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Title: Impact of Applied Nitrogen Concentration on Growth of Elatior Begonia and New Guinea Impatiens, and Susceptibility of Begonia to Botrytis cinerea

Author
item PITCHAY, DHARMALINGAM - RAKERS'S GREENHOUSE
item Frantz, Jonathan
item Locke, James
item Krause, Charles
item FERNANDEZ, GEORGE - UNIVERSITY OF NEVADA

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2006
Publication Date: 2/1/2007
Citation: Pitchay, D., Frantz, J., Locke, J.C., Krause, C.R., Fernandez, G. 2007. Impact of Applied Nitrogen Concentration on Growth of Elatior Begonia and New Guinea Impatiens, and Susceptibility of Begonia to Botrytis cinerea. Journal of the American Society for Horticultural Science. 132:193-201.

Interpretive Summary: Plant performance and appearance over wide ranges of nutrients are well characterized. However, less is known about the potential subtleties of plant growth, form, development, nutrient uptake, and biotic stress tolerance in the broad tolerable range. Begonia and New Guinea impatiens were grown over a wide range of nitrogen (N) in a peat: perlite soilless substrate in greenhouse conditions. Plant growth, development, chlorophyll content, leaf angle, nutrient uptake, tissue caloric value, and susceptibility to grey mold disease were evaluated in two experiments. Elevated N supply resulted in decreased plant height, flower numbers, bud numbers, canopy area, and mass. Chlorophyll content saturated at an N supply of about 200 ppm. N uptake efficiency, shoot N use efficiency, and shoot N utilization efficiency decreased with increasing N supply. Elevated levels of N supply from 100 ppm to 800 ppm also increased the susceptibility of Beg to grey mold by 10% to 80% in stems and 3% to 14% in leaves. The increase in susceptibility also corresponded with increased tissue energy content (kJ g-1) and altered leaf orientation. This study indicates many plant changes occur between nutrient extremes that can have a significant impact on growth, development, and the ability to withstand disease.

Technical Abstract: Plant performance and appearance in deficient and toxic levels of nutrients are well characterized. However, less is known about the potential subtleties of plant growth, form, development, nutrient uptake, and biotic stress tolerance in the broad tolerable range. Begonia (Beg, Begonia × tuberhybrida Voss) and new guinea impatiens (NGI, Impatiens hawkeri Bull.) were grown over a wide range of N (from 1.78mM to 57.1 mM NH4:NO3 ratio at a 1:1 ratio supplied as nutrient solution) in a peat: perlite soilless substrate in greenhouse conditions. Plant growth, development, chlorophyll content, leaf angle, nutrient uptake, tissue caloric value, and susceptibility to Botrytis cinerea Pers.:Fr. disease were evaluated in two experiments. Elevated N supply resulted in decreased plant height (16% in Beg and 7% to 16% in NGI), flower count (3% to 48% in Beg and 7% to 49% in NGI), bud numbers (23% to 80% in Beg), canopy area (11% to 33% in NGI) and mass (21% to 33% in Beg and 18% to 58% in NGI). Chlorophyll content saturated at an N supply of 28.6 mM. N uptake efficiency, shoot N use efficiency, and shoot N utilization efficiency decreased with increasing N supply. Elevated levels of N supply from 7.15 mM to 57.1 mM also increased the susceptibility of Beg to B. cinerea disease by 10% to 80% in stems and 3% to 14% in leaves. The increase in susceptibility also corresponded with increased tissue energy content (kJ g-1) and altered leaf orientation. This study indicates many plant changes occur between nutrient extremes that can have a significant impact on growth, development, and the ability to withstand disease.