Arboriculture & Urban Forestry 34(1): January 2008 Arboriculture & Urban Forestry 2008. 34(1):29–40. 29 The Influence of Nitrogen Fertilization on Waterlogging Stresses in Fagus sylvatica L. and Quercus robur L. Glynn C. Percival and Ian P. Keary Abstract. The aims of this study were to determine the influence of nitrogen (N) fertilizers on tree tolerance under prolonged waterlogging conditions and investigate the effect of N fertilization on aiding tree recovery from waterlogging damage using containerized English oak (waterlogging-intermediate) and European beech (waterlogging-sensitive) as test species. English oak proved to be more waterlogging-tolerant than European beech. Tree vitality as measured by chlorophyll fluorescence, photosyn- thetic rates, leaf chlorophyll content, stomatal conductance, leaf and root protein concentration, and foliar N content was consis- tently higher in trees in which N fertilizers were added to the waterlogged solutions compared with trees waterlogged with tapwater only for 18 days. Measurement of light absorbance, light trapping, electron transport, and dissipation fluxes per leaf cross-section of photosystem II after the 18-day waterlogging period indicated a beneficial influence of N fertilization on leaf photosynthetic processes at the cessation of the waterlogging period. Addition of N induced greater resource allocation in favor of roots over shoots in both tree species. At the cessation of the 18-day waterlogging period and after a 10-day regeneration period, growth (leaf area, shoot, root, total plant dry weight) was constantly higher in N waterlogged trees compared with non-N waterlogged ones. In a separate study, recovery rates of trees as measured by chlorophyll fluorescence, photosynthetic rates, leaf chlorophyll content, and stomatal conductance over a 6-week period after the cessation of 18 days waterlogging were 30% to 50% higher in N-fertilized trees compared with non-N-fertilized trees irrespective of species. In all cases, nonfertilized trees had the least capacity for recovery. In addition, leaf area, shoot, root, and total plant dry weight were higher in N-fertilized trees compared with nonfertilized ones. Results of this investigation indicate 1) applications of N fertilizers enhance the tolerance of trees under prolonged waterlogged conditions; and 2) applications of N fertilizers after waterlogging stress would be of benefit to improve tree recovery rates and growth. From a practical point of view, N fertilization 14.5 g (0.51 oz) or greater N per liter (0.26 gal) of water is tentatively suggested based on preliminary results of this study. Key Words. Chlorophylls; chlorophyll fluorescence; English oak; European beech; photosynthesis; physiogenic stress; plant health care; protein; root deoxygenation; stress enzymes, stress tolerance. Soil deoxygenation as a result of excess water application, im- peded drainage, mechanical compaction, or impermeable surface coverings is an almost ubiquitous factor in the urban landscape (Percival and Hitchmough 1995). In waterlogged soils, air spaces become filled with water delaying the diffusion of gases among the atmosphere, rhizophere, and roots (Hitchmough 1994). Dissolved oxygen is further depleted from the soil solu- tion by respiration of roots and soil microorganisms. Depletion of dissolved oxygen in waterlogged soils can occur in several hours leading to hypoxia (deficiency in oxygen reaching the tissues) or anoxia depending on soil temperature, respiration activity of the plant, and the frequency and duration of soil saturation. Once oxygen concentrations fall below 15% within soil pores, root functioning is impaired affecting numerous physiological and metabolic processes (Kozlowski et al. 1991; Crook 1992). These include disintegration of leaf ultra structure leading to wilting, chlorosis, abscission, and reduced photosyn- thetic capacity as well as stem hypertrophy, blackening of roots, and death (Percival 2004). Cytological investigations conducted in woody plant roots indicated water stress damages the cellular membranes of root tips. At different development stages, the occurrence of damage such as lack of protoplasm, formation of membrane vesicles, and coagulation of cytoplasmic content has been demonstrated (Chiatante et al. 2000). At the whole plant level, symptoms include yellowing leaves, particu- larly between the veins, soft tissue at the leaf base, wilting, shoot dieback, physical deterioration of the root system that visibly appears blue–black in color, and peeling bark (Mclean 1993). Applications of nitrogen (N) fertilizers have been shown to modify plant responses to waterlogging in a range of economi- cally important agricultural crops. Pezeshki et al. (2000) con- cluded that the growth of planting stocks for wetland mitigation could be improved by N fertilization in the nursery. Work by Huang et al. (1994a) showed increasing plant nutrient supply improved shoot nitrogen status of wheat genotypes that contrib- uted to superior growth of waterlogged plants compared with nonfertilized controls. Application of calcium nitrate to the sur- face of waterlogged soils prevented the onset of waterlogging damage as manifest by leaf chlorosis, reduced leaf chlorophyll concentration, and dry weight in barley cultivars (Drew et al. 1979), whereas Hodgson and MacLeod (1987) concluded foliar- applied N could be used to reduce the effect of prolonged wa- terlogging in cotton. Although most studies conclude that N fertilizer application can alleviate some of the adverse effects of prolonged waterlogging in terms of tolerance and survival, this research has been conducted primarily with crop rather than woody ornamentals. The tactical use of N fertilizers as an ameliorant against wa- terlogging damage and recovery from waterlogging stresses in woody plants has received little investigation. The aims of this investigation were to: ©2008 International Society of Arboriculture
January 2008
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
