The leaf carbon budget of salt-stressed olive plants

The carbon budget of fully-expanded leaves was calculated from diurnal profiles of gas exchange in one-year-old olive (Olea europaea L. cvs. Frantoio and Leccino) plants growing in soil culture and treated with 100 mM NaCI (external solution) for seven weeks. Daily leaf photosynthetic uptake of control plants was 0.375 and 0.520 mol CO2 m-2 leaf area over the 14.5 h light period for 'Frantoio and Leccino' respectively, whereas respiratory losses during the night period were 0.104 and 0.068 mol CO 2 m-2 for the same two cultivars. The daily carbon gain of stressed leaves was 63 and 42% of the controls in 'Frantoio" and Leccino" respectively. After seven weeks of stress, leaf maintenance payments were 9-17% and 23-29% of daily carbon gain in control and salt- treated plants of the two cultivars respectively. The expense of leaf growth was estimated as 14-44% of the daily carbon gain in control plants, whereas leaf growth required 34- 72% of the daily carbon gain of current seasons leaves in salt-stressed plant

Contrasting effects of elevated CO2 on the root and shoot growth of four native herbs commonly found in chalk grassland

The aim of this study was to investigate the impact of ambient (345 ?l l?1) and elevated (590 ?l l?1) CO2on the root and shoot growth of four native chalk grassland herbs: Sanguisorba minor Scop, (salad burnet), Lotus carniculatus L. (birdsfoot trefoil), Anthyllis vulneraria L. (kidney vetch) and Plantago media L. (hoary plantain).Elevated CO2 had contrasting effects on both shoot and root growth of the four species studied. Both leaf expansion and production were stimulated by elevated CO2 for S. minor, L. corniculatus and P. media, whilst for A. vulneraria, only leaflet shape appeared to be altered by elevated CO2, with the production of broader leaflets, compared with those produced in ambient CO2. After 100 d shoot biomass was enhanced in elevated CO2 for S. minor and L. corniculatus, whilst there was no effect of elevated CO2 on shoot biomass for A. vulneraria or P. media. Contrasting effects of CO2 were also apparent for measurements of specific leaf area (SLA), which increased for L. corniculatus, decreased for A. vulneraria and remained unaltered for S. minor and P. media in elevated compared with ambient CO2.Elevated CO2 also had contrasting effects on both the growth and morphology of roots. The accumulation of root biomass was stimulated following exposure to elevated CO2 for S. minor and L. corniculatus whilst there was no effect on root biomass for A. vulneraria or P. media. Root length was measured on three occasions during the 100 d and revealed that exposure to elevated CO2 promoted root extension in S. minor, L. corniculatus and P. media, but not in A. vulneraria. Specific root length (SRL, length per unit dry weight) was increased in elevated CO2 for one species, P. media, whilst the root to shoot ratio of all four species remained unchanged by CO2.These results show that four native herbs differ in their response to CO2, suggesting that the structure of this plant community may be altered in the future