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Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/19/2006 Publication Date: 10/3/2006 Citation: Fleisher, D.H., Timlin, D.J., Reddy, V. 2006. Temperature influence on potato leaf and branch distribution and canopy photosynthetic rate. Agronomy Journal. 98:1442-1452. Interpretive Summary: Crop growth models are used to predict plant responses to factors including light, temperature, nutrients and water. Scientists and farmers can use these predictions to help make decisions such as when to irrigate or add fertilizer. Most potato models use a simple approach to simulate the growth and development of leaves and stems. However, the accuracy of these models can be improved by adding more detail on potato canopy growth. Experiments were conducted on the appearance and distribution of leaves and branches in the potato canopy at different air temperatures. The contribution of these leaves to plant photosynthetic rate was also evaluated. The results indicate that estimating the correct amount of leaf area at different depths of the potato canopy is important. This information will be used to improve an existing potato crop model. Farmers, scientists, and policy planners who need improved predictions on potato responses to nutrient, water, climate, and land-use changes will benefit from the research. Technical Abstract: Mature potato (Solanum tuberosum cv. Kennebec) canopies are composed of leaves originating from main stem and axillary stem branches. Canopy leaf distribution and corresponding contribution to whole canopy photosynthetic rates has not been quantified. An experiment using six Soil-Plant-Atmospheric Research (SPAR) chambers maintained at 16 hour day / night thermoperiods of 14/10, 17/12, 20/15, 23/18, 28/23 and 34/29 degrees C was conducted. Canopies were divided into three horizontal layers of equal depth once main stem leaves ceased expansion (between 50 and 64 days after emergence). The canopy was defoliated at each layer, from the ground upwards, on successive days, allowing the photosynthetic contribution from different layers to be measured. Leaf area followed a quadratic relationship with temperature for the entire canopy and within each canopy layer, with highest areas occurring between 16.6 and 22.1 degrees C. Main stem leaves accounted for more than 50 percent of total leaf area at 22 degrees C and below. Canopy maximum photosynthetic rates, AMAX, prior to harvest were similar for all treatments (27.3 to 34.1 umol CO2/square meter/s) except 34/29 degrees C. AMAX and canopy light utilization efficiency declined in all treatments as successive canopy layers were removed, primarily due to decreases in light interception in the canopy. These results indicate that the relative proportion of main or axillary stem leaves are not as important for potato modeling considerations as is the need to simulate the correct quantity of leaf area. |
