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

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

A arquitectura paisagista como vector para a ecologia. O aparecimento do pensamento ecológico em Portugal

Mestrado em Arquitectura Paisagista - Instituto Superior de Agronomia - ULA hipótese deste trabalho admite um crescendo de preocupações ecológicas trazido para a esfera do projeto através da profissão da Arquitectura Paisagista e concentra-se nos projectos de espaços exteriores e ordenamento do território entre as décadas de 40 e de 90, produzidos na área profissional de Arquitectura Paisagista, sendo este talvez o período em que se verificou maior crescimento na aplicação do pensamento ecológico ao projeto. O projecto que marca a mudança de paradigma no tratamento da paisagem em Portugal é o projecto ao qual Francisco Caldeira Cabral se juntou em 1940 para a construção do Estádio Nacional no Vale do Rio Jamor. A partir desse projecto seminal são apresentados 50 anos de projectos que representam a crescente preocupação ecológica sugerida como hipótese neste trabalho terminando com o exemplo dos trabalhos de arquitetura paisagista da Parque Expo ‘98. As fontes de estudo apresentadas são as memórias descritivas de cerca de 70 jardins e parques de Portugal de onde são selecionados exemplos para cada uma das cinco décadas desde o início da arquitectura paisagista em Portugal até ao fim do séc. XX. A preocupação com o meio ambiente é uma constante tomada como objectivo nestas memórias descritivas deixadas pelos projectistas que serviram de base para o nosso estudo e permitiram confirmar através da análise dos diferentes projectos que o principal enfoque dos projetos centra-se em soluções ecológicas pioneiras na pratica projectual em Portugal resultando na protecção e defesa da paisagem concluindo-se que os Arquitectos paisagistas estão dentro das primeiras profissões que actuaram na defesa do ambienteN/

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

Photosynthesis, energy partitioning, and metabolic adjustments of the endangered Cistaceae species Tuberaria major under high temperature and drought

In view of predicted climatic changes for the Mediterranean region, study of high temperature and drought impacts on physiological responses of endangered species regains relevance. In this context, micropropagated plants of Tuberaria major, a critically endangered species, endemic of Algarve, were transferred to a controlled-environment cabinet with day/night temperatures set at 25/18A degrees C (Reference) or 32/21A degrees C (HT). After 15 days of HT acclimation, some plants were subjected to progressive drought followed by rewatering. The enhancement of temperature alone did not affect water relations and photosynthetic rates (P (N)) but the stomatal conductance (g (s)) exhibited a 3-fold increase in comparison with reference plants. The maximum quantum yield of photosystem (PS) II (F-v/F-m), the effective quantum yield of PSII photochemistry (I broken vertical bar(PSII)), carotenoid (Car) and anthocyanin content enhanced, whereas the quantum yields of regulated (I broken vertical bar(NPQ)) and nonregulated (I broken vertical bar(NO)) energy dissipation decreased. Drought combined with HT reduced predawn leaf water potential to values of about -1.3 MPa, which had adverse effects on gas exchange and PSII activity. Values of P (N) and g (s) were 71 and 79% lower than those of HT plants. An impairment of photochemical activity was also observed: the decrease in I broken vertical bar(PSII) and the increase of I broken vertical bar(NPQ). However, an irreversible photoinhibitory damage had not occurred. Carotenoid and anthocyanin content remained elevated and soluble sugars (SS) increased twice, whereas proline and MDA accumulation was not detected. On the first 24 h after water-stress relief, g (s), P (N), I broken vertical bar(PSII), and I broken vertical bar(NPQ) did not recover, but SS returned to the reference level. Overall, T. major acquired an adequate capacity for a protection against the development of oxidative stress during drought and water recovery under HT. These findings suggest that T. major is prepared to deal with predicted climate changes

Reflectance indices as nondestructive indicators of the physiological status of Ceratonia siliqua seedlings under varying moisture and temperature regimes

We investigated the use of spectral reflectance techniques to monitor the physiological responses of Ceratonia siliqua L. seedlings exposed to different levels of water availability under normal (25 : 18 degrees C, day : night) and elevated (32 : 21 degrees C, day : night) temperatures. Three spectral reflectance indices (photochemical reflectance index, PRI; water index, WI; red edge position, REP) were measured along with water status, chlorophyll fluorescence and chlorophyll concentration variables in the leaves of well watered, moderately stressed, severely stressed and rehydrated plants under each temperature regime. The PSII effective photochemical efficiency (phi(2)) and the intrinsic efficiency of open PSII centres (F-v'/F-m') correlated significantly with PRI, and these three variables loaded heavily onto the same principal component of a three-factor principal component analysis solution. Water concentration (WC) and the succulence index (SI) were more strongly correlated with WI than either water potential (Psi(PD)) or relative water content (RWC). Accordingly, WI, WC and SI were combined in the second principal component, and Psi(PD) and RWC in the third. Our results provide clear evidence for interaction between water availability and temperature in the WI and the PRI response segments of the reflectance curves. Elevated temperature inhibited the recovery of WI spectral segments more than that of the PRI segments in SS plants. REP showed a strongly positive linear relationship with leaf total chlorophyll concentration across all water and temperature treatment combinations. PRI, WI and REP are therefore reliable markers that can be used to monitor phi(2), WC and total chlorophyll concentration, respectively, in C. siliqua seedlings under drought and temperature stress

Effects of CO2 concentration on acclimatization and physiological responses of two cultivars of carob tree

This study reports survival and physiological responses of micropropagated Ceratonia siliqua L. cvs. Galhosa and Mulata plants during ex vitro acclimatization under ambient (AC; 330 μmol mol-1) or elevated (EC; 810 μmol mol-1) CO2 concentration and a photosynthetic photon flux density of 125 μmol m-2 s-1. CO2 enrichment during acclimatization did not improve survival rate that was around 80 % for both treatments. Eight weeks after ex vitro transplantation, photosynthetic capacity and apparent quantum yield in acclimatized leaves were higher in comparison with those in in vitro-grown leaves, without any significant difference between CO2 treatments. Chlorophyll content increased after acclimatization. However, EC led to a decrease in the total amount of chlorophyll in new leaves of both cultivars, compared to those grown at AC. Soluble sugars and starch contents were not markedly affected by growth EC, although starch had significantly increased after transfer to ex vitro conditions. EC induced an increase in the stem elongation and in the effective life of leaves, and a decrease in the number of new leaves

The effects of drought on net CO2 uptake, chlorophyll fluorescence and photosynthetic pigments in mature and young leaves of sunflower

Photosynthesis, photosystem II activity and photosynthetic pigments were analysed in mature and Young leaves of sunflower (Helianthus annuus L.) during dehydration and rehydration, in order to determine the influence of leaf age on the sensitivity to drought. Dehydration caused a more pronounced inhibition in photosynthetic rates in mature leaves compared to younger leaves, but 24 h after rewatering the recovery was complete in spite of leaf age. After exposure to drought, mature leaves showed a larger reduction in the actual PSII photochemical efficiency and a higher increase in nonradiative energy dissipation than young leaves. In well-watered plants the de-epoxidation level represented by the ratio A+Z/V+A+Z was higher in young leaves. However drought had opposite effects on both type of leaves: in young leaves A+Z/V+A+Z decreased with water deficit, while in mature leaves increased with soil drying. The results obtained suggest that leaf age influence the “strategy” to avoid irreversible damage of PSII activity under drought and that older leaves are more drought-sensitive than younger leaves of sunflower