Search

In North China, the high-quality pear cultivar “Huangguan” (Pyrus bretschneideri Rehd. cv), which is grafted onto dwarf quince A (Cydonia oblonga Mill. cv) rootstock and grown in calcareous soil, experiences severe iron (Fe) deficiency; this deficiency greatly constrains tree growth as well as fruit yield and quality. Therefore, we evaluated the effects of six practices for alleviating chlorosis caused by Fe deficiency in “Huangguan” grafted onto quince A (HG-QA). The practices included ridging with landscape fabric mulching as a control, flattening with landscape fabric mulching (FM), ridging without landscape fabric mulching (R), flattening without landscape fabric mulching (F), Fe fertilizer application in soil (SFe), foliar Fe application (FFe), and manure application (M). The results showed that the leaf Fe concentration increased by 356% under FFe, compared to that under the control, but the practice failed to alleviate Fe deficiency chlorosis. In contrast, an increase in leaf Fe concentration and chlorosis alleviation were observed under F. F alleviated chlorosis mainly by increasing the root ferric-chelate reductase activity. These results indicate that Fe uptake and utilization in leaves are independent biochemical processes and soil aeration improvement have positive effect on increasing Fe uptake. M improved both the soil active Fe concentration and leaf Fe utilization. Thus, manure application should be the first choice for alleviating Fe deficiency chlorosis in HG-QA grown in calcareous soils. Combining manure application with other practices that increase Fe uptake would likely be an effective way to address the problem of Fe deficiency chlorosis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]