conservation of Nature threat categories. According to population viability analysis results, its extinction risk was estimated to be 5.6% over the next 50 years, when six of the fifteen subpopulations (40%) might become extinct. The investigation of certain aspects of the species' biology yielded important data necessary to identify critical aspects for its survival and to propose conservation measures.

Effect of organic carbon and nutrient supplementation on the digestate-grown microalga, Parachlorella kessleri.

Digested effluents are usually deprived of the appropriate levels of organic carbon or macro- and micro-nutrients to effectively sustain microalgal growth. In this regard, Parachlorella kessleri was cultivated in an agro-waste digestate supplemented with different glucose concentrations, magnesium and trace metals and alternatively with cheese whey (CW), with view to enriching digestate with organic and inorganic constituents and decreasing freshwater demand. Between the conditions tested, CW addition resulted in the highest biomass concentration, 2.68 g L-1 within 18 days of cultivation. Chlorophyll content significantly decreased under 5 g L-1 glucose addition, in contrast to MgSO4 co-addition and CW supplementation. The latter also induced high photosynthetic activity and better-preserved vitality of the photosynthetic apparatus, compared to sole glucose addition. Concerning lipid accumulation, in the presence of high glucose concentration, % of total fatty acids decreased, and the saturated fraction increased over polyunsaturated fatty acids (PUFAs).

Selection of microalgae intended for valorization of digestate from agro-waste mixtures.

Digestates have been recently recognized as valuable substrates for microalgal cultivation, effectively combining wastewater remediation and biofuels production. In this regard, selection of the appropriate species for such a process is of utmost importance. In this study, the performance of seven different microalgal strains in 10% (v/v) digestate which derived from the co-digestion of several agro-waste streams was investigated. Parachlorella kessleri, Acutodesmus obliquus, Chlorella vulgaris and Tetraselmis tetrathele were able to acclimate to this new medium, resulting in biomass yields and fatty acids (FAs) content which varied between 570-1117 mg L-1 and 3.9-24.5%, respectively. The main FAs detected in the four species were oleic, palmitic and linolenic acid, with significant differences in their relative abundance. Concerning nutrients removal, almost complete NH3-N removal was observed, while % TP removal exceeded 80% for three of the four strains tested. Furthermore, induction kinetics of prompt chlorophyll fluorescence was used as a screening tool indicative of the reactions of the photosynthetic machinery of different microalgal species cultivated in digestate.

Microalgal post-treatment of anaerobically digested agro-industrial wastes for nutrient removal and lipids production.

The aim of this study was to investigate the effectiveness of cultivating Parachlorella kessleri and Acutodesmus obliquus, in anaerobic digestion effluent (ADE) derived from the co-digestion of end-of-life dairy products with mixtures of agro-industrial wastes. To this end, their performance under sterile and non-sterile conditions and different ADE loadings was evaluated, in terms of biomass and lipid production, nutrient removal efficiency and vitality of the photosynthetic apparatus. 10% (v/v) ADE loading inhibited growth over 9-12days of cultivation, however biomass yields of 1.1 and 1gL-1, 22.7% and 19.5% (w/w) fatty acids concentration, as well as NH3-N assimilation of 49.7mgL-1 and 32.3mgL-1 and TP removal of 84.2% and 84% were recorded for P. kessleri and A. obliquus, respectively. Among all the ADE-based treatments tested, P. kessleri outperformed A. obliquus, with no differences observed between sterilized and non-sterilized ADE.

Photosynthesis in developing leaf of juveniles and adults of three Mediterranean species with different growth forms.

Leaf development is influenced by almost all the prevailing environmental conditions as well as from the conditions at the time of bud formation. Furthermore, the growth form of a plant determines the leaf longevity and subsequently the investment in biomass and the internal structure of the mesophyll. Therefore, photosynthetic traits of a growing leaf, though, partly predetermined, should also acclimate to temporal changes during developmental period. In addition, the age of the plant can affect photosynthesis of the growing leaf, yet, in the majority of studies, the age is associated to the size of the plant. To test if the reproductive status of the plant affects the time kinetics of the photosynthetic capacity of a growing leaf and the relative contribution of the plants' growth form to the whole procedure, field measurements were conducted in juveniles (prereproductive individuals) and adults (fully reproductive individuals) of an evergreen sclerophyllous shrub (Nerium oleander), a semi-deciduous dimorphic shrub (Phlomis fruticosa), and a winter deciduous tree with pre-leafing flowering (Cercis siliquastrum). PSII structural and functional integrity was progressively developed in all species, but already completed, only some days after leaf expansion in P. fruticosa. Developing leaf as well as fully developed leaf in adults of C. siliquastrum showed enhanced relative size of the pool of final PSI electron acceptors. Photosynthetic traits between juveniles and adults of P. fruticosa were similar, though the matured leaf of adults exhibited lower transpiration rates and improved water-use efficiency than that of juveniles. Adults of the evergreen shrub attained higher CO2 assimilation rate than juveniles in matured leaf which can be attributed to higher electron flow devoted to carboxylation, and lower photorespiration rate. The reproductive phase of the plant seemed to be involved in modifications of the PSII and PSI functions of the deciduous tree, in carboxylation and photorespiration traits of the evergreen shrub, and in water conductance efficiency of the semi-deciduous shrub. However, it is interesting, that regardless of the growth form of the plant and the prospective leaf longevity of the developing leaf, adults need to support flowering outmatch juveniles, in terms of photosynthesis.