© 1998 Heron Publishing—Victoria, Canada
Responses of citrus fine roots to localized soil drying: a comparison of seedlings with adult fruiting trees
Javier F. Espeleta (1, 3) and David M. Eissenstat (2, 4)
1. Citrus Research and Education Center, University of Florida, Institute of Food and Agricultural Sciences, Lake Alfred, FL
33850-2299, USA / 2. Department of Horticulture, The Pennsylvania State University, University Park, PA 16802-4200, USA / 3. Department of Botany, University of Georgia, Athens, GA 30602-7271, USA / 4. Author to whom correspondence should be addressed (dme9@psu.edu) / Received January 10, 1997
Summary
We studied the responses of citrus (Citrus volkameriana Tan. & Pasq.) roots to 15 weeks of soil drying. A comparison was made between the fine roots of 1-year-old seedling root
systems (seedling) and the fine roots of woody laterals of 6-year-old grafted trees (adult). Each seedling and woody lateral
root system was established in a pair of vertically separated and independently irrigated soil compartments located in field
root chambers excavated adjacent to the trees to which the woody laterals were attached. Root + soil respiration and fine
root survival of seedlings and adults were similar for the first 5 weeks. However, eight weeks after termination of irrigation
to the upper soil compartments, mortality of fine roots was high in adults but not seedlings. Fine roots of adults exposed
to dry soil for 5, 8 and 15 weeks exhibited 2, 26 and 33% mortality, respectively, whereas the corresponding values for fine
roots of seedlings were 2, 6 and 8%. Although root + soil respiration rates of adults and seedlings were similar before the
soil drying treatment, rates for adults were only 25% of those for seedlings after 15 weeks of soil drying. We conclude that,
although fine roots of adults and seedlings are similar in form, they respond differently to soil drying.
Keywords:
Citrus volkameriana, drought, fine roots, root death, root respiration, Rutaceae, tree juvenility, Volkamer lemon.
