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The impact of irradiance (0–1200 μmol·m−2·s−1) and carbon dioxide concentration (CO2; 50–1200 ppm) on kale (Brassica oleracea and B. napus pabularia; three cultivars), Swiss chard (chard, Beta vulgaris; four cultivars), and spinach (Spinacea oleracea; three cultivars) photosynthetic rate (P n; per area basis) was determined to facilitate maximizing yield in controlled environment production. Spinach, chard, and kale maximum P n were 23.8, 20.3, and 18.2 μmol CO2·m−2·s−1 fixed, respectively, across varieties (400 ppm CO2). Spinach and kale had the highest and lowest light compensation points [LCPs (73 and 13 μmol·m−2·s−1, respectively)] across varieties. The light saturation points (LSPs) for chard and kale were similar at 884–978 μmol·m−2·s−1, but for spinach, the LSP was higher at 1238 μmol·m−2·s−1. Dark respiration was lowest on kale and highest on spinach (−0.83 and −5.00 μmol CO2·m−2·s−1, respectively). The spinach CO2 compensation point (CCP) was lower (56 ppm) than the chard or kale CCP (64–65 ppm). Among varieties, ‘Red Russian’ kale P n saturated at the lowest CO2 concentration (858 ppm), and ‘Bright Lights’ chard saturated at the highest (1266 ppm; 300 μmol·m−2·s−1). Spinach P n was more responsive to increasing irradiance than to CO2. Kale P n was more responsive to increasing CO2 than to irradiance, and chard P n was equally responsive to increasing CO2 or irradiance. Implications and limitations of this work when “upscaling” to whole-plant responses are discussed.
The prostrate plant habit may be an important new trait for the garden chrysanthemum [Dendranthema ×grandiflora Tzvelv. (=Chrysanthemum ×morifolium Ramatuelle)] market. Fifteen prostrate and non-prostrate genotypes were evaluated in production trials, using Regular and Fast Cropping systems. At flowering, the following traits were evaluated: days to flowering (first, 50%, 100%), flowering duration, pot coverage, plant uniformity, and salability. Salability was measured with consumer evaluations. Genotypes differed significantly for days to first and 100% flowering, flowering duration, plant height, plant width, and plant uniformity. Cropping systems were significantly different for days to first and 100% flowering. `Snowscape', a semi-prostrate day-neutral cultivar, was earlier than all other genotypes for days to first flower. It also had the longest flowering duration. `Snowscape' would be the best genetic source for creating early, continual flowering cultivars. Most prostrate genotypes were as early as commercial cultivars. Genotype 90-275-27 was significantly shorter (prostrate) than all other genotypes and would be the best genetic source for prostrate plants. Genotypes 95-169-8, 92-237-9, 95-157-6, 95-169-10, 90-275-27, and `Snowscape' had the most acceptable plant width for shipping. Plant uniformity of 95-169-10 and 95-169-8 matched that of `Debonair' and `Spotlight', all of which were significantly more uniform than the other genotypes. The least uniform prostrate was 95-331-10. `Snowscape' had the highest (best) index of traits ranking and was significantly better than all other genotypes. Consumer evaluations were highest for non-prostrate cultivars.
The impact of photoperiod, irradiance, and/or cool temperature on flowering and/or dormancy in Mamillopsis senilis and Echinopsis and Trichocereus hybrids was studied. Two- to 3-year-old plants (180 plants of each type) were grown for 4 months under natural daylight (DL) conditions (August–November) in a greenhouse maintained at 26 ± 2 °C. Plants were then placed in either of two greenhouses: a cool temperature house (5 ± 2 °C; DL), or a lighting treatment house (22/18 ± 1 °C day/night temperature, respectively). The lighting treatment house had eight light environments: 1) short day (SD; 8 h; 0800–1600 hr); 2) SD+25–35 μmol·m-2·s-1; 3) SD+45–50 μmol·m-2·s-1; 4) SD+85–95 μmol·m-2·s-1; 5) DL plus night interruption lighting (NI; 2200–0200 hr; 2 μmol·m-2·s-1 from incandescent lamps); 6) DL+25–35 μmol·m-2·s-1 (lighted from 0800–0200 hr); 7) DL+45–50 μmol·m-2·s-1; and 8) DL+85–95 μmol·m-2·s-1. Supplemental lighting was provided using high-pressure sodium lamps. Plants were placed in the cool temperature house for 0, 4, 8 or 12 weeks before being placed under lighting treatments. All plants received lighting treatments for 6 weeks and were then placed in a finishing greenhouse (DL; 22 ± 2 °C). Data were collected on approximate day when growth resumed, the date when each flower opened (five only), total flower number per plant, and how long each flower stayed open (five only). Whether species exhibited dormancy and what conditions, if any, broke that dormancy was identified. Species were also classified into photoperiodic, irradiance, and vernalization response groups with respect to flowering.
A study was conducted to determine if photoperiod, irradiance, and/or a cool temperatures impacted flowering of selected species in five cactus genera. Gymnocalycium, Rebutia, Lobivia, and Sulcorebutia plants were grown for 4 months under natural daylight conditions (August–November) in a greenhouse maintained at 26 ± 2 °C. Plants were then placed in either of two greenhouses: 1) a greenhouse maintained at 22 °C day/18 ± 1 °C night temperature with an 8-h daylength (SD) or natural daylight plus night interruption lighting (NI; 2200–0200 HR), or 2) a greenhouse maintained at 5 ± 2 °C under natural daylight conditions (8–10 h). After 12 weeks at 5 °C, plants were moved to the SD and NI lighting treatments in the before mentioned greenhouse and additional lighting treatment [natural daylight plus supplemental high-pressure sodium lighting (85–95 μmol·m-2·s-1; 0800–0200 HR)]. In all cases, plants were moved out of lighting treatments after 6 weeks and were then grown under natural daylight conditions in a greenhouse maintained at constant 22 ± 1 °C. Data were collected on the approximate date growth commenced, the date when each flower opened (five flowers only), flower number per plant, and individual flower longevity (five flowers only). Species were classified into photoperiodic and irradiance response groups where appropriate and whether species exhibited a vernalization requirement was reported. Lastly, whether dormancy occurred and what conditions overcame that dormancy was reported.
Photoperiod, irradiance, and/or a cool temperature effects on Chamaelobivia hybrid `Rose Quartz' flowering was studied. Two- to 3-year-old plants were grown for 4 months under natural daylight (DL; August–November) in a greenhouse maintained at 26 ± 2 °C. Plants were then placed in either of two greenhouses: a cool temperature house (5 ± 2 °C; natural daylight), or a lighting treatment house (22 °C day/18 ± 1 °C night temperature, respectively). The lighting treatment house had eight light environments: 1) short day (SD; 8 h; 0800–1600 HR); 2) SD+25–35 μmol·m-2·s-1; 3) SD+45-50 μmol·m-2·s-1; 4) SD+85-95 μmol·m-2·s-1; 5) DL plus night interruption lighting (NI; 2200–0200 HR; 2 μmol·m-2·s-1 from incandescent lamps); 6) DL+25-35 μmol·m-2·s-1 (lighted from 0800–0200 HR); 7) DL+45-50 μmol·m-2·s-1; and 8) DL+85-95 μmol·m-2·s-1. Supplemental lighting was provided using high-pressure sodium lamps. Plants were placed in the cool temperature environment for 0, 4, 8, or 12 weeks before being placed under lighting treatments. All plants received a 6-week lighting treatment and were then placed in the finishing greenhouse (22 ± 2 °C). Data were collected on the date when each flower opened (five only), the flower number per plant, and flower longevity (five only). Vernalization interacted with photoperiod to affect flowering. Unvernalized plants exhibited an obligate long-day requirement for flowering. Vernalized plants exhibited a facultative long-day requirement for flowering. The impact of vernalization, photoperiod, and irradiance on flower number, time to flower, and longevity will also be discussed.
Three new Chrysanthemum ×hybrida, garden chrysanthemum cultivars: Red Daisy, White Daisy, and Coral Daisy, are the first in the Mammoth™ series that are advanced interspecific hybrids derived from an open-pollinated cross between hexaploid C. weyrichii (Maxim.) Tzvelv. × C. ×grandiflora Tzvelv. These cultivars are backcross or inbred derivatives of the original interspecific F1 hybrids. All three cultivars are U.S. Department of Agriculture Z3b (−34.4 °C to −37.2 °C) winter-hardy herbaceous perennials exhibiting a shrub habit with the cushion phenotype. Additional traits exhibited by these three cultivars are butterfly attractants, frost tolerance of the flowers, and genetic ‘self-pinching.’ These Mammoth™ cultivars are clonally propagated, virus indexed, protected by U.S. Plant Patents and Canadian Plant Breeder's Rights, and are available from the North American exclusive licensee Ball Seed Company.
Mammoth™ ‘Twilight Pink Daisy’ (U.S. Plant Patent 14,455; Canadian Plant Breeders’ Rights Certificate No. 4192) is an interspecific garden chrysanthemum cultivar, Chrysanthemum ×hybridum Anderson (= Dendranthema ×hybrida Anderson) with common names of hardy mum, chrysanthemum, and garden mum. It is a new and distinct form of shrub-type garden mums in the Mammoth™ series with rosy-pink ray florets, a dark “eye” color in the center of the disc florets, frost-tolerant flower petals, and self-pinching growth. This cultivar is a butterfly attractant in the garden. Mammoth™ ‘Twilight Pink Daisy’ is a winter-hardy herbaceous perennial in USDA Z3b–Z9 (Southeast)/Zone 10 (West) with its cushion growth form displaying extreme hybrid vigor, increasing in plant height from 0.46 m in its first year to a shrub of 0.76 to 1.22 m in the second year and thereafter with greater than 3000 leaves/plant. Flowering is prolific, covering the entire plant at full flowering with as many as greater than 3500 flowers in the second year. Chemical abbreviations: ethanol (EtOH), indole-3-butyric acid (IBA).