Trocas gasosas e fluorescência da clorofila em seis cultivares de cafeeiro sob estresse de alumínio Gas exchange and chlorophyll fluorescence in six coffee cultivars under aluminum stress

Em experimento desenvolvido em casa de vegetação e em câmara de crescimento avaliou-se o efeito do alumínio (Al) na fotossíntese de seis cultivares de cafeeiro. As plantas foram cultivadas em solução nutritiva aerada continuamente, contendo duas concentrações de Al, 0 e 0,148 mmol L-1, fornecidas como Al2(SO4)3. Após 97 dias mediram-se as taxas de assimilação de CO2 (A) e transpiração (E), a condutância estomática (gs), a concentração interna de CO2 (Ci), eficiência instantânea de carboxilação (fic) e variáveis de fluorescência da clorofila. Em todas as cultivares, a presença de Al causou quedas significantes em A, gs, fic, ocorrendo aumento em Ci. Também se observou aumento significativo na fluorescência basal (Fo) e queda na eficiência quântica máxima do fotossistema II (Fv/Fm), sugerindo injúrias na estrutura dos tilacóides causadas pelo Al. Na curva de indução de fotossíntese, observou-se que o Al causou queda no coeficiente de extinção fotoquímica da fluorescência e aumento no coeficiente de extinção não fotoquímico. Os resultados desse estudo indicaram que a queda de A foi devida à queda da condutância estomática, nas atividades bioquímicas e fotoquímicas.<br>Experiments were carried out under greenhouse and growth chamber to evaluate the effects of aluminum (Al) on several photosynthetic characteristics in six coffee cultivars. Plants were grown in nutrient solution aerated continuously, containing two Al concentration, 0 and 0.148 mmol L-1, supplied as Al2(SO4)3. After 97 days of treatament, measurements of CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (gs), internal CO2 concentration (Ci), instantaneous carboxylation efficiency (phic) and chlorophyll fluorescence related characteristics were performed. All six cultivars showed decrease in A, gs and phic and increase in Ci. The basal chlorophyll fluorescence yield (Fo) increased and the maximum quantum efficiency (Fv/Fm) decreased suggesting structural damage in thylakoid. The photosynthetic induction curve revealed that Al caused decreases in photochemical quenching of fluorescence as well as increases of non-photochemical quenching. Our results indicated that A reduction was related to decreases in both stomatal conductance, and biochemical and photochemical damages

Forecasted Stability of Mediterranean Evergreen Species Considering Global Changes

Plant communities of the Mediterranean climate Regions are exposed to high temperatures, high radiation and water stress during summer, they are dominated by evergreen sclerophyllous species and drought semi deciduous species. To define the adaptive strategies, anatomical and morphological leaf traits of Quercus ilex L., Phillyrea latifolia L. (typical evergreen sclerophyllous species) and Cistus incanus L., (a drought semi deciduous species), growing in the Mediterranean maquis along Pome's coast line (Italy) were analysed. The typical evergreen sclerophyllous species have long leaf life span (from 1 to 4 years), steeper leaf inclination (average 56 degrees), higher specific leaf mass (average 21.3 mg cm(-2)) and the highest leaf thickness (average 324 mum). The semi deciduous species have a lower leaf life span (from 4 to 8 months), a lower leaf inclination (44 degrees +/- 13 degrees), a lower specific leaf mass (14.7 +/-1.5 mg cm(-2)) and a lower leaf thickness (244 +/- 15 mum). The more xeromorphyc species (Q. ilex and P. latifolia) may be at a competitive advantage considering the forecasted air temperature increase in the Mediterranean basin. Increasing drought stress may in fact determine a shortening of leaf life span that may prove to be critical for C. incanus. Knowledge of plant response to stress factors is important in the perspective of climatic changes

Slow-release and organic fertilizers on early growth of Rangpur lime

Slow-release and organic fertilizers are promising alternatives to conventional fertilizers, as both reduce losses by leaching, volatilization and problems of toxicity and/or salinity to plants. The objective of this work was to evaluate the effect of different rates of the organic fertilizer Humato-Macota® compared with the slow-release fertilizer Osmocote® on the growth and nitrogen content in the dry matter of Rangpur lime. A field experiment was conducted in a factorial completely randomized design with an additional treatment (4 x 4 +1). The first factor consisted of four Humato­Macota® rates (0, 1, 2, and 3%) applied to the substrate; the second factor consisted of the same Humato-Macota® concentrations, but applied as fortnightly foliar sprays; the additional treatment consisted of application of 5 kgm-3 Osmocote® 18-05-09. Means of all growth characteristics (plant height, total dry matter, root/shoot ratio and leaf area) and the potential quantum yield of photosystem II (Fv/Fm) were higher when plants were fertilized with the slow-release fertilizer. The organic fertilizer applied alone did not meet the N requirement of Rangpur lime

Carob trees (Ceratonia siliqua L.) regenerated in vitro can acclimatize successfully to match the field performance of seed-derived plants

The use of in vitro regenerated plants in forestry and orchard depends ultimately on the development of efficient transplantation protocols, ensuring high survival rates and successful establishment under field conditions. We tested the performance of micropropagated carob trees (Ceratonia siliqua L.) throughout the acclimatization process in terms of survival, growth and physiological traits, including field comparisons with seed-derived and mother plants. The field trial was 100 %successful, i.e. we found no major differences between micropropagated, seed-derived and mother plants in terms of growth rate, height, number of leaves, photosynthetic efficiency, chlorophyll fluorescence, chlorophyll content and soluble protein content, although these parameters changed significantly during acclimatization. Stomatal conductance (gs) was reduced by fourfold when plants were transferred from in vitro culture to the growth chamber, thus preventing uncontrolled wilting. The photosynthetic rate (PN) was relatively low in vitro, in the growth chamber and the greenhouse, but increased to match seed-derived and mother plants in the field. The chlorophyll a/b ratio in leaves from in vitro and growth chamber plants was typical of shade plants (2.1) but became more characteristic of sun plants in the subsequent acclimatization stages (3.1–3.5). The maximum efficiency of photosystem II (Fv/Fm) remained mostly constant at ~0.80 throughout acclimatization, as is typical for healthy, non-stressed plants. We conclude that our micropropagation and acclimatization protocols provide a suitable alternative to traditional mass propagation techniques for the carob tree.M.L. Osório and S. Gonçalves acknowledge a grant from the Portuguese Science and Technology Foundation (FCT, Grant SFRH/BPD/35410/2007 and SFRH/BPD/31534/2006