Influence of root zone restriction on mineral element concentration, water potential, chlorophyll concentration, and partitioning of assimilate in spreading euonymus (E. Kiautschovica Loes. ‘Sieboldiana')

Abstract

Euonymus kiautschovica Loes. ‘Sieboldiana’ plants were grown in small‐volume (450 cm³) or large‐volume (13,500 cm³) plastic containers in the greenhouse in a medium containing sandy loam, perlite, and compost and harvested every 4 weeks for 20 weeks. Plants were fertilized with a nutrient solution several times daily to prevent water and nutrient stress. After 8 to 20 weeks, dry weights of leaves on root‐restricted plants (RRP) were less than those of plants grown in large‐volume containers (controls) but the RRP percent dry weights were higher. There were no differences in dry weights of leaves on the main shoot even after 20 weeks of root restriction. Except for weeks 12 and 16, there was no difference in root/shoot ratio. Root restriction had little or no effect on shoot water potential but reduced the concentration of chlorophyll a, b, and total chlorophyll from weeks 8 through 20 by nearly half. Concentrations of N, P, Ca, Mg, and Cu in the leaves of plants grown in small‐volume containers were 23–48% less than those in large‐volume containers; those of A1 and Fe were 52–68% less, and Mo was 50% greater, but there were no differences in concentrations of K, B, Mn, Zn, Na, or Si. Root restriction caused a pronounced shift in dry matter allocation. The relative distribution of assimilate in the lateral shoots of plants grown in large‐volume and small‐volume containers was 59% and 36% respectively, while that in the main shoot was 21% and 46% respectively. This shift in carbon allocation resulted in a marked suppression of lateral bud growth in root‐restricted plants and suggests that root confinement may induce an imbalance in hormone metabolism and/or nutrient uptake.

Notes

Present address: Montgomery College‐Germantown Campus, 20200 Observation Drive, Germantown, MD, 20780

Address for reprint requests: USDA Climate Stress Laboratory, Room 206, B‐001, BARC‐W, Beltsville, MD 20705

Present address: Department of Horticulture, University of Wisconsin, Madison, WI 53706