Search Results

Abstract

Global radiation on cloudless days within apple trees varied considerably. At most times on any day absorption of global radiation was dependant on solar zenith angle and was greatest between 1 and 2m from the tree tops. Measurements of penetrating global radiation were similar whether made on E-W or N-W tracks and differed little in trees on M.26 and M.7 except deep in the canopy where energy levels were lower in the latter.

Attenuation of infra-red radiation was less than visible resulting in higher levels of infra-red relative to visible deep in the canopy.

Apples from trees on M.7 had less red color than those on M.26 but the amount of red color formed was positively correlated with global radiation. At the same global radiation fruit color was better on M.26 than on M.7. This may, in part, be a rootstock or tree training effect. An estimated minimum energy of 250 cal cm^-2 day^-1 was necessary for the initiation and maintenance of red color in apples.

A series of six experiments was conducted over eight years to investigate impacts of provenance on transplant establishment in landscapes and the role of adventitious root regeneration in differential genotypic responses during establishment of Platanus occidentalis L. Fall, spring, and summer transplants of container-grown half-sib families (HSF = seedlings derived from a single mother tree with unknown male parentage), including two selections native to Brazos County, Texas (Brazos-C, Brazos-D), one native to Cookeville, Tenn. (Cookeville), two Kentucky/Tennessee HSF from the Westvaco Corp. (WV-10, WV-14), and two Texas HSF from the Texas Forest Service tree improvement program (TFS-09, TFS-24), were established to determine field/landscape growth responses. Subsequent studies were conducted to investigate differential leaf gas exchange responses of TFS-09 and Cookeville during moderate water deficits and to determine root regeneration potential (RRP) responses of TFS-09, Brazos-C, WV-14, and Cookeville HSF following fall, spring, and summer transplant. To investigate consistency of within-family genotypic responses and to determine relationships among adventitious root initiation from shoot cuttings, RRP, and landscape establishment, five seedlings of TFS-09 and five from Cookeville HSF were clonally propagated and ramets tested under field and RRP conditions similar to those with seedling-derived plants. Regionally native HSF consistently grew taller, had larger trunk diameters, and often had greater survival during the first 3 years in the landscape than HSF not native to the region in which the studies were conducted. Rapidity of root regeneration among HFS at the time of transplant was the best root growth related predictor of successful landscape establishment. Some growth advantages were found using genetically improved HSF, but not as consistent an improvement as with the use of seedlings from regional provenances. Within-family variation in landscape performance was greater with nonregional Cookeville clones than with regional TFS-09 clones, however there was overlap among the more vigorous Cookeville clones and the least vigorous TFS-09 clones. Increased rapidity of root regeneration and drought adaptations related to leaf morphology and gas exchange characteristics may be involved in enhanced growth responses of Texas regional genotypes. No consistent relationships were found among adventitious rooting responses from shoot cuttings and subsequent RRP of the same genotypes from root tissues or their growth during the first 3 years in landscapes.