Developmental and Structural Section
Duarte, David , Ewers, Frank , Bobich, Edward , Bozak, Kristin .
Plastic responses of wood development in California black walnut (Juglans californica): effects of irrigation and post-fire growth.
Plants may respond to varying environmental conditions by altering their internal xylem anatomy as it develops in response to water availability or in their post-fire growth. These changes could impact their ability to transport water or to withstand water stress or other calamities. Juglans califonica S. Watson is one of the dominant trees in Southern California woodlands and is well known for with standing years of severe drought and for resprouting following wildfires. Following a wildfire in one population of this species, unburned adult trees and new growth resprouts were compared. In a second population, irrigated and non-irrigated adults were compared. Plant stems were collected throughout the growing season and vessel diameter, vessel frequency per square mm, transverse vessel lumen area, maximum vessel lengths, and other parameters were measured. There was a significantly greater vessel frequency and vessel lumen area in adults than in resprouts. Both growth forms demonstrated positive increases in percent conductive vessels, percent vessel lumen area, and hydraulic vessel diameter going from February through June,with the addition of the new xylem growth ring. Differences between growth forms in vessel diameter and frequency were correlated to higher mechanical strength (lower vessel frequency and percent vessel lumen area) and greater hydraulic conductivity (greater hydraulic diameter) in resprouts than in adult trees. In the second population, there was a significantly greater vessel frequency and somewhat narrower vessel diameters in irrigated than in non-irrigated trees. Thus, ironically,the irrigated plants had more "xerophytic" xylem traits than non-irrigated plants. Preliminary results indicate maximum vessel length varies some what independently of vessel diameter. Non-irrigated adults had the greatest maximum vessel lengths, about 0.5m on average, whereas resprouts, which had the widest vessels, had the lowest maximum vessel length, about 0.22 m on average. Thus the plastic responses of developing wood may be more complex and interesting than expected. This research may give us a better understanding of how to manage California native woodlands and walnut species worldwide.
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1 - California State Polytechnic University, Pomona, Biological Sciences Department, 3801 West Temple Avenue, Pomona, CA, 91768, USA
2 - California State Polytechnic University, Pomona, Office Of Research, 3801 West Temple Avenue, Pomona, CA, 91768, USA
3 - California State Polytechnic University, Pomona, Biological Sciences, 3801 W. Temple Ave, Pomona, CA, 91768, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union D/Hyatt
Date: Tuesday, July 10th, 2012
Time: 10:30 AM