ABSTRACrExamination of the relationship betwee photosnthesis an growth of a do I white oak (Quevcw alm L) tree hs shown that most greow processes were eer led or well aderway before the ests t of s t posve rates of net potosts Growth was intiated first In the root system (March 3), folowed by stem cambial grwth (March 26) and later by flower, kleaf an b grwth (April 10 The photosynthetic process of white oak has been investigated in several studies (3,9,14 in clay content with depth from a silty clay loam at 30 cm to a clay at 67 cm. The soil was fully hydrated at the beginning of this study.PLANT MATERIAL The study tree was a 19-m-tall white oak (59 years old) with a diameter of 33.5 cm at 1.3 m. Branches and leaves utilized in this study were restricted to the upper one-fourth of the crown to facilitate attachment of the cuvette and to reduce mutual shading.An earlier study with '4CO2 had shown within the crown of the study white oak tree that there was no statistical difference in photosynthetic potential between the bottom and the top of the crown (3). On each sampling date, a branch having three to five leaves was selected for study. The branch was arbitrarily selected to obtain a set of leaves which reflected the average leaf development observed for the upper portion of the crown on each sampling date. In addition, on 2 days (April 30 and May 1), expanding green shoots with leaves removed were selected for study. Shoots which provided the maximum amount of new tissue available to be enclosed in the cuvette were selected since the Ph.of this tissue was expected to be low.Descrition of Measurement SystemL Net photosynthetic rate of leaf and stem tissue was determined with an open system composed of a ventilated thermoelectric cuvette and Beckman (model 315) IRGA differential CO2 analyzer. CO2 concentrations of the supply gas to the cuvette were monitored with a Beckman (model 215) absolute analyzer. Water vapor was removed before entering both IRGAs with a condensor. Changes in water vapor concentration between the supply and the gas from the cuvette were determined with a dew point hygrometer (EGG model 880), and were used to estimate transpiration. A thermoelectric plate in the base of the cuvette provided the ability to vary leaf temperature from near 0 to 45 C (±1.5 C).

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Two year old shoots of Salix fragilis L. were treated with morphactin and Ethrel to observe the influence of these compounds on xylem differentiation. Three treatments were used: I) morphactin IT 3456 was applied on 23 May 1976; 2) Ethrel on 23 May 1976; and 3) Ethrel on 20 June 1976. Each compound was applied in a lanolin paste as a ring around the shoot. The samples were collected at the end of the growjng season. Each treatment caused a pronounced swelling around the place of treatment. Both wood and bark were markedly influenced by the treatments. Anatomical analyses of xylem revealed: 1) a disorientation of cell types in all samples, 2) the formation of tyloses in all samples (with nucleated bud-type in the latter Ethrel treatment), 3) a general lack of vessels in the morphactin treatment, 4) the occurrence of crystals in longitudinal elements and highly lignified fibres immediately following both Ethrel treatments, and 5) the occurrence of areas of low birefringence immediately following the latter Ethrel treatment. These observations indicate the influence that these treatments have on xylem differentiation, primarily through an interference with endogenous hormones.

A study was conducted to determine if exogenously applied indole-3-acetic acid would stimulate symmetric or asymmetric compression wood formation in stems of rooted cuttings of Pseudotsuga menziesii (Mirb.) Franco. Dormant two-year-old rooted cuttings were decapitated one cm below the terminal bud and treated with IAA in lanolin emulsion. Plants treated with IAA at 1 or 10 mg/g concentrations produced up to 25 rows of new xylem cells during the three week treatment period, while control plants produced essentially none. Compression wood formation was greater on the upper (originally adaxial) than on the lower side of the stem. The results support the hypothesis that basal curvature of rooted Douglas-fir cuttings is the result of a system developing a transverse gradient in auxin content in the stem leading to asymmetric compression wood formation.

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