Potted cuttings of three Eucalyptus globulus Labill. clones (AR3, CN44, MP11) were either well watered or subjected to one of two soil water deficit regimes for six months in a greenhouse. Reductions in lateral branching, leaf production and leaf expansion were the leading contributors to the large differences observed in biomass production between well-watered and water-stressed plants. Although no significant differences among clones were observed in dry matter accumulation or in the magnitude of the response to soil water deficits, sensitivity of lateral branching, leaf initiation and whole-plant foliage to water stress was significantly lower in CN44 than in AR3 and MP11. When the confounding effect of differences in plant size resulting from the different watering regimes was removed, allometric analysis indicated that the genotypes differed in biomass allocation patterns. In addition to a drought-induced reduction in leaf number, water deficits also resulted in smaller leaves because leaf expansion was inhibited during dehydration events. Resumption of leaf expansion following stress relief occurred in all of the clones, but was particularly evident in severely stressed plants of Clone AR3, possibly as a result of the osmotic adjustment observed in this genotype.

Cuttings of three Eucalyptus globulus Labill. clones (called SM, VC, DG henceforward) were grown for 56 days in 10-l pots in a greenhouse. Every other day, eight pots of each clone were watered to field capacity (HW treatment), whereas the other eight pots of each clone received only 25% of the water needed to maintain the soil at field capacity (LW treatment). Transpirational water loss, biomass production, leaf gas exchange and water potential (at predawn and midday) were determined at different times during the experiment. Leaf tissue formed by the LW plants after the onset of the treatment was analyzed for (13)C/(12)C ratio against the PeeDee Belemnite standard (delta(13)C). The three clones differed significantly in growth capacity (SM > DG > VC) and in their response to water stress. Even though leaf water potentials were not significantly modified by withholding water, total biomass and plant leaf area were affected significantly by soil water deficits by the end of the experiment. The fastest growing clone (SM) was the most affected by water deficit. Long-term water use efficiency (i.e., biomass per unit of water transpired, WUE) was significantly increased by water deficit and was positively correlated with delta(13)C. Long-term WUE was well correlated with the quotient of the daily integrals of carbon assimilation rate and stomatal conductance. The value of delta(13)C was negatively correlated with the variables normally positively related with growth, such as specific leaf area (SLA) and the biomass/intercepted light quotient (epsilon), and it was positively related to the amount of carbon per unit leaf area, which is usually negatively correlated with relative growth rate.

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 cultivar were compared with those from other countries of the Mediterranean basin. Statistically significant differences were found between cultivars for all 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. #

Potted cuttings of three Eucalyptus globulus Labill. clones (AR3, CN44, MP11) were grown over 6 months in a greenhouse under three watering regimes: well watered (HW), moderate soil water deficit (MS) and severe soil water deficit (SS). Transpiration efficiency (W = total dry matter/water transpired) and leaf intrinsic gas exchange efficiency (A/gs = carbon assimilation rate/stomatal conductance) increased under water stress and were positively correlated with the stable carbon isotope composition of leaf tissue (δ13C). The clones did not vary significantly with respect to A/gs and W. However, statistically significant differences were detected among clones in δ13C, A and biomass. W did not differ between the MS and SS regimes, probably due to plant acclimation to increasing soil water deficits. The increase in W with soil water deficits relative to the well watered control was primarily associated with stomatal closure, but was also influenced by differences in respiratory carbon losses (?c) and variation in the leaf-to-air water vapour difference (v). Variance in ?c and v may explain partially why the two levels of soil water deficit were different in regard to δ13C but not in terms of W.

The authors aknowledge Environmental and Experimental Botany, an Elsevier Journal. AbstractThe 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