Daily light integral influences rooting and quality of petunia cuttings
Daily light integral influences rooting and quality of petunia cuttings
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每日光照积分影响矮牵牛插条的生根和质量
DOI：
10.17660/actahortic.2006.711.51
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
E. Runkle
中科院分区：
文献类型：
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作者：
R. Lopez;E. Runkle
在无根草本扦插繁殖过程中，为了减少温度和水分胁迫，通常会降低光照强度，但对于营养繁殖的重要园艺一年生植物，光照量对生根和扦插生长的影响尚未量化。在日光照积分（DLI）为1.2 ~ 3.9 mol·m·d的条件下，矮牵牛（Petunia Tiny Tunia ' Violet Ice '， ×hybrida）扦插繁殖。DLI环境使用无遮荫或30%，55%和70%编织遮荫布创建。所有的岩屑都被放置在有雾的温室中，温度保持在25℃，蒸汽压差为0.3 kPa。12小时的光周期使用9小时的自然日，由软白色荧光灯延长。扦插后8、12、16 d分别进行生根和生长评价。随着栽培条件的增加，扦插生根率和扦插质量均有所提高。例如，繁殖16 d后，DLI从1.2 mol·m·d增加到3.9 mol·m·d，使扦插枝长度从6.3 cm减少到4.1 cm，使平均根数从17根增加到36根，使最长根的平均长度从9.4 cm增加到12.9 cm。随着DLI的增加，繁殖16 d后收获的插枝根和地上部干重分别增加了452%和47%。因此，在繁殖过程中应妥善管理DLI，以减少生根时间，生产高质量的根移栽。从1994年到2004年，美国温室种植者进口的无根插枝的批发价值增加了315% （USDA， 2005年）。2004年，美国温室种植者进口了超过7.66亿根一年生植物和多年生植物的无根插枝，据报道批发价值为5500万美元。温室种植者对库存植物的管理技术以及采收、储存和运输这些插枝的方法影响不大，但可以改进无根插枝的繁殖方式，以减少生根时间，提高生根质量，从而提高盈利能力。显然，要在尽可能短的时间内获得高质量的有根移栽，插枝必须快速、均匀、丰富地生根。营养插枝需要最少的光照来为根系的形成和发育提供能量。低于这个最小值的光照强度会导致根系生长和发育很少或根本没有，从而导致作物延迟生长或生根失败。Costa和Challa（2002）表明根系生长只受当前光合作用的影响，而不受先前在叶片中形成的储备的影响。反之，过多的光照会因插枝受到过多的水分和温度胁迫而抑制根的形成，并使叶片漂白（Lovell et al., 1972; Joeright et al., 2001; Enfield, 2002）。在几种草本和木本植物中，研究了扦插繁殖过程中日光照积分（DLI）或光照强度对生根率、根数和根质量、茎伸长和茎质量以及新梢生长的影响，包括掌槭（Behrens, 1988）、吉菲拉（Gypsophila paniculata， Islam和Willumsen， 2001）、木槿（Kachecheba, 1976）、牵牛花扦插（Cabaleiro和Economou， 1992）、夹竹桃（Phlox paniculata, Enfield, 2002）、栎树(Zaczek等。1999)和杜鹃花（戴维斯和波特，1987）。我们的目的是量化DLI对流行的矮牵牛花‘紫冰’的生根和芽生长的影响。在这里，我们给出了一次复制后的初步结果。人工照明的研究进展。人造照明的研究进展[c] . R. Moe学报。711，iss 2006 370材料和方法库存植物管理矮牵牛花“紫罗兰冰”库存植物保存在密歇根州立大学的植物科学研究温室中。（42 oN lat）在20±2℃下，在12 h的光周期下，平均DLI为11.3 mol·m·d。光周期为每天9 h，由白炽灯的日间延伸照明（树冠水平≈2 μmol·m·s）完成。每天1700 HR拉不透明黑布，0800 HR开布。从0800到1700 HR，当室外PPF <140 μmol·m·s时，高压钠灯在株高处提供了≈150 μmol·m·s的补充光合光子通量（PPF）[用光量子传感器（Apogee Instruments, Inc., Logan, Utah）测量]。每个工作台的温度由一个热电偶在一个吸气腔中每10秒测量一次，每小时的平均值由CR-10数据记录器（坎贝尔科学公司，洛根，犹他州）记录。乙烯利（Florel; Rhone-Poulenc Ag Company）以每四周150 mg·L的速率施用，以维持营养生长。在15厘米（1.3升）的圆形容器中种植植物（Dillen Products, Middlefield, Ohio），容器中填充了含有70%泥炭苔藓、21%珍珠岩和9%蛭石的混合物（Sure-Mix, Michigan Grower Products, Galesburg, Michigan）。根据需要用反渗透水补充水溶性肥料灌溉植株，以提供以下（mg·L）： 125 N, 12 P, 100 K, 65 Ca， 1.0 Fe和Cu， 0.5 Mn和Zn， 0.3 B和0.1 Mo （MSU Special, Greencare Fertilizers, Chicago, illinois）。2004年10月25日，在1000 HR条件下，从砧木上收获均匀的3 cm无性矮牵牛扦插（≈150根）。扦插在72细胞（30ml）塞盘（Landmark Plastic Corporation, Akron, Ohio）中，在50%的商业泥炭（确定- mix； Michigan Grower Products, Galesburg, Michigan）和50%筛选过的粗珍珠岩（thermorock, East, Inc., New Eagle, Pa）混合物中繁殖。扦插在环境温度为25±2℃的温室中，光周期为12 h。12 h光周期由9 h自然日组成，自然日由软白色荧光灯（树冠水平≈3 μmol·m·s）延长。介质温度测量使用40表E型热电偶（TT-E-40; Omega Engineering Inc., Stamford, Conn.）。顶雾由环境计算机作为时间和累积PPF的函数来控制。顶雾含有反渗透水和水溶性肥料，提供以下（mg·L）： 50 N、8 P、42 K、22 Ca、1.0 Fe和Cu、0.5 Mn和Zn、0.3 B和0.1 Mo （MSU Special）。DLI环境使用无遮光或永久编织遮光布，在单个繁殖隔间上减少约30%，55%和70%的光（OLS 30,50和70；Ludvig Svensson, Charlotte， N.C.）。包含10个光电二极管的线量子传感器（远地点仪器）被直接放置在四个照明隔间下面的岩屑上方，以测量PPF。热电偶和线路传感器连接到CR10数据记录仪（Campbell Scientific, Logan, Utah），每10秒记录一次数据。繁殖8、12、16 d后各环境下的平均DLI分别为1.2、1.9、3.4、4.3；1.1、1.7、2.9、3.6；分别为1.2、1.9、3.4和3.9 mol·m·d。每个DLI处理在繁殖开始后8、12和16 d收获10个插枝。在收获时记录根数、最长根长度、茎长（从中位到茎尖）、总根和茎干质量。采用SAS version 8.0 （SAS Institute, Cary， N.C.）中的PROC REG程序对治疗方法进行线性回归分析。采用从开始繁殖到第8、12、16天采集数据的平均DLI进行回归分析。回归分析使用所有观察值，而不是治疗方法。
Light intensity is often reduced during propagation of nonrooted herbaceous cuttings to minimize temperature and water stress, but the effects of light quantity on rooting and cutting growth have not been quantified for horticulturally important annuals that are vegetatively propagated. Petunia Tiny Tunia ‘Violet Ice’ (Petunia ×hybrida) cuttings were propagated under a daily light integral (DLI) of 1.2 to 3.9 mol·m·d. DLI environments were created using no shade or 30, 55, and 70% woven shade cloth. All cuttings were rooted in a glasshouse with overhead mist, maintained at 25 oC with a vapor pressure deficit of 0.3 kPa. A 12-h photoperiod was delivered using a 9-h natural day extended with light from soft-white fluorescent lamps. Rooting and growth evaluations of cuttings were made 8, 12 and 16 d after stick. Rooting and quality of cuttings increased when the DLI under which they were propagated increased. For example, after 16 d of propagation an increase in DLI from 1.2 to 3.9 mol·m·d decreased cutting shoot length from 6.3 to 4.1 cm, increased average root number from 17 to 36, and increased average length of the longest root from 9.4 to 12.9 cm. Root and shoot dry weight of cuttings harvested after 16 d of propagation increased by 452% and 47%, respectively, as the DLI increased. Therefore, the DLI during propagation should be properly managed to reduce rooting time and produce high quality rooted transplants. INTRODUCTION From 1994 to 2004, the wholesale value of nonrooted cuttings imported by U.S. greenhouse growers increased by 315% (USDA, 2005). In 2004, greenhouse growers in the U.S. imported over 766 million nonrooted cuttings of annuals and perennials with a reported wholesale value of US$55 million. Greenhouse growers have little influence on the stockplant management techniques and the methods employed to harvest, store, and ship these cuttings, but improvements can be made in how nonrooted cuttings are propagated to reduce rooting time, increase rooting quality, and consequently increase profitability. Clearly, to obtain high-quality rooted transplants in the shortest possible time, cuttings must root quickly, uniformly, and abundantly. Vegetative cuttings require a minimum quantity of light to provide the energy for root initiation and development. Light intensities below this minimum result in little or no root growth and development, leading to a delayed crop or rooting failure. Costa and Challa (2002) show that root growth is only affected by current photosynthesis and not by reserves formed previously in leaves. Conversely, too much light can inhibit root formation due to excessive water and temperature stress on the cuttings, and can bleach leaves (Lovell et al., 1972; Joeright et al., 2001; Enfield, 2002). The effects of daily light integral (DLI) or light intensity during propagation of cuttings on rooting percentage, root number and mass, stem elongation and mass, and shoot growth has been studied in several herbaceous and woody species, including Acer palmatum (Behrens, 1988), Gypsophila paniculata (Islam and Willumsen, 2001), Hibiscus sp. (Kachecheba, 1976), petunia cuttings (Cabaleiro and Economou, 1992), Phlox paniculata (Enfield, 2002), Quercus sp. (Zaczek et al., 1999) and Rhododendron (Davis and Potter, 1987). Our objectives were to quantify the effects of DLI on rooting and shoot growth of the popular petunia Tiny Tunia ‘Violet Ice’. Here, we present preliminary results after one replication. Proc. V IS on Artificial Lighting Ed. R. Moe Acta Hort. 711, ISHS 2006 370 MATERIALS AND METHODS Stock Plant Management Petunia Tiny Tunia ‘Violet Ice’ stock plants were maintained in the Plant Science Research Glasshouses at Michigan State University, East Lansing, Mich. (42 oN lat.) at 20 ± 2 oC under a 12-h photoperiod and an average DLI of 11.3 mol·m·d. The photoperiod consisted of a 9-h day completed by day-extension lighting (≈2 μmol·m·s at canopy level) from incandescent lamps. Opaque black cloth was pulled at 1700 HR and opened at 0800 HR everyday. From 0800 to 1700 HR, high-pressure sodium lamps provided a supplemental photosynthetic photon flux (PPF) of ≈150 μmol·m·s at plant height [as measured with a light quantum sensor (Apogee Instruments, Inc., Logan, Utah)] when the outdoor PPF was <140 μmol·m·s. Temperature on each bench was measured by a thermocouple in an aspirated chamber every 10 s, and hourly averages were recorded by a CR-10 datalogger (Campbell Scientific, Logan, Utah). Ethephon (Florel; Rhone-Poulenc Ag Company) was applied at a rate of 150 mg·L every four weeks to maintain vegetative growth. Stock plants were grown in 15-cm (1.3-L) round containers (Dillen Products, Middlefield, Ohio) filled with a mix containing 70% peat moss, 21% perlite, and 9% vermiculite (Sure-Mix, Michigan Grower Products, Galesburg, Mich.). Plants were irrigated as necessary with reverse osmosis water supplemented with water-soluble fertilizer to provide the following (mg·L): 125 N, 12 P, 100 K, 65 Ca, 1.0 Fe and Cu, 0.5 Mn and Zn, 0.3 B, and 0.1 Mo (MSU Special, Greencare Fertilizers, Chicago, Ill.). Propagation Environment Uniform 3-cm vegetative petunia cuttings (≈150 cuttings) were harvested from stock on 25 Oct. 2004 at 1000 HR. Cuttings were propagated in 72-cell (30-mL) plug trays (Landmark Plastic Corporation, Akron, Ohio) in a 50% commercial peat (Sure-Mix; Michigan Grower Products, Galesburg, Mich.) and 50% screened coarse perlite (ThermO-Rock, East, Inc., New Eagle, Pa.) mix. Cuttings were rooted in a glasshouse with medium and air temperatures of 25 ± 2 oC under a 12-h photoperiod. The 12-h photoperiod consisted of a 9-h natural day extended with light from soft-white fluorescent lamps (≈3 μmol·m·s at canopy level) as described above. Medium temperature was measured using 40-gauge type E thermocouples (TT-E-40; Omega Engineering Inc., Stamford, Conn.). Overhead misting was controlled by an environmental computer as a function of time and accumulated PPF. The overhead mist contained reverse osmosis water and water-soluble fertilizer to provide the following (mg·L): 50 N, 8 P, 42 K, 22 Ca, 1.0 Fe and Cu, 0.5 Mn and Zn, 0.3 B, and 0.1 Mo (MSU Special). DLI environments were created using no shade or permanent woven shade cloth that reduced light by ~30, 55, and 70% (OLS 30, 50 and 70; Ludvig Svensson, Charlotte, N.C.) over individual propagation compartments. Line quantum sensors containing 10 photodiodes (Apogee Instruments) were placed directly above the cuttings under each of the four lighting compartments to measure the PPF. Thermocouples and line sensors were connected to a CR10 data logger (Campbell Scientific, Logan, Utah), and data were recorded every 10 s. The average DLI under each environment after 8, 12 and 16 d of propagation was 1.2, 1.9, 3.4, 4.3; 1.1, 1.7, 2.9, 3.6; and 1.2, 1.9, 3.4 and 3.9 mol·m·d, respectively. Data Collection and Analysis Ten cuttings per DLI treatment were harvested 8, 12, or 16 d after the start of propagation. The number of roots, length of the longest root, shoot length (from the media level to the shoot apex), total root and shoot dry mass were recorded at harvest. Linear regression analysis on treatment means was performed using PROC REG procedures in SAS version 8.0 (SAS Institute, Cary, N.C.). The average DLI from the beginning of propagation to data collection on day 8, 12 and 16 were used in regression analysis. Regression analysis was performed using all observations, not treatment means.