Energetics of maize C4 physiology under light limiting conditions
type: CreativeWork
description: C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around Rubisco in the bundle sheath (BS). Maize CCM has two CO2 delivery pathways to the Bundle Sheath (BS) (respectively via malate, MAL or aspartate, ASP); rates of PGA reduction, carbohydrate synthesis and PEP regeneration vary between BS and Mesophyll (M) cells. For these anatomical and biochemical complexities, C4 plants are highly sensitive to light conditions. Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. This increase in Φ had been theoretically associated with a decrease in biochemical operating efficiency (expressed as ATP cost of gross assimilation, ATP / GA) under low light and, because a proportion of canopy photosynthesis is carried out by shaded leaves, to potential productivity losses at field scale. In C4 leaves, because of the concentric anatomy, light reaches M cells before the deeper BS (Evans et al., 2007), and could alter the energetic partitioning balance between BS and M and potentially cause efficiency losses. In this experimental programme I investigated strategies deployed by C4 plants to adjust operating efficiency under different illumination conditions. Firstly, maize plants were grown under high and low light regimes (respectively HL, 600 vs LL, 100 μE m-2 s-1). Short term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry using an improved modelling approach which does not suffer from elements of circularity. Long term acclimation to low light intensities brought about physiological changes which could potentially increase the operating efficiency under limiting ATP supplies. Secondly, profiles of light penetration across a leaf were used to derive the potential ATP supply for M and BS cells induced by changing light quality. Empirical measurements of …
abstract: C4 plants have a biochemical carbon concentrating mechanism (CCM) that increases CO2 concentration around Rubisco in the bundle sheath (BS). Maize CCM has two CO2 delivery pathways to the Bundle Sheath (BS) (respectively via malate, MAL or aspartate, ASP); rates of PGA reduction, carbohydrate synthesis and PEP regeneration vary between BS and Mesophyll (M) cells. For these anatomical and biochemical complexities, C4 plants are highly sensitive to light conditions. Under limiting light, the activity of the CCM generally decreases, causing an increase in leakiness, (Φ), the ratio of CO2 retrodiffusing from the BS relative to C4 carboxylation processes. This increase in Φ had been theoretically associated with a decrease in biochemical operating efficiency (expressed as ATP cost of gross assimilation, ATP / GA) under low light and, because a proportion of canopy photosynthesis is carried out by shaded leaves, to potential productivity losses at field scale. In C4 leaves, because of the concentric anatomy, light reaches M cells before the deeper BS (Evans et al., 2007), and could alter the energetic partitioning balance between BS and M and potentially cause efficiency losses. In this experimental programme I investigated strategies deployed by C4 plants to adjust operating efficiency under different illumination conditions. Firstly, maize plants were grown under high and low light regimes (respectively HL, 600 vs LL, 100 μE m-2 s-1). Short term acclimation of Φ was compared from isotopic discrimination (Δ), gas exchange and photochemistry using an improved modelling approach which does not suffer from elements of circularity. Long term acclimation to low light intensities brought about physiological changes which could potentially increase the operating efficiency under limiting ATP supplies. Secondly, profiles of light penetration across a leaf were used to derive the potential ATP supply for M and BS cells induced by changing light quality. Empirical measurements of …
author: Bellasio, Chandra
language: en
keywords: photosynthesis, carbon reduction, energetics, shade, C4, light quality, biochemistry, light penetration, model, carbon isotope discrimination, leakiness, bundle sheath
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/321b7b5d-94bd-4174-87c4-740041d6173a/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2014-07-01
date modified: 2026-07-22T22:24:24Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.16453