Translocation pathways in the petioles and stem between source and sink leaves of Populus deltoides Bartr. ex Marsh.

Microautoradiography was used to follow the translocation pathways of ¹⁴C-labeled photosynthate from mature source leaves, through the stem, to immature sink leaves three nodes above. Translocation occurred in specific bundles of the midveins and petioles of both the source and sink leaves and in the interjacent internodes. When each of six major veins in the lamina of an exporting leaf was independently spot-fed ¹⁴CO₂, label was exported through specific bundles in the petiole associated with that vein. When the whole lamina of a mature source leaf was fed ¹⁴CO₂, export occurred through all bundles of the lamina, but acropetal export in the stem was confined to bundles serving certain immature sink leaves. Cross-transfer occurred within the stem via phloem bridges. Leaves approaching maturity translocated photosynthate bidirectionally in adjacent subsidiary bundles of the petiole. That is, petiolar bundles serving the lamina apex were exporting unlabeled photosynthate while those serving the lamina base were simultaneously importing labeled photosynthate. The petioles and midveins of maturing leaves were strong sinks for photosynthate, which was diverted from the export front to differentiating structural tissues. The data support the idea of bidirectional transport in adjacent bundles of the petiole and possibly in adjacent sieve tubes within an individual bundle.Abbreviations C central leaf trace - L left leaf trace - LPI leaf plastochron index - R right leaf trace     

Isolation of selective 3H-chlornaltrexamine-bound complexes,possible opioid receptor components in brains of mice

The nonequilibrium narcotic antagonist, chlornaltrexamine (CNA) was used to bind selectively and covalently pioid specific sites on brain membrane preparations. Selective binding of [³H]CNA occured with a saturation maximum of 185 fmol/mg protein. Bound [³H]CNA was extracted with Triton X-100, dialyzed against Brij 36T, precipitated with trichloroacetic acid and chromatographed on an ultrogel AcA 22 column. The elution profile suggests that this extract contains a minimum of four selective [³H]CNA complexes. At least two of these complexes migrate in a single large peak. Column calibration showed that this peak eluted at 590,000 daltons. One of these specific [³H]CNA complexes elutes at the elution volume of the column and is dialyzable. Finally, putative aggregate of these complexes elutes with the void volume.     

Purification, characterization, and quantitation of the antigen employed in the immunodiffusion test for diagnosis of equine infectious anemia.

Equine infectious anemia (EIA) antigen extracted from the spleen of horses infected with EIA virus was purified by pH treatment, (NH4)2SO4 fractionation and affinity chromatography. The homogeneity of the antigen was indicated by sedimentation rate and sedimentation equilibrium experiments. A S20,w of 0.51 was determined and a molecular weight of 7600 was calculated from sedimentation equilibrium analysis. The amino acid composition of the pure antigen indicated the antigen is an acidic protein. Employing radical immunodiffusion (RID) and pure antigen a method for quantitating antigen content of antigen containing preparations was developed.     

DEVELOPMENT AND ORGANIZATION OF THE SECONDARY VESSEL SYSTEM IN POPULUS GRANDIDENTATA

The apical 22 cm of a dormant, first-year sprout of Populus grandidentata was sectioned serially, and the primary and secondary xylem systems were studied microscopically and graphically reconstructed. A total of 15 nodes was present on the mature stem and 14 foliar primordia in the dormant bud. The vascular traces in the lower portion of the mature stem conformed to a 2/5 phyllotaxy while those of the upper portion and within the dormant bud conformed to a 3/8 phyllotaxy. The 2/5 to 3/8 phyllotactic transition occurred in an extremely precise and systematic two-step pattern: (1) The lateral traces shifted to a new point of origin on the parent central trace, and (2) three new central traces were initiated in sequence by divergences from left-traces. Metaxylem, when followed downward, conformed to the arrangement of the procambial trace system only within one orthostichy. Below this point, the metaxylem components of lateral traces physically separated from those of the protoxylem and continued downward on a new course. Metaxylem vessels produced by the trace cambium originated from a postulated vessel-generating center at the stem-petiole junction. Each metaxylem vessel developing basipetally through the primary body was continuous with a secondary vessel developing basipetally in the secondary body. Because secondary development closed the vascular cylinder, vessels originating from developing leaves or primordia situated at higher levels in the shoot were displaced radially outward when they entered the secondary xyelm. The distribution of vessels in the secondary xylem can therefore be accounted for by a knowledge of the production and distribution of metaxylem vessels in the primary body.     

Incorporation of C-photosynthate into major chemical fractions of source and sink leaves of cottonwood

The incorporation and distribution of photosynthetically fixed ¹⁴CO₂ was followed for 48 hours in a recently matured source leaf (LPI 7) and in young expanding source and sink leaves (LPI 4) of cottonwood (Populus deltoides Bartr.). The major chemical constituents of leaf laminae and petioles were separated by sequential solvent extractions and enzyme hydrolyses. Two hours after labeling, about 80% of the ¹⁴C was found in water-alcohol-soluble constituents in the mature source lamina as compared to about 45% in those of the young expanding leaf. In both mature and expanding source leaves the water-alcohol-soluble constituents decreased while the CHCl₃-soluble and -insoluble compounds increased with time. After 48 hours, 7 and 37% of the total ¹⁴C was recovered from structural carbohydrates and from protein + CHCl₃-soluble fractions, respectively, in the mature source leaf; and 4 and 65%, respectively, in the young source leaf. When the distribution of ¹⁴C among major chemical fractions was calculated on per cent dpm/mg basis, the data showed that a young sink leaf incorporated over twice as much ¹⁴C into structural carbohydrates as a young source leaf (11% versus 4%). However, when calculated on an absolute dpm/mg basis, activity in this fraction of the young source leaf exceeded that in the sink leaf by a ratio of about 11:1 (9528 versus 845 dpm/mg). Thus, most of the material for synthesis of structural carbohydrates was derived from in situ photosynthate.     

Correlations between net auxin and secondary xylem development in young Populus deltoides

Stems of cottonwood ( Populs deltoides Bartr. ex Marsh.) plants grown under different conditions were examined to determine the relation between net endogenous auxin yields and the acropetal advance of the primary-secondary vascular transition zone (TZ). In all treatments, the internode yielding maximum net auxin activity, as determined by the Avena curvature bioassay, closely corresponded with the internode in which the TZ occurred. Under short-day (SD) dormancy-inducing conditions, auxin yield declined steadily while the maximum auxin peak and the TZ shifted toward younger internodes. Auxin yields from these plants were extremely low after 5 weeks of SD compared with those from long-day (LD) plants. The only consistent auxin yield was obtained from internodes subtending young leaves beneath the apical bud. Plants placed in SD for 3 weeks and then returned to LD conditions showed an immediate increase in auxin yield in the stem, and the progressive acropetal advance of the TZ under SD was reversed. Therefore, within 7 LD the positions of the TZ and peak auxin yield corresponded to those observed before the imposition of SD Fully dormant plants placed in LD showed a dramatic rise in auxin yields during the first 2 weeks of renewed growth. Although low levels of auxin were found in the newly developing shoots after 6 LD, yields increased rapidly after 9 and 14 LD. The position of the TZ corresponded with the peak of net auxin activity after 9 and 14 LD.