Ozone impact on vegetation: A primary lesion in sugar export from source leaves

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20002256

Grantz, D A

Ozone (O{sub 3}) remains a serious threat to native and agricultural vegetation. In many plants, including Pima cotton (Gossypium barbadense L.), O{sub 3} reduces development of efficient root systems. To investigate the mechanism of O{sub 3}-inhibited allocation of biomass to roots, leaves were exposed to 45 min pulses of O{sub 3} ranging from 0.0 to 0.8 {micro}l 1{sup 11} followed by a 15 min pulse of {sup 14}CO{sub 2}. The rapid phase of export of {sup 14}C-carbohydrate from source leaves was monitored with a Geiger Muller Tube. A single compartment model with a single exponential decay function yielded first order rate constants. O{sub 3} retarded efflux, decreased the rate constant, and increased the calculated soluble sugar pool remaining in the source leaves. With incorporation of an asymptote into the single exponential model, equivalent to the label remaining in the leaf at the end of a prolonged photoperiod, calculated rate constants and sugar contents for O{sub 3}-free control leaves were similar to values from the literature. Total carbohydrate transported from source leaves and thus available for export to the roots was reduced by O{sub 3} effects on assimilation (up to 20%) and O{sub 3} effects on efflux (up to 70%). O{sub 3}-inhibition of root system development is therefore dominated by the impact on phloem translocation rather than by effects on carbon assimilation.

• Research Organization: Univ. of California, Parlier, CA (US)
• OSTI ID: 20002256
• Report Number(s): CONF-990608--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
56 BIOLOGY AND MEDICINE
APPLIED STUDIES
AIR POLLUTION
BIOLOGICAL EFFECTS
COTTON
ENVIRONMENTAL IMPACTS
LEAVES
OZONE
PHOTOSYNTHESIS