Growth of young apple trees in relation to reserve nitrogen and carbohydrates

Tree Physiol. 2002 Dec;22(18):1297-303. doi: 10.1093/treephys/22.18.1297.

Abstract

Bench-grafted Fuji/M.26 apple (Malus domestica Borkh.) trees were fertilized with a nutrient solution (fertigation) containing 0, 2.5, 5, 7.5, 10, 15 or 20 mM nitrogen (N) in a modified Hoagland's solution from June 30 to September 1. In mid-October, half of the trees in each N treatment were sprayed twice with 3% urea, 1 week apart. The remaining trees served as controls. All trees were harvested after leaf fall and stored at 2 degrees C over winter. One group of trees from each treatment was destructively sampled before bud break to determine amounts of reserve N and total nonstructural carbohydrates (TNC); the remaining trees were transplanted to N-free medium in the spring. These trees were supplied with Hoagland's solution with or without 10 mM N (from 15N-depleted NH4NO3) for 60 days, starting from bud break. With increasing N supply from fertigation, tree N concentration increased, whereas TNC concentration decreased. Foliar urea applications increased tree N concentration and decreased TNC concentration in each N fertigation treatment. There was a negative linear relationship between tree N concentration and TNC concentration. Irrespective of whether N was provided the following spring, trees with high N reserves but low carbohydrate reserves produced a larger total leaf area at the end of the regrowth period than trees with low N reserves but high carbohydrate reserves. The pooled data on reserve N used for new growth showed that, regardless of the spring N supply, there was a linear relationship between total N accumulated in the tree during the previous season and the amount of reserve N remobilized for new shoot and leaf growth. About 50% of tree N content was remobilized to support new shoot and leaf growth over the range of tree N status examined. We conclude that the initial growth of young apple trees in the spring is determined mainly by reserve N, not reserve carbohydrates. The amount of reserve N remobilized for new growth in spring was proportional to tree N status and was unaffected by current N supply.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomass
  • Carbohydrates / analysis
  • Carbohydrates / physiology*
  • Malus / chemistry
  • Malus / growth & development*
  • Malus / physiology
  • Nitrogen / analysis
  • Nitrogen / physiology*
  • Plant Leaves / chemistry
  • Plant Leaves / growth & development
  • Plant Shoots / chemistry
  • Plant Shoots / growth & development
  • Trees / chemistry
  • Trees / growth & development*
  • Trees / physiology

Substances

  • Carbohydrates
  • Nitrogen