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The cutleaf hazelnut [Corylus avellana L. f. heterophylla (Loud.) Rehder] is grown as an ornamental for its distinct leaf shape. Its leaves are slightly smaller, more deeply lobed, and more sharply toothed than those of standard hazelnut cultivars. When the cutleaf hazelnut was crossed with cultivars with normal leaves, all seedlings had normal leaves. When seedlings were backcrossed to their cutleaf parent, half of the seedlings expressed the cutleaf trait, and when crossed with each other in pairs, 25% of the seedlings were cutleaf. These segregation ratios indicate that the cutleaf trait is conferred by a single recessive gene for which the symbol cf is proposed. Progenies segregating simultaneously for leaf shape and color indicate that the cutleaf locus is independent of the locus controlling red leaf color and of the locus controlling a chlorophyll deficiency, which appears to be identical to that previously observed in seedlings of `Barcelona'.

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The cutleaf hazelnut [Corylus avellana L. f. heterophylla (Loud.) Rehder] is an ornamental form with strongly dissected leaf morphology. Its stigmas express incompatibility allele S20 but none of the other 25 S-alleles was detected with fluorescence microscopy. Three seedlings from a cross of the cutleaf hazelnut and VR6-28 lacked S20 and were investigated further. Each expressed an allele from the parent VR6-28 (S2 S26), S26 in OSU 562.031 and OSU 562.048 and S2 in OSU 562.049. S2 and S26 are low in the dominance hierarchy, so we expected the new allele from the cutleaf hazelnut to be expressed in their pollen. Unexpectedly, fluorescence microscopy showed that pollen of all three selections was compatible on their cutleaf parent and on each other, and furthermore, self-pollinations showed the excellent germination and long parallel tubes in the styles that are typical of a compatible pollination. Controlled self- and cross-pollinations in the field verified the self-compatibility of two selections. Cluster set for self-pollinations was very high (75-90%) and within the range observed for compatible cross-pollinations. Furthermore, the frequency of blank nuts was low (<10%). The second allele in the cutleaf hazelnut is designated S28, and its presence in seedlings of `Cutleaf' is indicated by the absence of S20. Controlled pollinations in the field also showed that selection OSU 562.069 (S2 S28) from the cross `Cutleaf' × `Redleaf #3' was self-compatible. Fluorescence microscopy showed that two additional seedlings were self-incompatible [OSU 367.052 (S1 S28) and OSU 367.076 (S6 S28)] while a third [OSU 706.071 (S9 S28)] was self-compatible. Self-compatibility may be limited to genotypes that combine S28 with a second allele that is low in the dominance hierarchy.

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Two studies were conducted to determine if selected grass and dicot species had an allelopathic interaction with pecan (Carya illinoinensis Wangenh. C. Koch). Leachate from pots with established grasses or dicots was used to irrigate container-grown pecan trees. Leachates from bermudagrass [Cynodon dactylon (L.) Pers.], tall fescue (Festuca arundinacea Shreb. cv. Kentucky 31), redroot pigweed (Amaranthus retroflexus L.), and cutleaf evening primrose (Oenothera laciniata Hill) reduced leaf area and leaf dry weight about 20% compared to the controls. Bermudagrass, tall fescue, and primrose leachate decreased pecan root weight 17%, trunk weight 22%, and total tree dry weight 19% compared to the control. In a second study, trees were 10% shorter than the control when irrigated with bermudagrass or pigweed leachate.

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Growth of `Apache' pecan [Carya illinoinensis (Wangenh.) K. Koch] seedlings was evaluated for 3 years when grown in a 11.2-m2 weed-free area or when various combinations of one or two plants of cutleaf evening primrose (Oenothera laciniata Hill), a cool-season species, or Palmer amaranth (Amaranthus palmeri S. Wats.), a warm-season species, were grown 30 cm from the tree, with the rest of the 11.2-m2 area weed-free. Either weed species alone suppressed tree growth compared to the weed-free control. A temporal succession of primrose followed by amaranth reduced growth most. After 3 years, two plants of primrose followed in succession by two of amaranth caused a 79% reduction in cumulative current-season's growth.

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Burgundy Lace is a new ornamental hazelnut ( Corylus avellana ) cultivar. It was released by the Oregon Agricultural Experiment Station in Apr. 2015. ‘Burgundy Lace’ combines the deeply dissected leaves of the cutleaf hazelnut with red leaf color

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initial applications, smooth crabgrass was 8 to 15 cm tall, cutleaf groundcherry was 5 to 8 cm tall, and spiny amaranth was 5 to 8 cm tall. Smooth crabgrass represented 60% of the weed cover, whereas cutleaf groundcherry and spiny amaranth represented 36

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applications. At the time of initial applications, smooth crabgrass was 8 to 10 cm tall, cutleaf groundcherry was 5 cm tall, spiny amaranth was 8 to 10 cm tall, and yellow nutsedge was 10 to 15 cm tall. Smooth crabgrass represented 60% of the weed cover, while

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; cutleaf eveningprimrose and swinecress, with cutleaf eveningprimrose being the more common species each year of the study. Solarization during the preceding summer did not affect either of the cool-season weeds present in these trials (data not shown

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Abstract

The growth of cutleaf crabapple [Malus toringoides (Rehd.) Hughes] seedlings was greatly accelerated by direct seeding under CO2-enriched atmospheres (400 or 2000 ppm) in controlled-environment chambers. CO2 treatment of 2000 ppm for 4 weeks from the time of seeding in the growth chamber produced the most striking results in terms of increase in node number and stem length. By the end of 4 weeks of treatment, stem lengths of seedlings treated for 4 weeks in the growth chamber with 2000 ppm CO2 were 3 times greater than those of plants grown at ambient CO2 (ca 350 ppm) in the greenhouse for 4 weeks, and 1.5 times greater than those treated in the growth chamber with 400 ppm CO2 for 4 weeks. The effect of CO2 enrichment on stem length was greater than that on node number. The stimulatory effects of CO2 enrichment persisted for 2-3 months after the plants were moved to the greenhouse at ambient CO2.

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separated using Fisher’s protected least significant difference test ( P < 0.05). Results and discussion Cutleaf eveningprimrose ( Oenothera laciniata ), lesser swinecress ( Coronopus didymus ), and henbit ( Lamium amplexicaule ) were the predominant weeds

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