TITLE:
Scaling Leaf Measurements to Estimate Whole Canopy Gas Exchanges of Cotton
AUTHORS:
Dennis C. Gitz III, Jeffrey T. Baker, Robert J. Lascano
KEYWORDS:
Cotton, Gossypium hirsutum, Scaling, Assimilation, Transpiration, Drought Stress
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.7 No.14,
October
11,
2016
ABSTRACT: Diurnal leaf and canopy gas exchanges of
well-watered field grown cotton were measured. Our objective was to scale
leaf-level values of transpiration and net assimilation to the whole canopy
level using estimates of canopy leaf area. Single leaf gas exchange
measurements were made with two portable photosynthesis systems and canopy measurements
with four open Canopy Evapo-Transpiration and Assimilation (CETA) chamber
systems. Canopy leaf area was measured at the end of the experiment and estimated
during gas exchange by fitting values to a growth curve. Leaf level measurements
were arithmetically scaled to estimate canopy level gas exchange based on canopy
leaf area and then compared to the measured values. Scaled values of single
leaf transpiration were very similar to canopy transpiration measurements,
although both whole canopy transpiration and assimilation were overestimated
around mid-day. We conclude that canopy cotton transpiration of well-watered
field grown plants could be estimated within 5% throughout the day by scaling
leaf level measurements to the whole canopy using measured canopy leaf area.
Estimating canopy assimilation from leaf level measurements remains
problematic.