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  • Author or Editor: William M. Proebsting x
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Douglas-fir clones have a wide range of rooting potential, but the species is generally considered difficult to root. We have reported previously that NAA is approximately 14-times more active than IBA in the clones tested, with an optimum of about 5 to 10 mM NAA. In contrast, other programs routinely use about 25 mM IBA to propagate Douglas-fir cuttings, a concentration that is relatively inactive in our clones. To address questions raised by these observations, we have incorporated auxin treatments into our long term program to select Douglas-fir clones with high rooting potential. We collect 20 cuttings of each clone identified in Christmas tree plantations, and retain clones rooting ≥ 80%. Beginning in 1991, we treated 10 cuttings of each clone with 5 mM NAA, the other 10 cuttings with 25 mM IBA. Over three years, 1158 clones received the split treatments. Of 222 clones rooting ≥ 80%) approximately half rooted ≥ 80% in response to NAA only. The remainder either responded to IBA or to both NAA and IBA. These results support our previous observations that NAA stimulates rooting of Douglas-fir better than IBA. However, they also suggest that there may be clones sensitive to IBA or to both NAA and IBA.

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Abstract

Cut coastal Douglas-fir trees (1.0 to 1.5 m) were allowed to dry to various water potentials in a greenhouse. About one-half of the tree population, dried to a water potential (ψ) of −3.5 MPa, lost significant quantities of needles but were otherwise comparable to undried trees. Drying to −4.0 MPa or below resulted in significantly reduced water uptake after rehydration and irreversible damage. Changes in percentage of moisture content and stomatal conductance generally paralleled ψ but were less useful indices of the damage threshold. Bark wrinkling and percentage of broken needles were useful morphological indices of the damage threshold. Subjective ratings of quality were less reliable indices of the damage threshold. Water potential was an appropriate single measurement of Christmas tree water status and a suitable index of the damage threshold.

Open Access

Abstract

The abscission zone of Douglas-fir (Pseudotsuga menziesii var. menziesii Mitb. Franco) was studied throughout needle development. A separation layer one cell thick developed at the needle base when extension growth ceased. Cells of this layer stained positively with safranin and slightly with toluidine blue. A protective layer, which developed in stem tissue adjacent to the separation layer, stained positively with safranin, periodic acid-Schiff's reagent, phloroglucinol-HCL and chlorine sulfite. Abscission was induced by drying cut trees to a water potential below −3.5 MPa. Water-stressed trees segregated into abscising and non-abscising needle groups. Walls of separation layer cells from trees with abscising needles were characterized by shrinkage followed by tearing. Walls of separation layer cells from trees with non-abscising needles were anatomically unaffected by water stress. Mechanical damage of cell walls in the separation layer occurred when water stress was −3.5 MPa or lower. Abscission could be prevented by maintaining a water potential above −3.5 MPa.

Open Access

Abstract

Various storage treatments were imposed on cut douglas-fir Christmas trees to measure drying relative to the damage threshold ψ of −3.5 MPa. In a greenhouse (day/night 16°/10° ± 5°C, RH 70-95%), cut douglas-fir dried to −3.5 MPa in 4 days. Overhead irrigation under these conditions maintained ψ about − 3.2 MPa for 9 days. Outdoors (day/night 672° ±9°), ψ declined to a range of −2.5 to −3.0 MPa depending on the weather. Overhead irrigation outdoors maintained ψ between −1.0 to −2.5 MPa. The antitranspirants tested did not reduce the rate of water loss significantly in the greenhouse. Outdoors, ψ of Vapor Gard-treated trees was similar to the irrigated trees, but Vapor Gard caused serious cosmetic defects. None of the other antitranspirants tested reduced moisture loss outdoors.

Open Access

Abstract

Needle starch metabolism was studied during graft development of Colorado blue spruce (Picea pungens Englemann ‘Hoopsi’) scions on Norway spruce [Picea abies (L.) Karst] rootstocks. Starch accumulated during the initial stages of union formation, but the rate of accumulation slowed over time. Peak starch content in developing greenhouse grafts was ≈30% and, in lath house grafts, ≈50% of that in 3-year-old grafts forced in the greenhouse. Prior to budbreak, starch content declined rapidly, stabilizing at pre-grafting levels during shoot elongation. Grafts with misaligned unions accumulated starch during the first week, but the starch content then declined. Preventing photosynthesis in scions during union formation prevented starch accumulation, but did not affect graft success or subsequent scion growth. We concluded that neither starch accumulation nor current photosynthesis in the scion were required during union development.

Open Access

Abstract

The study evaluated the roles of storage carbohydrates and neutral lipids in the success of Colorado blue spruce (Picea pungens Englemann ‘Hoopsi’) grafts. These scions do not require photosynthesis nor receive photosynthates from the rootstock during union development. Carbohydrate and neutral lipid contents, along with respiration and scion water relations, were measured during union development. Stored carbon compounds were sufficient to supply the needs of the scion during the 9 weeks of union development. Estimates of carbohydrate use indicated that decreases in sugar content (bark and needle) were insufficient to account for more than 25% of the estimated respiration. The results indicate that the quantity of carbon storage compounds is not a factor in graft success. We propose that neutral lipids may be the major carbon reserve of the scion during graft formation.

Open Access

Abstract

Several techniques were tested to improve the development of Colorado blue spruce (Picea pungens Engelm. ‘Hoopsi’) grafts. In the Pacific Northwest, Picea grafts are normally made on active rootstocks in heated greenhouses between December and mid-March. Grafting on dormant rootstocks and holding these grafts in an unheated, polyethylene-covered lath house resulted in generally higher graft success. IBA, NAA, and BA applied to the base of the scion just before grafting increased graft success by 10% to 13%. Retarding the development of the rootstock by dikegulac applications or by bud removal stimulated scion growth. Polyethylene tents and a film-forming anti-transpirant had no effect on graft success. Chemical names used N-(phenylmethyl)-1H-purin-6-amine (BA); 2,3:4,6-bis-0-(l-methylethylidone)-a-l-xylo-2-hexulofuranosonic acid (dikegulac); 1H-indole-3-butyric acid (IBA); 1-naphthaleneacetic acid (NAA).

Open Access

Propagation of Corylus avellana stem cuttings may be limited by either root initiation or bud abscission. We divided juvenile shoots of 3 varieties growing in layering beds in mid-July into 4 or 5 3-node cuttings with leaves at the upper two nodes, except that terminal cuttings had one expanded leaf. Cuttings were treated with 5 mM IBA in 50% EtOH, a mixture of A. rhizogenes strains A7 + 22 or left untreated. IBA and bacteria stimulated rooting of cuttings from all shoot positions. Rooting of the terminal cuttings (<50%) was less than that of the sub-terminal cuttings (>80%). Bud retention was <50% on terminal cuttings, nearly 100% on sub-terminal cuttings. Using juvenile stock plants of various varieties, sub-terminal cuttings treated with Agrobacterium or 5 mM IBA may yield 70-90% cuttings with both roots and buds, Agravitropic roots, characteristic of genetic transformation, were observed on Agrobacterium-treated cuttings. Dot blots probed for TL-DNA were negative, however.

Free access

Propagation of Corylus avellana stem cuttings may be limited by either root initiation or bud abscission. We divided juvenile shoots of 3 varieties growing in layering beds in mid-July into 4 or 5 3-node cuttings with leaves at the upper two nodes, except that terminal cuttings had one expanded leaf. Cuttings were treated with 5 mM IBA in 50% EtOH, a mixture of A. rhizogenes strains A7 + 22 or left untreated. IBA and bacteria stimulated rooting of cuttings from all shoot positions. Rooting of the terminal cuttings (<50%) was less than that of the sub-terminal cuttings (>80%). Bud retention was <50% on terminal cuttings, nearly 100% on sub-terminal cuttings. Using juvenile stock plants of various varieties, sub-terminal cuttings treated with Agrobacterium or 5 mM IBA may yield 70-90% cuttings with both roots and buds, Agravitropic roots, characteristic of genetic transformation, were observed on Agrobacterium-treated cuttings. Dot blots probed for TL-DNA were negative, however.

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Hazelnut (Corylus avellana L.) softwood cuttings of the cultivars Ennis and Casina were propagated under mist during June and July 1987 and 1988. Rooting of stem cuttings was stimulated by both Agrobacterium and IBA treatment; however, IBA caused nearly complete bud abscission. Better rooting and bud retention were observed in `Casina' than in `Ennis' in 1988. Bud retention on Agrobacterium -inoculated cuttings improved as the cuttings approached the semi-hardwood stage. Six months after transplanting, Agrobacterium -inoculated hazelnut cuttings had an extensive root system, characteristic of hairy root. Although the mechanism remains unclear, strains of Agrobacterium rhizogenes are effective rooting agents in hazelnut and may cause less bud abscission than IBA. Chemical name used: 1 H -indole-3-butyric acid (IBA).

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