AOBPreview originally published online on November 30, 2006
Annals of Botany 2007 99(2):255-263; doi:10.1093/aob/mcl252
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Effects of Kaolin Application on Light Absorption and Distribution, Radiation Use Efficiency and Photosynthesis of Almond and Walnut Canopies
1 Istituto Sperimentale per l'Olivicoltura, via Nursina 2, 06049 Spoleto (PG), Italy
2 Department of Plant Sciences, University of California, Mail Stop #2, One Shields Avenue, Davis, CA 95616, USA
3 University of California Cooperative Extension, Tehama County, 1754 Walnut Street, Red Bluff, CA 96080, USA
* For correspondence. E-mail adolfo.rosati{at}entecra.it
Received: 29 May 2006 Returned for revision: 16 August 2006 Accepted: 16 October 2006 Published electronically: 30 November 2006
BACKGROUND AND AIMS: Kaolin applied as a suspension to plant canopies forms a film on leaves that increases reflection and reduces absorption of light. Photosynthesis of individual leaves is decreased while the photosynthesis of the whole canopy remains unaffected or even increases. This may result from a better distribution of light within the canopy following kaolin application, but this explanation has not been tested. The objective of this work was to study the effects of kaolin application on light distribution and absorption within tree canopies and, ultimately, on canopy photosynthesis and radiation use efficiency.
METHODS: Photosynthetically active radiation (PAR) incident on individual leaves within the canopy of almond (Prunus dulcis) and walnut (Juglans regia) trees was measured before and after kaolin application in order to study PAR distribution within the canopy. The PAR incident on, and reflected and transmitted by, the canopy was measured on the same day for kaolin-sprayed and control trees in order to calculate canopy PAR absorption. These data were then used to model canopy photosynthesis and radiation use efficiency by a simple method proposed in previous work, based on the photosynthetic response to incident PAR of a top-canopy leaf.
KEY RESULTS: Kaolin increased incident PAR on surfaces of inner-canopy leaves, although there was an estimated 20 % loss in PAR reaching the photosynthetic apparatus, due to increased reflection. Assuming a 20 % loss of PAR, modelled photosynthesis and photosynthetic radiation use efficiency (PRUE) of kaolin-coated leaves decreased by only 6·3 %. This was due to (1) more beneficial PAR distribution within the kaolin-sprayed canopy, and (2) with decreasing PAR, leaf photosynthesis decreases less than proportionally, due to the curvature of the photosynthesis response-curve to PAR. The relatively small loss in canopy PRUE (per unit of incident PAR), coupled with the increased incident PAR on the leaf surface on inner-canopy leaves, resulted in an estimated increase in modelled photosynthesis of the canopy (+9 % in both walnut and almond). The small loss in PRUE (per unit of incident PAR) resulted in an increase in radiation use efficiency per unit of absorbed PAR, which more than compensated for the minor (7 %) reduction in canopy PAR absorption.
CONCLUSIONS: The results explain the apparently contradictory findings in the literature of positive or no effects of kaolin applications on canopy photosynthesis and yield, despite the decrease in photosynthesis by individual leaves when measured at the same PAR.
Key words: Juglans regia, kaolin particle film, modelling, photosynthesis, Prunus dulcis, radiation use efficiency
Abbreviations: An,C, Daily net photosynthesis of canopy for control trees (mmol m–2 d–1)An,K, Daily net photosynthesis of canopy for kaolin-treated trees (mmol m–2 d–1)E, Photosynthetic radiation use efficiency over one day: net photosynthesis per unit of incident photosynthetically active radiation (mmol mol–1)E50L, Photosynthetic radiation use efficiency calculated with the 50-leaf model the day before kaolin application (mmol mol–1)EHL, Photosynthetic radiation use efficiency calculated with the hypothetical-leaf model the day before kaolin application (mmol mol–1)E50L,R100, Photosynthetic radiation use efficiency calculated with the 50-leaf model the day after kaolin application, using the photosynthetically active radiation incident on leaves as measured by the photosensors (mmol mol–1)E50L,R80, Photosynthetic radiation use efficiency calculated with the 50-leaf model the day after kaolin application, assuming a 20 % reduction in photosynthetically active radiation incident on leaves (mmol mol–1)EHL,R100, Photosynthetic radiation use efficiency calculated with the hypothetical-leaf model the day after kaolin application, using the incident photosynthetically active radiation as obtained from the weather station (mmol mol–1)EHL,R80, Photosynthetic radiation use efficiency calculated with the hypothetical-leaf model after kaolin application, assuming a 20 % reduction in the incident photosynthetically active radiation as obtained from the weather station (mmol mol–1)R, Photosynthetically active radiation (µmol m–2 s–1)Rinc, Daily incident photosynthetically active radiation (mol m–2 d–1)Rtr,C, Fraction of incident photosynthetically active radiation transmitted by the canopy of control trees (no units)Rtr,K, Fraction of incident photosynthetically active radiation transmitted by the canopy of kaolin-treated trees (no units)Rref,C, Fraction of incident photosynthetically active radiation reflected by the canopy of control trees (no units)Rref,K, Fraction of incident photosynthetically active radiation reflected by the canopy of kaolin-treated trees (no units)Rabs,C, Daily photosynthetically active radiation absorbed by the canopy of control trees (mol m–2 d–1)Rabs,K, Daily photosynthetically active radiation absorbed by the canopy of kaolin treated trees (mol m–2 d–1)Sleaf,C, Leaf absorption as fraction of incident photosynthetically active radiation for control leaves (no units)Sleaf,K, Leaf absorption as fraction of incident photosynthetically active radiation for kaolin-treated leaves (no units)
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  D. M. Glenn Particle Film Mechanisms of Action That Reduce the Effect of Environmental Stress in 'Empire' Apple J. Amer. Soc. Hort. Sci., May 1, 2009; 134(3): 314 - 321. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Zvomuya, F. J. Larney, S. M. McGinn, A. F. Olson, and W. D. Willms Surface Albedo and Soil Heat Flux Changes Following Drilling Mud Application to a Semiarid, Mixed-Grass Prairie Soil Sci. Soc. Am. J., September 1, 2008; 72(5): 1217 - 1225. [Abstract] [Full Text] [PDF]
|
|