Transpirational Control in C3, C4, and CAM Plants

Project Number:

93R-005

Project Duration:

24 months

Dates:

May 1, 1993 to April 30, 1995

Institution of Principle Investigator while on this project:

University of Arizona

Investigators (most current known information)

Jordan, Kenneth

Professor, Department of Agriculture & Biosystems Engineering, The University of Arizona, 403 Shantz, Building 38, PO Box 210038, Tucson AZ 85721-0038

TEL: +1-520-621-3587, FAX: +1-520-621-3963, Email: kajordan@ag.arizona.edu

Dobrenz, Albert

(Deceased) Formerly: Plant Science Department, The University of Arizona, College of Agriculture, Tucson AZ 85721, USA

Fuchs, Marcel

Agricultural Research Organization of Israel, Institute of Soils and Water, Volcani Center, POB 6, Bet-Dagan 50250, ISRAEL

O'Leary, James

Professor, Office of Arid Lands Studies, The University of Arizona, 1955 East 6th Street, Tucson AZ 85719

TEL: +1-520-621-7154, FAX: +1-520-621-7186, Email: joleary@u.arizona.edu

Proposal Abstract

This study investigated the means of developing experimental verification of models of transpiration and photosynthesis and initiated a series of studies of modeling plant response. A electronic circuit board for analysis of infrared thermograms was purchased and used in two plant studies. A BARD grant, investigating the use of plant temperature in the evaluation of tomatoes grown under shades in the Negev, where experimental infrared data was collected to verify a model of the leaf temperature in the tomato canopy. A finding by CIMMYT researchers that leaf temperature was a useful genetic selection tool in wheat studies led to a preliminary study conducted in Mexico using thermograms. A methodology for comparing plants from different genetic sources was developed but due to some difficulties and changes in personnel insufficient data was collected. An infrared camera with extensive image processing analysis for leaf temperature evaluations is available at the University of Arizona. The study of desert grasses proposed in this grant was not carried to completion for several reasons. The untimely death of Dr. Dobrenz took to the grave the cost-effective procedure of measuring transpiration by transient analysis using IRGA instruments. From other shared sources an ADC LCA₄ transpiration/photosynthesis instrument was obtained. A study of CAM modeling and verification required 3 day continuous measurement over a 6-month period and the desert grass studies were aborted. Investigations on the applicability of using the LCA₄ to measure the CO₂ assimilation versus light intensity with computer-controlled light source. Originally developed by Walker as a stress index measuring the area between the theoretical limits of Blackman's curves and the measured curve. As a stress index it incorporates the photosynthetic mechanisms and thus integrates the many factors which affect productivity.

The original study of C₃, C₄, and CAM metabolism has thus provided seed money and direction for a research focus in Agricultural and Biosystems Engineering that continues to investigate the mechanisms that affect these plants to the present time.