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  • Author or Editor: R. G. Anderson x
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Abstract

Resistance to the twospotted spider mite (Tetranychus urticae Koch) of 18 cultivars of ivy geranium [Pelargonium peltatum (L.) L’Her ex Ait.] was evaluated under greenhouse conditions by mass screening, by measuring fecundity on isolated leaves, and by paired leaf tests for selected cultivars. ‘Sybil Holmes’, ‘Yale’, and ‘Cornell’ were among the most susceptible, whereas ‘Double Lilac White’, ‘Sunset’, and ‘Salmon Queen’ were relatively mite-free. ‘Madeline Crozy’ and ‘Cornell’ were preferred for oviposition over the resistant ‘Double Lilac White’. Mite resistance was not related to density of simple or glandular leaf trichomes, but there was an apparent relationship between mite susceptibility and severity of oedema.

Open Access

Abstract

Continuous high intensity supplementary lighting from October to March with a combination of Lucalox and Multivapor lamps at 116W/m2 reduced the number of days to root vegetative cuttings of chrysanthemum, geranium and poinsettia and increased root number, length, and fresh weight over non-lighted cuttings. Lighting benefits were lost at 174W/m2 when foliar chlorosis developed and delayed rooting and reduced root growth. Leaf temperature of misted cuttings receiving 116W/m2 and 174W/m2 of supplementary light on sunny December days were 2.7° and 5.1°C, respectively, higher than non-lighted leaves.

Open Access

A series of experiments were conducted to determine the sensitivity of radish to four light alcohols (ethanol, methanol, 2-propanol, and t-butanol) identified as atmospheric contaminants on manned spacecraft. Radish (Raphanus sativus L. `Cherry Bomb' Hybrid II) seedlings were exposed for 5 days to concentrations of 0, 50, 100, 175, 250, and 500 ppm of each alcohol and the effect on seedling growth was used to establish preliminary threshold response values. Results show a general response-pattern for the four alcohol exposures at threshold responses of 10% (T10), 50% (T50) and 90% (T90) reduction in seedling length. There were differences in the response of seedlings to the four alcohols, with the T10 for t-butanol and ethanol (25 to 40 ppm) being 3 to 5× lower than for methanol or 2-propanol (110 to 120 ppm). Ethanol and t-butanol exhibited similar T50 values (150 to 160 ppm). In contrast, T50 for methanol (285 ppm) and 2-propanol (260 ppm) were about 100 ppm higher than for ethanol or t-butanol. Chronic exposures to 400 ppm t-butanol, ethanol or 2-propanol were highly toxic to the plants. Radish was more tolerant of methanol, with T90 of 465 ppm. Seeds did not germinate at the 500 ppm treatment of t-butanol, 2-propanol, or ethanol. There were significant differences in projected performance of plants in different environments, dependent upon the regulatory guidelines used. The use of exposure guidelines for humans is not applicable to plant systems.

Free access

Abstract

The rhizomes of 3 cultivars of tall bearded irises (Iris spp.)—‘Cayenne Capers’, ‘Babbling Brook’, and ‘Stepping Out’—were stored at 2°C for 9, 14, and 18 weeks and then forced to anthesis in a greenhouse. During vernalization, rhizomes were either planted into pots or placed on cooler shelves. Rhizomes of ‘Cayenne Capers’ required no vernalization to develop the flower bud, yet vernalization was required for ‘Babbling Brook’ and ‘Stepping Out’. The longer the vernalization period, the shorter the time to flower after being removed to the forcing environment. Rhizomes not planted during vernalization required more time to flower than those which were planted.

Open Access

Abstract

Mature ‘Red Delicious’ apple trees (Malus pumila Mill) were sprinkled intermittently with an overhead irrigation system after completion of winter rest. A 2-minute sprinkling cycle operated automatically whenever the ambient air temperature of the orchard exceeded 7°C until the control trees reached full bloom. Evaporative cooling of the treated trees reduced bud temperatures to within 2°C of the wet bulb temperature. Treated trees reached full bloom 17 days after the untreated controls.

Open Access