Field performance of seedlings and microproppagated plants of carob tree

Micropropagated plantlets of cv. Mulata and cv. Galhosa growing in pots, after acclimatization in the glasshouse and growth for several months under natural conditions, were transferred to a field trial. Carob seedlings of ‘Mulata’ were also transferred under the same conditions. The field trial has been established with 100% of success in micropropagated plants and 97% in seedlings. Three months after transfer to the field, plants showed good growth but micropropagated plants of ‘Mulata’ exhibited more vigour than ‘Galhosa’ and than seedlings, with the greatest number of branches and a larger length increase in the main stem. Before transference to the field, net photosynthetic rates (PN), water use efficiency (PN/gs) and quantum yield of PSII (fPSII) of the potted plants were higher in seedlings than in micropropagated plants. Three months after transplantation all gas exchange parameters were improved for all types of plants, particularly net photosynthetic rate, and no significant differences were observed between plants either micropropagated or seedlings. On the other hand, fPSII decreased significantly in seedlings. The results suggest that the pre-acclimation, in pots, to external environmental conditions might have improved field survival, plant vigour and enhanced the endurance to adverse conditions of micropropagated carob trees

Evaluation of fruit and seed diversity and characterization of carob (Ceratonia siliqua L.) cultivars in Algarve region

The genetic diversity of 15 carob ( Ceratonia siliqua L.) cultivars located in an experimental field from Algarve (Portugal) was evaluated over 7 years using 12 fruit and seed phenotypic characters, in order to characterize carob cultivars. The values of morphological traits obtained by cultiv ar were compared with those from other countries of the Mediterranean basin. Statistically significant differences were found between cultivars for al l characters which were examined, what indicates a high genetic diversity. The relationship among these characters was analyzed by principal component analysis (PCA) resulting in the separation of these cultivars classed in four groups (clusters I–IV) and in four ungrouped cultivars. A three dimension of the model was found to be significant and explained 74.5% of the total variation, in which the first component accounting for 34.6% of the total variation is dominated by fruit characters, while the second component is dominated by seed characters. Cultivars plotted on the left-lower quadrant on the space determined by principal components 1 and 2 are characterized by fruits with high seed yield more appropriated for industrial rentability. The correlation analyses established by cultivar provided a specific understanding about the way how fruit and seed characteristics correlate within each cultivar. This approach can be useful for the development of a breeding programme, aiming to increase the seed yield, seed thickness, individual and total seed weight by fruit, characteristics that are determinant to improve the industrial exploitation of carob

Seasonal changes in CO2 assimilation in leaves of seedlings and micropropagated plants of Carob tree established in the field

In this communication we evaluate the field performance of two micropropagated Portuguese carob cultivars (Galhosa and Mulata) throughout the season, particularly at extreme conditions of light and temperature. Two irrigated plots were established in the field: 1) micropropagated plants, vs 2) seedlings. During the first year following transplantation to the field, we followed net photosynthetic rate, stomatal conductance, transpiration rate, chlorophyll a fluorescence and leaf contents in chlorophyll, carotenoids and protein. No significant differences were detected between seedlings and micropropagated plants along the year. However, at the end of summer, despite irrigation, the photosynthetic rate (NP), the quantum yield of PSII (fPSII) and the intrinsic efficiency of open PSII reaction centers (F’v/F’m) declined, concomitantly with the increase of the thermal energy dissipation at the PSII (NPQ). As the maximal photochemical efficiency of PSII (Fv/Fm) was maintained high (0.82), these results indicate that regulated thermal dissipation in light harvesting complexes was promoted in order to avoid photoinhibition. After the first growth period in the field, data from micropropagated plants did not differ from seedlings, and those plants showed the characteristic behaviour of plants well adapted to Mediterranean climates. So, in vitro propagation could be use as a promising alternative to traditional propagation and establishment of carob orchards

Photosynthetic responses of Lupinus albus to soil water fluctuations

Lupinus albus plants were grown in 3 dm3 pots in a semi-controled greenhouse. Two water regimes were imposed: water deficit (S, 47% of soil capacity), and control (T, 86% of soil capacity). Plants water status was monitored through foliar relative water content (TRA) and pre-dawn (ypd) and midday water potential (ymd). Gas exchanges, chlorophyll a fluorescence and photosynthetic capacity (Amax) were measured. Pigments and soluble protein were quantified and antioxidant system enzymes activity was determined. Plants under water deficit were rehydrated and the same measurements and sampling were done again after 48 h (R1) and 72 h (R2). Albeit water availability has diminished from 86% to 47% of soil capacity, there weren’t any remarkable changes on S plants. R1 plants which haven’t shown any alterations neither in Amax nor in stomatal conductance (gH2O), exhibited a significant decrease on net photosynthesis (A), reaching negative values, along with a raise in non-photochemical quenching (NPQ). Presumably this raise should be related with an increase in the xanthophyll cycle deepoxidation state. The significantly increase in Superoxide dismutase (SOD) specific activity in R1 and R2 plants might be related with the activation of Mehler-peroxidase reaction which provokes lumen DpH raising. This can provide photosynthesis protection through VAZ cycle and may justify the NPQ increase

Effects of soil drying and subsequent re-watering on the activity of nitrate reductase in roots and leaves of Helianthus annuus

The effects of drought on the activity of nitrate reductase (NR) were studied in Helianthus annuus L. plants subjected to soil drying and subsequent rewatering. Drought did not negatively affect the activation state of NR, but resulted in linearly correlated decreases in the activity of the unphosphorilated active form and the total activity of NR, both in roots and leaves. The concentration of nitrate in roots, xylem and leaves also decreased in waterstressed plants, whereas the concentration of total amino acids was only transiently depressed at the leaf level. In contrast, soluble sugars accumulated both in roots and leaves of waterstressed plants. Drought-induced decrease in root NR activity was correlated with the observed changes in root nitrate concentration. A higher percentage of the decrease in foliar NR activity could be explained by the decline in nitrate flux to the leaves than by leaf nitrate content. Following rewatering, the extent of recovery of NR activity was higher in roots than in leaves. The delay in the recovery of foliar NR activity did not result from the persistence of reduced flux of nitrate through the xylem. Several hypotheses to explain the after-effect of soil drying on foliar NR activity are discussed

Cultura em substratos orgânicos de Gerberas

O cultivo sem solo de Gerbera (Gerbera jamesonii) tem-se revelado uma técnica adequada, permitindo ultrapassar alguns dos problemas surgidos na cultura tradicional, em solo. No âmbito do Projecto Agro no197 “Cultura sem solo com reutilização do efluente, em estufa com controle ambiental melhorado”, desenvolvido pela Direcçao Regional de Agricultura do Algarve, pelo Cento de Hidroponia e Utilidades Hortofrutícolas e pela Universidade do Algarve testou-se o cultivo de gerbera em substratos alternativos, no Centro de Experimentação Hortofrutícola do Patacão. Cultivaram-se quatro cultivares de gerbera: Monika, Junkfrau, Venice e Lady, em substratos preparados à base de resíduos orgânicos: casca de pinho e bagaço de uva, durante dois anos consecutivos. Os resultados obtidos sugerem que os substratos testados apresentam características adequadas à cultura da gerbera, tendo-se obtido as produções mais elevadas com o bagaço de uva compostado e a casca de pinho não compostada. Das cv. em estudo, no 1o ano a Venice apresentou o maior número de flores comercializáveis, seguida da Lady com mais flores na classe Extra. No 2o ano, a produção foi mais equilibrada entre as cultivares, sendo de registar o aumento da produção em duas cv., Junkfrau e Monica

Influence of transient shade periods on the effects of drought on photosynthesis, carbohydrate accumulation and lipid peroxidation in sunflower leaves

The effects of a slow-imposing two-weeks soil drying period, and subsequent re-watering, on leaf water potential (Ψ), gas exchange rates, chlorophyll fluorescence and on the concentrations of malondialdehyde (MDA) and non-structural carbohydrates (starch, hexose and sucrose) were determined in mature leaves of sunflower plants growing under controlled environmental conditions. To assess how transient shade periods, associated with increased cloud cover, may influence drought-induced effects on carbon assimilation, measurements were carried out both in plants kept under the photosynthetic photon flux density (PPFD) prevailing during the growth period and stress imposition (750 μmol m-2 s-1), and in plants subjected to a 5 hours-long period under a lower PPFD (200 μmol m-2 s-1). In plants kept under high PPFD, Ψ, stomatal conductance (g), net CO2 uptake rate (A), the quantum yield of photosystem II electron transport (Φe), the photochemical efficiency of open PSII reaction centres (Fv’/Fm’) and * Corresponding author. Tel: +351 289800932; fax: +351 289818419. E-mail address: [email protected] (M.J. Correia) 1 the diurnal accumulation of total non-structural carbohydrates (TNC) were significantly depressed at the end of the soil drying period, whereas non-photochemical quenching (NPQ), the concentrations of MDA and the predawn pools of soluble sugars were found to increase. Under high-light level, drought-induced effects on lipid peroxidation, chlorophyll fluorescence parameters and gas exchange rates were fully reversed upon re-watering. However, the inhibition of diurnal accumulation of TNC still persisted two days following re-watering, suggesting that carbohydrate export rates were enhanced following stress relief. An overall positive effect was found upon transferring water-stressed plants to low light level, as indicated by the increases in Ψ, intrinsic water use efficiency (A/g), Φe and Fv’/Fm’, as well as the reversal of drought-induced enhancement of both NPQ and MDA concentration. Despite g being similar in shaded well-watered and re-watered plants, the latter exhibited net CO2 uptake rates below those found in well-watered leaves under the same light conditions, together with a diurnal decrease in the concentration of TNC that was mainly attributable to the depletion of starch and sucrose. These results indicate that contrasting with the positive effects of shading on water-stressed plants, low PPFD may negatively affect the recovery of net photosynthesis following stress relief

Light-dependent photosynthetic characteristics indicated by chlorophyll fluorescence in micropropagated plants of Rhododendron ponticum subsp baeticum during acclimation

Micropropagated plants of Rhododendron ponticum subsp. baeticum after acclimatization were grown in natural conditions at three levels of irradiance (HL = 1000, IL = 300 and LL = 80 mu mol m(-2) s(-1) using permanent shading. Light acclimation of photosynthesis was characterized using chlorophyll a fluorescence of intact leaves. There was a clear association between light acclimation of photosynthetic performance and growth irradiance. In general, the saturated electron transport rate, ETR, was higher for high (HL) and intermediate light (IL) than for low-light (LL) grown plants. The response of q(p), which represents PSII openness to incident light, indicates a ranking of tolerant capacity to photoinhibition of HL>IL>LL. The light acclimation of the non-radiative dissipation of excess energy in the antenna, q(N), was not very clear despite the highest value shown by HL plants. A clear feature of the light response of qp and qN is the gradual replacement of qp by qN with increasing light. However, this photoprotective strategy in LL plants seems to be less efficient than in HL plants. Moreover, after an exposition to strong light environment, the maximal photochemical efficiency of PSII (F-v/F-m) did not recover after 24 hours in IL and LL plants. This great plasticity of photosynthesis in R. ponticum plants indicates that the high light regimes during acclimation in the field can beneficiate the plant growth without photoinhibition effects