Premium
An Improved, Rapid, Field Method to Measure Photosynthesis with 14CO2 1
Author(s) -
Naylor D. G.,
Teare I. D.
Publication year - 1975
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1975.00021962006700030031x
Subject(s) - photosynthesis , sorghum , agronomy , volumetric flow rate , ventilation (architecture) , chemistry , biology , botany , physics , meteorology , quantum mechanics
Recognizing a need for a rapid, accurate, one‐man technique for comparing photosynthesis rates in fields, we developed one based on the application of a short pulse of air containing 14 CO 2 over an enclosed leaf (a modification of Shimshi technique) and subsequently determining CO 2 ‐uptake by measuring radioactivity in the enclosed area. The system contains a solenoid on‐off, air‐flow switch driven by an electronic timer, which eliminates human error in judging exposure times, and a miniature photosynthesis chamber designed to ensure adequate ventilation. The 14 CO 2 ‐exposed leaf samples were digested in an organic solubilizer for scintillation counting. Exposure times of 15 to 20 sec produced optimum photosynthetic rates for wheat ( Triticum aestivum L.), soybean ( Glycine max (L.) Merr.), and sorghum ( Sorghum bicolor (L.) Moench); however, optimum gas flow rates varied with crops. Soybean required a higher flow rate for optimum photosynthesis than wheat, sorghum, or corn ( Zea mays ). Photosynthetic rates measured by the 14 CO 2 technique compared well with rates we observed with infrared gas analysis. Sampling time is short and the system is portable and rugged. If consistent exposure time and flow rates are used, the technique can be valuable for comparing photosynthetic rates between genotypes or among various treatments in an experiment.