Growth analysis of spreading euonymus subjected to root restriction

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Abstract
A comparative growth analysis was made of spreading euonymus (E. kiautschovica Loes. ‘Sieboldiana') plants grown in the greenhouse for 20 weeks in 0.45 L (small) or 13.5 L (large) plastic pots of Beltsville sandy loam soil [amended with composted cow manure: perlite (2:1 v/v)]. In general, plants in small vs. large pots showed a decrease in specific leaf area (SLA), leaf area ratio (LAR), and mean relative growth rate (MRGR); an increase in specific leaf mass (SLM) and leaf mass ratio (LMR); but no difference in net assimilation rate (NAR). There was an increase in SLA and LAR and a decrease in SLM and LMR from weeks 0 to 4 in both sizes of pots and an increase in NAR in small pots, from the first to the second 4‐week interval, possibly reflecting a recovery from transplanting shock. There were no differences in NAR between small and large pots during the 20‐week period. The MRGR was 23% less in small pots than in large pots during the first 4‐week interval, and 27% less during the third 4‐week interval, but otherwise showed no difference. From weeks 4 to 20, SLA and LAR declined 50% and 64% in small pots and 28% and 54% in large pots, while SLM increased 106% and 37%, respectively, in small and large pots. Since NAR was approximately constant with respect to pot size, reduced LAR was the major factor responsible for decrease in dry matter accumulation in small pots. These findings indicate the important role of leaf expansion as a determinant of plant growth during root restriction.