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  • Author or Editor: H. C. Kohl x
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Abstract

Abscisic acid (ABA) concn as low as 1 ppm, when added to the vase water, effective by reduced water loss of cut roses.

Open Access

Abstract

Seedlings of Petunia hybrida ‘Snow Cloud’ and Pelargonium × hortorum ‘Red Elite’ and ‘Cardinal Orbit’ were grown to anthesis at day air temperatures of 27° ± 3°C (9 hr) and either 7° ± 3° or 18° ± 3° night air temperatures (15 hr). Petunia crop productivity (CP, grams of dry matter produced per square meter of crop) and crop productivity efficiency (CPE, percentage of photosynthetic photon flux incident on the crop stored in the form of crop dry matter) were the same at both temperature regimes from canopy closure to anthesis, but anthesis was delayed 10 days at 7°. Petunias grown at 7° had four more basal branches and were only one-third the height of petunias grown at 18° (12 vs. 37 cm). CP and CPE were 20% lower for geraniums grown at 7° compared to CP and CPE for geraniums grown at 18°. The geraniums grown at 7° flowered 3 weeks later, were more compact, and were 16 to 19 cm shorter than geraniums grown at 18°.

Open Access

Abstract

Seedlings of Petunia hybrida cv. Snow Cloud were subjected to root zone temperatures at the bottom surface of the pots of 15.6° to 19.4°C (NT) or 21° to 35° (HT) and photoperiods of 9 (SD) or 13 hr (LD) for 25 days in a eontrolled-environment chamber with air temperatures of 21° for 9 hr and 15.6° for 15 hr. HT × LD plants produced the largest total leaf area, largest main stem leaves, and most dry weight of all treatments; they were tallest and bloomed first, but had the fewest lateral branches. HT × SD plants developed the most lateral branches at the fastest rate and had a total leaf area, dry weight gain, and root development comparable to those of the LD treatments. NT × SD plants were the smallest. Crop productivity efficiency was determined to be NT × SD = 2.9%, HT × SD = 3.4%, NT × LD = 3.7%, and HT × LD = 3.9%.

Open Access

Abstract

Geranium seedlings (Pelargonium × hortorum L.H. Bailey, ‘Mustang’) grown in 13 hr photoperiods were 23% taller due to stem and petiole elongation, had larger leaves, and prior to canopy closure had a higher crop productivity efficiency (CPE) than seedlings grown under 9 hr photoperiods. In general, the tallest plants were produced when grown with soil temperatures of 18°C. The highest weekly CPE attained was 3.8%.

Open Access

Abstract

Crop productivity efficiencies (CPE) of around 8% (the ratio of the dry weight gain of the crop to the potential to produce dry weight), were realized with petunias (Petunia hybrida Villm.), provided that the crop canopy was essentially closed at the beginning of the 9- to 12-day experimental periods and that there were many branches (sinks). This was found at either long or short photoperiods or at either a normal (15.6°C) or reduced (7.2°) temperature for the 16-hour night periods. Long photoperiods resulted in significantly increased CPE through increased size of the leaves before the crop canopy was closed. Elevated root temperature increased CPE after a sizeable number of lateral branches had formed.

Open Access

A heat-unit model was established for tracking the development of geranium, based on experimental data collected at UC Davis and Rutgers Univ. The temperature thresholds for initiating development and heat-unit benchmarks needed to accomplish each phenostage are parameters in this model. The methods of estimating these parameters were proposed and tested with the observed data. The model worked well during either vegetative or reproductive stages, but failed to predict the initiation of flowers, suggesting that factors other than only temperature drive the flower initiation process. With this model crop development characterized by a series of specific morphological events can be tracked and predicted under various temperature regimes, so that crop timing can be more precise.

Free access

Abstract

Flowers of different cultivars of rose (Rosa hybrida L.) vary in their sensitivity to bent-neck after cutting with ‘Cara Mia’ the most sensitive, and ‘Samantha’ the most resistant of the cultivars tested. Bent-neck is influenced by several factors: water loss by leaves, differences in water uptake ability of the stem, and the ability of the bloom to absorb water from other plant organs on the flower shoot.

Open Access