© 2001 Heron Publishing—Victoria, Canada
Soil temperature and plant growth stage influence nitrogen uptake and amino acid concentration of apple during early spring
growth
Shufu Dong (1), Carolyn F. Scagel (2), Lailiang Cheng (3), Leslie H. Fuchigami (1, 5) and Paul T. Rygiewicz (4)
1. Department of Horticulture, Oregon State University, Corvallis, OR 97331, USA / 2. USDA-ARS, Horticultural Crops Research Laboratory, 3420 NW Orchard Street, Corvallis, OR 97330, USA / 3. Department of Fruit and Vegetable Science, 134A Plant Science, Cornell University, Ithaca, NY 14853, USA / 4. U.S. EPA, National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th Street, Corvallis,
OR 97333, USA / 5. Author to whom correspondence should be addressed (fuchigal@bcc.orst.edu) / Received August 22, 2000
Summary
In spring, nitrogen (N) uptake by apple roots begins about 3 weeks after bud break. We used 1-year-old 'Fuji' Malus domestica Borkh on M26 bare-root apple trees to determine whether the onset of N uptake in spring is dependent solely on the growth
stage of the plant or is a function of soil temperature. Five times during early season growth, N uptake and total amino acid
concentration were measured in trees growing at aboveground day/night temperatures of 23/15 °C and belowground temperatures
of 8, 12, 16 or 20 °C. We used 15NH415NO3 to measure total N uptake and rate of uptake and found that both were significantly influenced by both soil temperature and
plant growth stage. Rate of uptake of 15N increased with increasing soil temperature and changed with plant growth stage. Before bud break, 15N was not detected in trees growing in the 8 °C soil treatment, whereas 15N uptake increased with increasing soil temperatures between 12 and 20 °C. Ten days after bud break, 15N was still not detected in trees growing in the 8 °C soil treatment, although total 15N uptake and uptake rate continued to increase with increasing soil temperatures between 12 and 20 °C. Twenty-one days after
bud break, trees in all temperature treatments were able to acquire 15N from the soil, although the amount of uptake increased with increasing soil temperature. Distribution of 15N in trees changed as plants grew. Most of the 15N absorbed by trees before bud break (~5% of 15N supplied per tree) remained in the roots. Forty-six days after bud break, approximately one-third of the 15N absorbed by the trees in the 12–20 °C soil temperature treatments remained in the roots, whereas the shank, stem and new
growth contained about two-thirds of the 15N taken up by the roots. Total amino acid concentration and distribution of amino acids in trees changed with plant growth
stage, but only the amino acid concentration in new growth and roots was affected by soil temperature. We conclude that a
combination of low soil temperature and plant developmental stage influences the ability of apple trees to take up and use
N from the soil in the spring. Thus, early fertilizer application in the spring when soil temperatures are low or when the
aboveground portion of the tree is not actively growing may be ineffective in promoting N uptake.
Keywords:
developmental stage, 15N, Malus domestica, roots..
