ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
PHOTOSYNTHESIS AND GROWTH OF CAROLINA BUCKTHORN (RHAMNUS CAROLINIANA) DURING DROUGHT AND FLOODING: COMPARISONS TO THE INVASIVE COMMON BUCKTHORN (RHAMNUS CATHARTICA) |
| Authors: | J.R. Stewart, W.R. Graves |
| Keywords: | water stress, nursery crops, stress physiology |
| Abstract:
Common buckthorn (Rhamnus cathartica L.) is a stress-resistant but undesirable Eurasian shrub naturalized in North America. We are examining whether one of its more attractive North American relatives, Carolina buckthorn (Rhamnus caroliniana Walt.), merits increased use in managed landscapes prone to variable and extreme soil-moisture conditions. We first characterized photosynthesis and growth of Carolina buckthorns subjected to five soil-moisture treatments that ranged from complete inundation of the root zone to severe drought and then compared potted seedlings of Carolina buckthorn to those of common buckthorn for their responses to partial flooding and drought under greenhouse conditions. Multiple irrigation cycles were imposed; each was terminated when soil-moisture content had decreased to 10 percent or less. The first experiment showed maximal photosynthetic rate of Carolina buckthorn occurred near 30% soil moisture, and that death of Carolina buckthorns can result from root-zone inundation. We then found that mean net photosynthesis of Carolina buckthorn exceeded that of common buckthorn by approximately 30 percent over soil-moisture contents of from 1 to 60 percent. Carolina buckthorn resisted marked deleterious effects of partial flooding. In contrast, common buckthorn showed leaf epinasty and reduced rates of photosynthesis rapidly upon initial exposure to partial flooding, but long-term exposure led to recovery of photosynthesis and normal shoot development. We conclude that both species are capable of maintaining carbon fixation and growth over a wide range of soil-moisture contents but common buckthorn appears to undergo morphological, anatomical, or physiological adjustments in extremely wet soil to optimize its growth and net photosynthesis. | |
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