Constable, John , Dhah, Satinderpal .
Sexual reproduction in Podophyllum peltatum (Mayapple): Meeting carbon requirements through differences in leaf area and gas exchange characteristics.
IN the ephemeral understory species Podophyllum peltatum (Mayapple), a single leaf supports vegetative (V) ramets, whereas reproductive (R) ramets are supported by two leaves. This study hypothesized that in R ramets, the increased carbon gain due to leaf area are supplemented by increased photosynthetic activity relative to V ramets. V and R rhizomes (n=6-11) were grown at ~550 µmolm-2s-1 illumination and responses to light and CO2 were measured weekly using an LI-6400 gas exchange system. A repeated measures ANOVA was used to analyze the effect of leaf type (V or R) and leaf age on photosynthetic responses. Averaged across the season, V leaves had a Rubisco carboxylation rate (Vcmax) of 33.4±3.8 µmolm-2s-1, electron transport rate (Jmax) of 94.8±10.0 µmolm-2s-1, respiration rate (Rd) of 0.64±0.06 µmolm-2s-1, light-saturated photosynthetic rate (Amax) of 7.40±0.63 µmolm-2s-1, light saturation point (LSP) of 117±10 µmolm-2s-1, light compensation point (LCP) of 10.2±1.3 µmolm-2s-1, and an apparent quantum efficiency (QE) of 0.069±0.001 (unitless). Relative to V leaves, R leaves had 38% greater Vcmax (P=0.0004), 40% greater Jmax (P=0.0003), 36% greater Rd (P=0.0273), 50% greater Amax (P=0.0001), 42% greater LSP (P=0.0358), and 8% greater AQE (P=0.0283), but LCP (P=0.5063) was not affected. All parameters, except LSP, were affected by time and only LCP exhibited an interaction effect (P=0.0414). The hypothesis that physiological differences supplement enhanced leaf area in meeting R ramet carbon requirements relative to V ramets is supported. Illumination conditions during leaf development are expected to alter the balance between the structural and physiological components of carbon gain in R ramets. Early emerging leaves develop in high light therefore both structural and physiological components contribute to carbon gain. However, later emerging leaves develop in lower light potentially constraining the role of the physiological component in contributing to R ramet carbon gain.
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1 - California State University, Department of Biology, 2555 East San Ramon Ave. M/S SB73, Fresno, California, 93740-8034, USA
Presentation Type: Poster:Posters for Sections
Location: Auditorium/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 12:30 PM