Root growth and nutrient absorption by dormant plants were studied in root temperature chambers placed in growth rooms so that root and shoot temperatures could be controlled. The roots of dormant Ligustrum ibolium and Euonymus alatus ‘Compactus’ grew at root temperatures of 12.8°C, but were limited at 7.2° and 1.7°. Uptake and translocation of 32P to the dormant shoots were influenced somewhat by root temperature. However, increasing the shoot temperature from 1.7° to 7.2° resulted in a considerable increase in the movement of the isotope to the dormant shoots of both species. Field experiments indicated that nutrients applied in the fall could be absorbed by the plants, contributing to the dormant reserves which could enhance growth the following spring.
Field-grown early forsythia (Forsythia ovata Nakai) plants were harvested every 2 weeks from 15 Apr. through 30 Nov. 1980 and from 15 Aug. to 15 Oct. 1981. Following harvest, plants were divided into roots, shoots formed during previous growing seasons, current season's shoots, and foliage. Plant parts were oven dried, weighed, and analyzed for N, P, and K. Nonlinear regression models of seasonal dry weight and N, P, and K accumulation observed in plants and component parts indicated that maximization of these factors occurred from mid-September to mid-October. Regression analyses indicated statistically significant relationships between observed and estimated dry weights and nutrient element content of each plant part. Harvesting the foliage at the time of peak accumulation of these factors provided the most accurate estimation of dry weight and N, P, and K of maximum seasonal accumulation in whole plants.
Root lengths of an adventitious root system (creeping bentgrass, Agrostis palustris Huds.) and a woody plant fiberous root system (Hetz juniper, Juniperus chinensis L. ‘Hetzii’) were estimated using an automated method employing a video camera and an area/length meter to count scanning line and root intersections. A grid method of root length estimation was used for comparison. Under- and overestimation was random when the automated method was used for creeping bentgrass samples (<80 cm) and the shorter group of juniper root samples (150-550 cm). However, these estimates were much closer to the actual root length, in the ranges evaluated, than the estimates from the grid method. The lengths of long juniper root samples (600-3000 cm) were underestimated consistently with the automated method. The magnitude of this underestimation increased with increasing length. However, the relationship between estimated and actual root length remained linear and was about 76% of the actual length. For the ranges of root length evaluated, this method was found to be useful for root length estimation.