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  • Author or Editor: Christian Wien x
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Simple unheated greenhouses covered with clear polyethylene, also known as high tunnels, in which plants are typically grown in the ground have become popular for extending the growing season for high-value horticultural crops. Although they are used principally to produce annual crops such as vegetables and cut flowers, increasing interest has focused on their use for perennial crops such as raspberries, blackberries, and ornamentals. Studies of temperature variation within the tunnel during the growing season have emphasized the rapid rise in air day temperature above ambient during the day and an equally rapid decrease at night. Spatial variation in temperature within the tunnel were much less marked, however, with air temperatures at the edge of a 10-m wide tunnel only ≈2 °C lower than in the center. For perennial crops, tunnel conditions during the off-season are also an important factor. In winter, air temperatures in the tunnel during sunny days rose above freezing even when ambient air temperatures stayed below freezing. Soil temperatures during the day and night fluctuated much less both inside and outside the tunnel and were significantly higher in the tunnel. Studies with nursery plants overwintered in similar structures indicate that spatial variation is again dwarfed by the overall air temperature fluctuation in these structures.

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The petals of some sunflower (Helianthus annuus) cultivars used as cut flowers are easily knocked off the flower; this ruins its appearance and destroys its market value. The objectives of this study were to characterize an abscission zone, if present, at the base of petals of sunflower florets in cultivars that differ with respect to petal drop and to determine if differences in the nature and/or development of the abscission zone among cultivars were correlated with differences in timing with respect to petal drop. In the first experiment, we measured the force required to pull petals from the flower head; in the second we investigated changes in the anatomy of the petal–achene juncture. Anatomical analysis revealed a differentiated region (the abscission zone) at the junction of the petal and achene consisting of cells with a different morphology from those above and below it. Cell division at the abscission zone of the short-lived cultivar occurred earlier than in the long-lived cultivar. These differences indicate that whereas the anatomical nature of the abscission zone is similar in the two cultivars, Procut Yellow Lite (PYL) and Procut Bicolor (PBC), the tempo of development differed. Specifically, the abscission layer reached full differentiation, or maturity, sooner in PBC, hence its earlier petal drop, than in PYL.

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In a two-year field experiment, sweet corn was intercropped with a perennial cover of white clover. The clover was suppressed after corn emergence by rototilling. The nitrogen exchange between the corn, clover, and soil was closely monitored. Soil sampling indicated the rate and amounts of mineralization of nitrogen from soil organic matter and clover. Fertilizer labelled with 15-N was used to assess contributions of nitrogen from the various sources.

Results from 1989 showed little nitrogen benefit to the corn from the clover. Content of 15-N in the corn indicated that non-fertilizer nitrogen uptake was similar in monocropped and intercropped corn treatments. Corn yields were correlated with the amount of nitrogen fertilizer applied.

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In a two-year field experiment, sweet corn was intercropped with a perennial cover of white clover. The clover was suppressed after corn emergence by rototilling. The nitrogen exchange between the corn, clover, and soil was closely monitored. Soil sampling indicated the rate and amounts of mineralization of nitrogen from soil organic matter and clover. Fertilizer labelled with 15-N was used to assess contributions of nitrogen from the various sources.

Results from 1989 showed little nitrogen benefit to the corn from the clover. Content of 15-N in the corn indicated that non-fertilizer nitrogen uptake was similar in monocropped and intercropped corn treatments. Corn yields were correlated with the amount of nitrogen fertilizer applied.

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When grown in containers, pineapple lily (Eucomis sp.) can produce excessively long foliage and tall scapes, particularly in cultivars with tall pineapple lily (Eucomis comosa) parentage. Height control, through the use of plant growth regulators (PGRs), is necessary to improve crop quality of potted pineapple lily. In year 1 of these trials, bulbs of cultivars Reuben, Tugela Jade, and Tugela Gem were given substrate drenches of flurprimidol or paclobutrazol, each at 2, 4, or 6 mg per 6-inch pot. Drenches were applied at the “visible inflorescence” stage. As concentration increased, scapes were generally shorter in all cultivars for both PGRs, but there was no effect on foliage length or production time. At the rates tested, the reduction in scape length was insufficient to produce marketable plants of the three cultivars. In the second year, substrate drenches were applied at an earlier stage than in year 1, at “leaf whorl emergence,” when shoots were about 7 cm tall. The PGR treatments were notably more effective at controlling plant height in the second year. As concentration increased, scape and foliage length was reduced relative to the controls in all three cultivars for both PGRs. For all cultivars, inflorescence leaning and toppling were sharply reduced at all application rates compared with untreated controls. The reduction in plant height observed in year 2, particularly in plants treated with 4 or 6 mg/pot, resulted in plants with compact scapes and foliage proportional with their 6-inch containers.

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The objective of this study was to determine effects of bulb size on production time and factors influencing crop quality in pineapple lily (Eucomis sp.) cultivars developed originally for cut flower production. The percentage of bulbs producing an inflorescence increased as bulb size increased. One hundred percent of bulbs >18 cm circumference flowered in three of the four cultivars whereas ‘Tugela Jade’ exhibited 88% flowering. The number of flowers per inflorescence increased as bulb size increased. Scape length increased as bulb size increased in ‘Reuben’. Inflorescence length increased as bulb size increased in ‘Reuben’, ‘Tugela Jade’, and ‘Tugela Gem’. Days to anthesis from planting decreased as bulb size increased in ‘Reuben’ and ‘Tugela Jade’. For all cultivars, the largest bulbs produced the greatest number of leaves per plant and the highest quality inflorescences, largely attributable to the larger number of flowers produced per inflorescence compared with smaller bulbs.

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In the floriculture trade, cut pepper (Capsicum annuum) stems are typically grown for their fruit to add color contrast to the foliage and blossoms of conventional floral arrangements. Stems are commonly stripped of foliage because leaves wilt rapidly. Three divergent plant types and commercial hydration protection spray products were evaluated to identify effective vase life treatments and new pepper lines that combine both fruit and foliar interest with an acceptable postharvest cut stem life. Three inbred US Department of Agriculture pepper breeding lines with a tall vigorous growth habit and black foliage were selected for evaluation as cut stems. Line 190-2 produced upright, tabasco-like fruit; 191-1 produced upright, clustered, round fruit; and 196-1 was fruitless. Three commercial spray treatments Crowning Glory (FLCG), Finishing Touch, and Aqua Finish Clear (AFC) were evaluated on treated cut stems stored at 10 and 23 °C. The pepper breeding line had the greatest influence on cut stem foliage and fruit vase life. The fruitless line, 196-1 exhibited an extended vase life in comparison with fruited lines. Cold storage extended the vase life of cut stems. FLCG reduced foliage vase life at 23 °C, and AFC extended foliage vase life of the fruitless line 196-1. Relative to foliage, fruit exhibited greater resistance to desiccation, with glossier fruit of 191-1 desiccating more rapidly than fruit of 190-2. Similar trends were noted when cut stems were stored at 10 °C for 7 days and moved to 23 °C. However, in 2022 trials, the vase life of 190-2 was shortened, and those of 191-1 and 196-1 were extended, highlighting the influence of preharvest factors on vase life. The results demonstrate that cut stems of new pepper lines with vigorous upright growth habits and black-pigmented foliage, together with diverse fruit morphology, provide innovative possibilities for stunning cut flower arrangements.

Open Access

Abstract

Tomatoes (Lycopersicon esculentum Mill.) were sampled for laboratory analysis of nitrate nitrogen (NO3-N) in one greenhouse and four field experiments. A ratio of about 3:1 (petiole NO3-N to whole leaf NO3-N) was found over a wide range of conditions for the third leaf below the growing tip and leaves further below this point. The ratio was higher for the very youngest leaves. Nitrate-N increased with leaf age and then remained relatively constant. Whole leaves proved just as effective as petioles for reflecting changes in available N.

Open Access