Pecan, the most valuable nut tree native to North America, is native from northern Illinois and southeastern Iowa to the Gulf Coast of the United States, where it grows abundantly along the Mississippi River, the rivers of central and eastern Oklahoma, and Texas. Popularity and consumer demand for pecans has increased the cultivation of pecan trees to other areas, while commercial production has expanded into many regions of the United States and Mexico.
Effective management of the tree canopy is of vital interest to pecan growers. Pecan trees require careful canopy management to avoid self-shading and to maintain productivity. Leaves of pecan trees typically intercept 65% to 70% of available sunlight with up to 95% light interception in overcrowded, unpruned orchards; less light naturally affects photosynthesis. To improve the amount of light penetration, pecan growers commonly use pruning techniques to increase photosynthesis and flowering on trees. To date, however, little information has been available to growers about the change in photosynthesis activity of pecan leaves throughout the growing season.
Leonardo Lombardini, Hermann Restrepo-Diaz, and Astrid Volder of Texas A&M University's Department of Horticultural Sciences published the results of an experiment using pecan tree cultivars in a recent issue of the Journal of the American Society for Horticultural Science. According to Lombardini and collaborators, the objective of the experiment was to quantify the effects of differences in light intensity on the "morphological characteristics and seasonal physiological performance of sun and shade leaves of field-grown pecan trees".
The experiment was conducted during the 2007 growing season at Texas A&M University. The cultivars used for the research, 'Pawnee' and 'Stuart', were chosen because of their rank as two of the most important pecan varieties for commercial growers.
Treatments were established according to the leaf type (sun or shade leaves) and cultivar. Sun leaves were growing on exterior portions of the tree canopy and were exposed to full sunlight for most of the day (southern exposure). Shade leaves were growing in interior parts of the tree canopy.
The study revealed that pecan shade leaves exposed to saturating radiation are about half as effective as sun leaves in assimilating CO2. Light saturation points were lower for shade leaves and steadily increased as the season progressed for both leaf types. The research showed that late-season photosynthetic capacity was maintained in shade leaves, whereas it was reduced to about 60% in sun leaves.
The authors noted that the results of the research may explain why pecan trees can tolerate severe hedging-type pruning and still maintain high productivity in areas characterized by relatively high light regions (such as the southwestern United States and east-central Australia). The authors explained that "the reduction of canopy size caused by hedging likely increases the ratio of sun-exposed leaves to shaded leaves, thus boosting carbon gain per unit leaf area".
Especially noteworthy is the autumn assimilation drop in sun leaves, without a corresponding assimilation drop in shade leaves, which the authors call "a significant finding".
This study provides baseline information relevant to improving management of the orchard light environment, and can be used by commercial pecan producers for developing new, effective canopy and crop management practices.
The complete study and abstract are available on the ASHS Journal of the American Society for Horticultural Science electronic journal web site: http://journal.ashspublications.org/cgi/content/abstract/134/3/372
Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application.
Michael W. Neff | EurekAlert!
Climate change, population growth may lead to open ocean aquaculture
05.10.2017 | Oregon State University
New machine evaluates soybean at harvest for quality
04.10.2017 | University of Illinois College of Agricultural, Consumer and Environmental Sciences
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
18.10.2017 | Materials Sciences
18.10.2017 | Physics and Astronomy
18.10.2017 | Physics and Astronomy