Abstract
The remobilization of storage nitrogen (N) is affected by growth characteristics of young pear trees. Aboveground parts of young pear trees grafted on P. betulifolia grew more vigorously than that on dwarfing rootstocks. Therefore, the remobilization of storage N within young pear trees on vigorous rootstocks may be different from that on dwarfing rootstocks. A 15N tracing experiment, including six groups of one-year-old pear trees grafted on vigorous rootstocks in 2016, was conducted to investigate the mobilization of storage N from 2016 to 2018. Results indicated that about 44%, 31.4% and 24.6% of storage N remobilized in new growth was derived from the trunk, shoots and roots, respectively. Most of storage N remobilized in new organs were supplied by trunks and shoots. About 82.2% of storage N withdrawn from senescent leaves were recovered in the trunk and shoots during autumn. The aboveground parts played a more important role than roots in the cycling process of storage N in young pear trees. However, as compared with young pear trees on dwarfing rootstocks, more storage N recovered in new organs were supplied by roots of that on vigorous rootstocks, due to vigorous growth and more nutrient requirement of aboveground parts.
Highlights
The remobilization of stored nitrogen (N) is a key factor influencing N uptake, growth, development, and longevity of deciduous fruit trees [1,2,3,4]
The aboveground of young pear trees grafted on the vigorous rootstocks grew more vigorously than that on the dwarfing rootstocks
More than 25% of the N taken up in former years within a whole young pear tree was remobilized in the leaves, which was far higher than that in the shoots and fruits
Summary
The remobilization of stored nitrogen (N) is a key factor influencing N uptake, growth, development, and longevity of deciduous fruit trees [1,2,3,4]. The low soil temperatures result in minimal low activity in root systems, and the N to sustain new organ growth is mainly remobilized from the perennial tissues [9,12,13,14,15]. Studies on apple [16,17], walnut [18] and persimmon trees [19] show that approximately half of the total tree N amount is remobilized to sustain new organ growth. Similar results were concluded by the studies on the sycamore [22], nectarine [6], apple [23], walnut [24], persimmon [19], cherry [25,26] and peach trees [27]. The studies on the apple [28], pear [10] and walnut trees [29]
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