摘要:

ABSTRACTTwo tropical trees,Acacia confusaandLitsea glutinosa, were grown under controlled conditions with their roots subjected to soil drying and soil compaction treatments. In both species, a decline in stomatal conductance resulting from soil drying took place much earlier than the decline of leaf water potential. Soil compaction treatment also resulted in a substantial decrease in stomatal conductance but had little effect on leaf water potential. A rapid and substantial increase in xylem abscisic acid (ABA) concenation ([ABA]), rather than hulk leaf ABA, was closely related to soil drying and soil compaction. A significant relationship between stomatal conductance (gs) and xylem [ABA] was observed in both species. Artificially feeding ABA solutions to excised leaves of both species showed that the relationship bet ween gsand [ABA] was very similar to that obtained from the whole plant, i.e. the relationship between gsand xylem [ABA]. These results suggest that xylem ABA may act as a stress signal in the control of stomatal conductance.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00230.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWe assessed whether growth of garden pea (Pisum sativummutantArgenteum) was reduced under ecologically relevant enhancements of ultraviolet‐B radiation (UV‐B, 280–320 nm) by employing modulated field lampbanks which simulated 0, 16 or 24% ozone depiction. In addition, we determined whether enhanced UV‐B altered the concentration and distribution of chlorophyll and UV‐B‐absorbing compounds in leaves, and whether this was dependent on leaf age. There were no significant UV‐B effects on the four whole‐plant parameters we examined (height, above‐ground biomass, total leaflet area or average leaflet area). Of the 12 leaf‐level parameters we examined, UV‐B had a significant effect (P<0.05) on only one parameter: the ratio of UV‐B‐absorbing compounds to chlorophyll, which was greatest at the highest UV‐B level. Total chlorophyll concentrations tended to be lower under enhanced UV‐B (P= 0.11), while the proportion of UV‐B‐absorbing compounds in the adaxial epidermis tended to be higher (P= 0.11). Total leaf concentrations of UV‐B‐absorbing compounds were unaffected by UV‐B level. Cooler, suboptimal growing conditions during this late summer/early autumn experiment may have masked some potential UV‐B effects. In contrast to the UV‐B effects, we found strong leaf‐age effects on nearly all parameters that we assessed. On an area basis, concentrations of total chlorophyll and UV‐B‐absorbing compounds increased with leaf age, while Chlorophyll a/b) ratios decreased. One of the few parameters unaffected by leaf age was the ratio of UV‐B‐absorbing compounds to total chlorophyll, which remained constant within a given UV‐B treatment. Pea was much less sensitive to enhanced UV‐B than in previous growth‐chamber and greenhouse studies, and in nearly all cases UV‐B treatment effects were overshadowed by leaf‐age effects. In view of the large effect leaf age had on concentrations of UV‐B‐absorbing compounds, as well as their distribution within leaves, res

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00231.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTResource allocation in high CO2was studied with respect to plant nutrition. Pea (Pisum sativum) was grown in CO2‐enriched air (1000 cm3m3CO2) during the entire vegetative phase, or grown in ambient air (340 cm3m3CO2), with different levels of nitrogen or phosphorus supply. Rubisco specific activity, abundance and small subunit transcript levels were unaltered at high N but declined at reduced N depending upon the degree of N deprivation. It is proposed that (a) a threshold value for the N status occurs in pea above which Rubisco is not down‐regulated by high CO2and (b) a high leaf level of soluble carbohydrates is not a sufficient condition to downregulate Rubisco in high CO2. Phosphoenolpyruvate (PEP) carboxylase decreased, and chloroplast phosphate (P)‐translocator increased, in high CO2. In contrast to Rubisco, down‐regulation of PEP carboxylase was alleviated by low N and enhanced by low P. The increase in the P‐translocator was little affected by N but was accentuated by low P. The increase in the P‐translocator is considered to be one way of alleviating low P conditions in the chloroplast and thus rebalancing carbon partitioning between starch and soluble carbohydrates and amino acids. It is proposed that acclimation of PEP carboxylase and P‐translocator reflects adaptation to metabolic perturbations cause

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00232.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe relative effect of diffusional resistance due to water films (rwf) and leaf anatomy (rp) on rates of net photosynthesis and on‐line measures of carbon isotope discrimination (Δ=Δδ13C) was investigated inSphagnum. Sphagnumspecies differ in the exposure of photosynthetic cells at the leaf surface. InS. affine, photosynthetic cells are widely exposed at the surface, whereas inS. magellanicum, photo‐synthetic cells are enclosed within water‐filled hyaline cells. This difference is expected to lead to variation in diffusive resistance within leaves (rp). Net photosynthesis and on‐line Δ were measured at two water contents: greenhouse water content (wet) and blotted dry (dry). Without correcting for respiration, on‐line Δ values differed significantly between wet (23.7%o) and dry (30.9%o) plants. However, there was no significant difference between species means and no species × water content interaction. Corrections for respiration lowered Δ values by approximately 8.1%oand reduced the mean difference to 3.1%o, but did not alter the rank order of treatments. Net photosynthesis also decreased by 16% in wet plants, but there was no significant difference between the two species. In addition, five populations ofS. affineandS. magellanicumgrown in a common garden were analysed for their organic matter carbon isotope composition (δ13C). These values varied more within each species (0.9–1.2%o) than between the two species (0.6%o). Therefore, we conclude that variation in surface water films leads to a greater difference in resistance to CO2uptake and carbon isotope discrimination than that due to variation in leaf anatomical pr

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1996.tb00233.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY