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Chieri Kubota and Toyoki Kozai

A storage method of transplants in vitro was developed using light compensation points in conjunction with low temperatures. Broccoli (cv. Ryokurei) plantlets, aseptically germinated and cultured for three weeks in vitro, were used as model transplants. Culture conditions were: 23C air temperature, 160 μmol m-2s-1 PPF, and 3.6 air exchanges per hour of the vessel. Prior to storage, light compensation points were determined at 3, 5, 10, and 15C for the plantlets cultured with or without 20 g liter-1 sugar in the medium. Plantlets were stored for six weeks at 5, 10, and 15C under either 0 or 2 μmol m-2s-1 continuous PPF. The light compensation points varied with air temperature and with medium sugar level. Plantlet dry weight during storage was best maintained by keeping CO2 exchange rate of the plantlets close to zero throughout the storage period. High transplant qualities were successfully preserved at light compensation points: 2 μmol m-2s-1 PPF at 5-10C without sugar, and at 5C with sugar in the medium. This method may be applicable for storage of other crop transplants, plug seedlings and cuttings as well.

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Qiansheng Li, Min Deng, Jianjun Chen, and Richard J. Henny

by lowering the light compensation point, thus reducing leaf abscission and maintaining the aesthetic values during interiorscape ( Chen et al., 2005a ; Fonteno and McWilliams, 1978 ; Reyes et al., 1996 ; Yeh and Wang, 2000 ). Production of

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Md. Jahedur Rahman, Haruhisa Inden, and Masaaki Kirimura

hr ; T 2 = twice a day at 0900 hr and 1500 hr ; and T 3 = three times a day at 0700 hr , 0900 hr , and 1500 hr . Vertical bars represent the se of the treatment means. A max , light compensation point, and initial slope of photosynthesis in

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Krishna S. Nemali and Marc W. van Iersel

Physiological acclimation of plants to light has been studied mostly at the leaf level; however whole-plant responses are more relevant in relation to crop growth. To examine the physiological changes associated with different daily light integrals (DLI) during growth of wax begonia (Begonia semperflorens-cultorum Hort.), we grew plants under DLI of 5.3, 9.5, 14.4, and 19.4 mol·m-2·d-1 in a whole-plant gas exchange system. Photosynthesis-light response curves of groups of 12 plants were determined after 25 d of growth. Physiological parameters were estimated per m2 ground area and per m2 leaf area. On a ground area basis, significant increases in dark respiration (Rd), quantum yield (α), the light compensation point (LCP), and maximum gross photosynthesis (Pg,max) were seen with increasing DLI. Variations in physiological parameters among different treatments were small when corrected for differences in leaf area. On a leaf area basis, α, LCP, and the light saturation point (LSP) did not change significantly, whereas significant increases in Rd and Pg,max were seen with increasing DLI. There was a small decrease in leaf chlorophyll concentration (6.3%, measured in SPAD units) with increasing DLI. This study indicates that wax begonias acclimate to low DLI by increasing their leaf chlorophyll concentration, presumably to more efficiently capture the available light, and to high DLI by increasing Pg,max to efficiently utilize the available light, thereby maximizing carbon gain under both situations.

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Terril A. Nell, Ria T. Leonard, and James E. Barrett

Production irradiance levels on growth, light compensation point (LCP), dark respiration (DR), and interior longevity of potted chrysanthemum (Demfranthema grandiflora Tzvelev. cvs. Iridon and Mountain Peak) and poinsettia (Euphorbia pulcherrima Wind. cvs. Annette Hegg Dark Red and Gutbier V-10 Amy) were determined. LCP and DR were measured at anthesis and during acclimatization to interior conditions (10 μmol·s-1·m-2). Days to flowering, inflorescence diameter, total chlorophyll, and interior longevity of chrysanthemum increased when maintained at a mean maximum photosynthetic photon flux density (PPFD) of 500 μmol·s-1·m-2 compared to plants shifted to 300 or 100 μmol·s-1·m-2 8 weeks after planting. LCP and DR were highest at anthesis and were reduced 38% and 49%, respectively, for chrysanthemum and 19% and 42%, respectively, for poinsettia within 3 days in interior conditions. Chrysanthemum plants shifted to 300 μmol·s1·m-2 during production had lower LCP and DR rates at anthesis and throughout time in interior conditions compared to plants maintained at 500 μmol·s-1·m-2. The acclimatization of chrysanthemum to reduced production PPFD is of little significance because interior longevity is reduced. No differences were found in the LCP or DR of poinsettia or chrysanthemum cultivars that differ in interior performance, demonstrating that these physiological characteristics are not good indicators of interior longevity for chrysanthemum and poinsettia.

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Amanda M. Miller, Marc W. van Iersel, and Allan M. Armitage

Light and temperature responses of whole-plant CO2 exchange were determined for two cultivars of Angelonia angustifolia Benth., `AngelMist Purple Stripe' and `AngelMist Deep Plum'. Whole crop net photosynthesis (Pnet) of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were measured at eight temperatures, ranging from 17 to 42 °C. Pnet for both cultivars increased from 17 to ≈20 °C, and then decreased as temperature increased further. Optimal temperatures for Pnet of `AngelMist Purple Stripe' and `AngelMist Deep Plum' were 20.8 and 19.8 °C, respectively. There was no significant difference between the two cultivars, irrespective of temperature. The Q10 (the relative increase with a 10 °C increase in temperature) for Pnet of both cultivars decreased over the entire temperature range. Dark respiration (Rdark) of both cultivars showed a similar linear increase as temperature increased. As photosynthetic photon flux (PPF) increased from 0 to 600 μmol·m-2·s-1, Pnet of both cultivars increased. Light saturation was not yet reached at 600 μmol·m-2·s-1. The light compensation point occurred at 69 μmol·m-2·s-1 for `AngelMist Purple Stripe' and at 89 μmol·m-2·s-1 for `AngelMist Deep Plum'. The lower light saturation point of `AngelMist Purple Stripe' was the result of a higher quantum yield (0.037 mol·mol-1 for `AngelMist Purple Stripe' and 0.026 mol·mol-1 for `AngelMist Deep Plum'). The difference in quantum yield between the two cultivars may explain the faster growth habit of `AngelMist Purple Stripe'.

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Sydney Lykins, Katlynn Scammon, Brian T. Lawrence, and Juan Carlos Melgar

irradiance, and possibly warrant shade or tunnel structures for sun protection of some cultivars over others. Indeed, a comparison of several blackberry cultivars in South America concluded that the light compensation point and net photosynthesis varied

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Domenica Scuderi, Francesco Giuffrida, Stefania Toscano, and Daniela Romano

, which corresponds to the initial slope of the curve at low light levels; and LCP , the light compensation point, which denotes the x-intercept when the net photosynthesis is equal to zero. PPF refers to the incident photosynthetic photon flux. The

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Leonardo Lombardini, Hermann Restrepo-Diaz, and Astrid Volder

locations have dark respiration rate (R d ) values in the range of 0.67 to 1.33 μmol·m −2 ·s −1 of CO 2 , whereas R d in species from the shaded floor of dense forests range from 0.10 to 0.27 μmol·m −2 ·s −1 of CO 2 ( Björkman, 1968 ). Light compensation

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J.M. Sarracino, R. Merritt, and C.K. Chin

Two foliage plant species, Leea coccinia L. and Leea rubra L., exhibited lower light compensation points and faster rates of acclimatization than Ficus benjamina L. when moved from full sun to dense shade, i.e., from 15.7 to 0.26 or 0.09 mol·m·-2day-1. Light compensation points were reduced up to 75% for L. coccinia and 71% for L. rubra after 25 days under these conditions. Uptake of CO2 increased from 65% to 179% and 34% to 118% for L. coccinia and L. rubra, respectively, while respiration rates were reduced from 73% and 76% to 59% to 68%, respectively. Ficus benjamina plants died under similar conditions.