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  • Author or Editor: I.J. Warrington x
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Plants of chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura], radish (Raphanus sativus L.), corn (Zea mays L.), and cucumber (Cucumis sativus L.) were grown under 8-, 12-, 18- or 24-hour daylengths and at three photosynthetic photon fluxes (PPF) within each daylength to evaluate growth and development responses to daily quantum integral (PPF × duration). For the same daily quantum integral, dry matter accumulation and leaf area development were less under 24-hour than under 18-hour daylengths with chrysanthemum and radish. With corn and cucumber, these values were similar under 12-, 18-, and 24-hour daylengths. In all of the species, leaf area and dry matter development were lowest under the 8-hour daylength. Continuous (24-hour) daylength produced some growth abnormalities in radish and chrysanthemum. Specific leaf weight in all species and flower node count in cucumber were linearly related to daily quantum integral up to the highest values examined (73.5 mol·day-1·m-2). All species showed expected photoperiod responses with respect to flowering, but the rate of floral development and number of flower buds formed were highest under the highest PPF (and highest daily quantum integral) treatments. The results indicate that field phenotypes can be obtained in controlled environment (CE) conditions, providing the field daylength and daily quantum integral conditions are reproduced.

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Abstract

‘Red Elite’ hybrid geraniums were grown in controlled environment rooms and greenhouses with 109 combinations of daily light integrals (DLI) ranging from 9 to 25 mol·day−1·m−2 and daily mean temperatures (DMT) from 13.5° to 22.5°C. The time between seedling emergence and macrobud did not change significantly until the DLI was < 13 mol·day−1·m−2 (at 18° DMT). Flowering will not occur below a DLI of 3.3 mol·day−1·m−2. The time between emergence and macrobud progressively decreases as DLI increases until a DLI of close to 13 mol·day−1·m−2 is reached, and with increases in DLI above ≈17 mol·day−1·m−2 there is virtually no increase in the developmental rate of flower buds to the macrobud stage. Rate of development response of ‘Red Elite’ to temperature over the 9° to 27° range was curvilinear. DMT had more influence that DLI between 14 and 25 mol·day−1·m−2 on the time of flower development from macrobud to anthesis. The rate of development response over the 13° to 27° range was linear, and a heat sum relationship could be used to predict flowering. Increased DMT reduced the time between sowing and flowering with consequent reduction in dry weight and flower and bud numbers.

Open Access

Abstract

“Red Elite” geraniums were grown from the 6th leaf stage until the visible bud stage in controlled environment (CE) chambers under 3 day/night temperature regimes (27°/13°, 23°/17°, or 20°/20°C) and under enhanced CO2 (900 μl CO2/liter air) at 27°/13°. Three daily light integral treatments, 24.6, 19.8, and 15.1 mol m−2 d−1, were imposed over each of these 4 treatments. Plants also were grown in a 22714° glasshouse with 2 daily light integral treatments (18.2 or 11.3 mol m−2 d−1). A chlormequat (CCC) drench was applied to half of the plants immediately before the treatments were started. For the period between the 6th leaf and visible bud stages, leaf area, leaf area ratio, specific leaf weight, shoot dry weight, leaf canopy height, and time to visible bud were determined mostly by daily mean temperature rather than by day or night temperature. Most plant growth characteristics, but not the flower bud development rate from 6th leaf to visible bud, were enhanced by supplemental CO2 and suppressed by CCC. After reaching the visible bud stage, plants from some treatments were moved into 24715° CE temperature conditions with or without CO2, whereas others were moved to a glasshouse until harvest at the 1st floret anthesis stage. Between visible bud and anthesis, CCC was the major factor affecting vegetative growth regardless of whether the plants were with or without supplemental CO2 in CE rooms, or in a glasshouse. Anthesis was delayed by about 10 days in the glasshouse compared to the CE treatments but was unaffected by CO2 or CCC treatments. Carbohydrate concentrations were highest (starch 14%, sugar 5%) in plant leaves grown with supplemental CO2 and without CCC, and lowest with no added CO2 but with CCC in all CE treatments. The concentrations were reduced (starch 0.5%, sugar 2.5%) in plant leaves grown in a glasshouse from 6th leaf stage to anthesis because of low daily light integrals and no supplemental CO2.

Open Access

Abstract

Seedlings (72 or 48 days old) of Pelargonium × hortorum cv. Red Elite were grown in 1 experiment from the 6th leaf stage in controlled-environment (CE) rooms at 4 temperatures, including 2 split-night (SN) regimes and at 3 daily-light integrals; in a 2nd experiment they were grown at 2 temperatures including one SN regime, at 3 daily-light integrals, and with and without chlormequat soil drench. Each of the 2 night-temperature periods were of equal duration in the SN regimes. Plants grown under the SN regimes were either similar in growth and reproductive development to plants grown under constant night conditions, where the temperature was the mean of the 2 SN temperatures, or were generally intermediate in growth and development to plants grown throughout the night at each of the 2 temperatures used in the SN regime. A daily mean temperature of 20°C compared to 16.8° or 18° reduced the time between the 6th leaf and macrobud visible stages by 8 days. Leaf starch and sugar levels decreased as mean daily temperatures increased, but increased as daily-light integrals increased. Drenches of (2-chloroethyl)-trimethylammonium chloride (chlormequat) applied at the 6th leaf stage limited plant height and leaf area without influencing flowering date.

Open Access

Abstract

Plants of lettuce (Lactuca sativa L. cv. Grand Rapids), spinach (Spinacia oleracea cv. Bouquet), white mustard (Sinapis alba L.), and wheat (Triticum aestivum L. cv. Karamu) were grown at 2 photosynthetic photon flux densities (PPFD 400 to 700 nm at 320 and 700 μmol s−1m−2 under 4 lamp treatments: metal halide lamps alone, high-pressure sodium lamps alone, metal halide plus tungsten halogen lamps (ca. 1:1 installed wattage), and metal halide plus high-pressure sodium lamps (ca. 1:1 installed wattage). Plants of all species grew well under all treatments and no growth abnormalities were apparent at harvest. It is concluded that dry-weight increase was determined by PPFD and not by spectral irradiance. However, lettuce, spinach, and mustard hypocotyl elongation was greater in young plants grown under the high-pressure sodium lamps in comparison with those grown under the metal halide or metal halide plus tungsten halogen treatments. A strong negative relationship between hypocotyl length and blue photon flux density (400–495 nm) was demonstrated. Anthesis of wheat occurred at the same time under all lamp treatments, but anthesis of mustard differed by 2 days at the higher PPFD and 4 days at the lower PPFD among lamp treatments. The time of anthesis for mustard was found to be weakly but positively correlated with the calculated phytochrome photoequilibrium. Chlorophyll concentrations in young lettuce and spinach plants growing under the high-pressure sodium lamps were 55% and 26% lower, respectively, than those in plants growing under metal halide lamps at the high PPFD level. However, final dry weight was unaffected by any of these morphological differences in the early growth stages.

Open Access

Incremental increases in temperature from 14 to 22 to 30C resulted in linear increases in stem length and node number and decreases in stem diameter and stem strength of Oxypetalum caeruleum (D. Don.) Decne. Higher temperatures also resulted in additional flower abortion, reduced time to flowering, and fewer flowering stems per inflorescence. Reduction in the photosynthetic photon flux (PPF) from 695 to 315 μmol·s-1·m-2 had similar effects as increasing the temperature on vegetative characteristics, but had little effect on reproductive ones. The rate of stem elongation was greatest at low PPF for all temperatures and at high temperature for all PPF treatments. Net photosynthesis rose between 14 and 22C and declined at 30C for all PPF treatments. Long photoperiods (12 or 14 hours) resulted in longer internodes, longer stems, and more flowers per cyme than short photoperiods (8 or 10 hours), but photoperiod had little effect on flowering time. Treatments to reduce latex coagulant and silver thiosulfate treatments had no significant effect on vase life.

Free access

Abstract

Trees of apple cv. Gala (Malus domestica Borkh.), which had previously been dormant pruned, were pruned in mid-December (early summer pruned—73 days after full bloom), mid-January (late summer pruned—108 days after full bloom), or were only dormant pruned (control). On 2 harvest dates (late February and early March) fruit from 4 different regions of the tree canopy were assessed for red blush, background color, soluble solids concentration, and fresh weight. Penetration of photosynthetic photon flux density (PPFD) to each region was measured at the summer pruning times and at the First harvest. Summer pruning increased the percentage of red blush—but not background color—for both pruning dates, decreased fresh weight of fruit from the early pruned trees, and decreased the soluble solids concentration of fruit from the late-pruned trees. The percentage of red blush and fruit fresh weight both showed a highly positive correlation with PPFD penetration, but for fruit fresh weight, the correlation also was dependent on the pruning treatment. The concentration of soluble solids also was related to PPFD penetration although, in comparison with fresh weight, the differences were reduced. Background color was relatively independent of tree position or pruning treatment.

Open Access

A progressive increase in temperature from 14 to 30C resulted in linear increases in stem length and node number and decreases in stem diameter and stem strength. Higher temperatures also resulted in additional flower abortion, reduced time to flowering and fewer flowering stems per inflorescence. Reduction in the photosynthetic photon flux (PPF) from 695 to 315 μmole m-2s-1 had similar effects as increasing the temperature on vegetative parameters but had little effect on reproductive parameters. The rate of stem elongation was greatest at low PPF for all temperatures and at high temperature for all PPF treatments. Net photosynthesis rose between 14 and 22C and declined at 30C for all PPF treatments. Long photoperiods (12, 14 hr.) resulted in longer internodes, longer stems and more flowers per cyme than short photoperiods (8, 10 hr) but photoperiod had little effect on flowering time.

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Container-grown `Delicious', `Golden Delicious', `Braeburn', `Fuji' and `Royal Gala' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] trees, on Malling 9 (M.9) rootstock, were subjected to a range of different maximum/minimum air temperature regimes for up to 80 days after full bloom (DAFB) in controlled environments to investigate the effects of temperature on fruit expansion, final fruit weight, and fruit maturation. Fruit expansion rates were highly responsive to temperature with those at a mean of 20 °C being ≈10 times greater than those at a mean of 6 °C. All cultivars exhibited the same general response although `Braeburn' consistently showed higher expansion rates at all temperatures compared with lowest rates for `Golden Delicious' and intermediate rates for both `Delicious' and `Fuji'. The duration of cell division, assessed indirectly by measuring expansion rate, appeared to be inversely related to mean temperature (i.e., prolonged under cooler conditions). Subsequently, fruit on trees from the coolest controlled temperature treatment showed greater expansion rates when transferred to the field and smaller differences in fruit size at harvest than would have been expected from the measured expansion rates under the cool treatment. Nonetheless, mean fruit weight from warm postbloom treatments was up to four times greater at harvest maturity than that from cool temperature treatments. Postbloom temperature also markedly affected fruit maturation. Fruit from warm postbloom temperature conditions had a higher soluble solids concentration, more yellow background color, lower flesh firmness, and greater starch hydrolysis than fruit from cooler temperatures.

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Apple fruitlet growth responses to temperature were studied, for different durations following bloom (DAFB), under controlled environment (CE) conditions. Container-grown trees of `Red Delicious', `Golden Delicious', `Braeburn', `Fuji', and `Royal Gala' were placed in different maximum/minimum temperature regimes, ranging from 9/3 to 25/15°C for various periods, including 10–40, 10–80, and 40–80 DAFB. Temperature treatments were selected to identify possible differences between mean and maximum/minimum differential effects Trees were placed outdoors following the CE treatment to allow impacts on subsequent fruit development to be determined. The impact of temperature was dramatic. For example, fruit expansion rate for `Red Delicious' varied from 0.12 mm/day at 9/3°C to 0.98 mm/day at 25/15°C. Furthermore, the cell division phase was considerably longer under cooler temperatures. The influence of post-bloom temperature, for even short durations, was evident at harvest in both fruit size and in different fruit maturity indices. Differences in temperature sensitivity were evident amongscultivars. A detailed model has been developed to integrate the responses that have been determined.

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