Changes in chloroplastidic pigments, gas exchange and carbohydrate concentrations were assessed during the rapid initial expansion of C. guianensis leaflet. Leaves at metaphyll stage were tagged and assessments were carried out 14, 17, 20, 23, 27, and 31 days later. Pigments synthesis, distribution and accumulation were uniform among leaflet sections (basal, median and apical). Chlorophyll (Chl) a, Chl b, Chl (a+b), and total carotenoids (Car) concentrations were significantly increased after 27 days from metaphyll, and the most expressive increases were parallel to lower specific leaflet area. Chl a/b was lower on day 14 and it was increased on subsequent days. Negative net photosynthesis rate (PN), and the lowest stomatal conductance (gs) and transpiration (E) were registered on day 14, following significant increases on subsequent days. The Chl (a+b) and Chl a effects on PN were more expressive until day 20. Intercellular to ambient CO2 concentration ratio (Ci/Ca) was higher on day 14 and lower on subsequent days, and no stomatal limitation to CO2 influx inside leaflets was observed. Leaflet temperature was almost constant (ca. 35°C) during leaflet development. Sucrose and starch concentrations were increased in parallel to increases in PN. Altogether, these results highlight the main physiological changes during C. guianensis leaflet expansion and they should be considered in future experiments focusing on factors affecting PN in this species. and F. K. C. Moraes ... [et al.].
The four Fabaceae species of different chilling tolerance (Pisum sativum L., Glycine max. Merr., Phaseolus vulgaris L. and Vigna unguiculata L.) were subjected to simulated bad weather periods at the beginning of the growth season. The treatment parameters were 14 d at constant 10 “C, 100 pmol m-2 s"*, 80 % relative humidity within a 12 h photoperiod. During chilling and subsequent recovery, photosynthesis, chlorophyll fluorescence and assimilate concentrations, as well as ribulose-1,5- bisphosphate carboxylase/oxygenase (RuBPCO) activity were followed. Despite the observation that no significant photoinhibition had been induced by the treatment, French beán and cowpea showed a strong decrease of photosynthetic capacity within the first week. Diuring chilling, soybean, French beán and cowpea virtually did not grow fiirther, but acciunulated large amounts of starch, in contrast to pea. Specific activity of RuBPCO (Mg2+- and HC03'-activated) was not altered significantly by the chilling treatment. Yet in French beán a generál protein breakdovm occurred in the second week. At the same time, a very strong decrease of qp was obtained in this species, indicating a breakdown of the electron transport. Pea and soybean were not negatively afifected by the long-term chilling.