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Open access

Irvin E. Widders and Hugh C. Price

Abstract

Pickling cucumbers (Cucumis sativus L. cvs. Tamor and Castlepik) were direct-seeded at six plant densities (in thousands, 44, 77, 97, 121, 152, 194) using two between-row spacings (71 and 36 cm) and three within-row spacings (29, 14, and 11 cm between plants). Compared with the 29 cm within-row spacing, the 11- and 14-cm spacings resulted in significantly lower total above-ground plant dry weights, growth rates, and total leaf areas for both cultivars as early as 21 to 27 days after planting. The between-row spacing effects on plant growth were similar, but were of a lower magnitude and appeared later in plant development than for the within-row spacing effects. Leaf lamina and fruit tissue exhibited the largest reduction in tissue dry weights per plant compared to stem and petiole tissue when plant density was increased from ≈4.5 to 20 plants/m−2 (45,000 to 200,000 plants/ha). Lower fruit productivity per plant at higher plant densities resulted from fewer fruit set per plant and lower fruit : shoot ratios. Unit leaf rate (g dry weight/day per g of lamina dry weight) was not affected by plant spacing during the fruit development period. Increased densities resulted in significantly higher leaf area indexes, and vegetative and total above-ground dry weights/m−2. Total fruit yield with a single harvest did not increase above ≈77,000 plants/ha for both cultivars. A high correlation (r = 0.877) between leaf lamina dry weight and fruit growth rate indicates that net photosynthetic capacity might be limiting fruit productive potential in pickling cucumbers.

Free access

Hector R. Valenzuela, Stephen K. O'Hair, and Bruce Schaffer

Abbreviations: DAP, days after planting, LAI, leaf area index; PPF, photosynthetic photon flux SLA, specific leaf area. 1 Present address: Dept. of Horticulture, Univ. of Hawaii, Honolulu, HI 96822. Florida Agricultural Experiment Stations Journal

Free access

S. Jiménez and M.T. Lao

The plant quality in function of the ratio nitrate:ammonium has been studied. The experiment was carried out in a recicling system in a Buried Solar Greenhouse. Dieffenbachia amoena `Tropic Snow' was cultivated in expanded clay substrate. The parameters considered to evaluate the quality have been plant height, leaf area index (LAI), leaf area ratio (LAR), leaf weight ratio (LWR), biomass, shoot to root ratio, number of buds, number of leaves, leaf length and width, leaf color, variegation, and ornamental visual quality evaluated by a group of experts and consumers. The rehearsed NO3-:NH4 + ratios has been 100:0, 50:50, and 0:100. The amoniacal form improves the following productive parameters: plant height, LAI, biomass, number of leaves, number of buds and color of the leaf, as well as the visual quality as much for experts as for consumers.

Free access

Laurie Hodges, Mohd Nazip Suratman, James R. Brandle, and Kenneth G. Hubbard

The effects of wind protection on growth and total and marketable yields of snap bean (Phaseolus vulgaris L.) planted at 2-week intervals through the 1994 and 1995 growing seasons were examined. Research was conducted under nonirrigated conditions at the Shelterbelt Research Area, Univ. of Nebraska Agricultural Research and Development Center (ARDC) near Mead. `Strike' (white-seeded) and `Rushmore' (dark-seeded) were planted in locations sheltered from wind stress by tree windbreaks (shelterbelts) and in locations exposed to normal winds using a randomized complete-block design with a split-split plot arrangement of treatments. Air temperature, soil temperature, humidity, wind speed, and wind direction were monitored. Detailed microclimate conditions at bean canopy level in sheltered and exposed plots are provided in the text. Wind speed in sheltered areas averaged 36% of open field wind speed in 1994 and 43% of open wind speed in 1995. Soil temperatures were higher in sheltered areas than in exposed areas. Microclimate changes due to shelter had no effect on the percent seedling emergence or number of days to emergence. Plants in shelter had significantly higher total dry weight and leaf area index and greater total internode length than exposed plants. Both total and marketable yields were increased significantly by production under sheltered conditions each year. Planting date and cultivar also had a significant impact on average pod yields. No interactions between shelter and planting date, or shelter and cultivar, were found in either year. The results suggest that wind protection provided by shelterbelts (tree windbreaks) can increase pod yields of snap bean both early and late in the season. This may result in greater profit for the grower due to a tendency for higher prices at these times.

Free access

David E. Yarborough and Prasanta C. Bhowmik

Abbreviations: C: W, crop : weed; DAT, days after transplanting; DW, dry weight; LAI, leaf area index; RYT, relative yield total. 1 Assistant Professor of Horticulture. 2 Associate Professor of Weed Science. Contribution no. 1342 of the Maine

Free access

Anke van der Ploeg, Susana M.P. Carvalho, and Ep Heuvelink

converted into dry mass [i.e., light use efficiency (LUE)] and/or by increasing light interception due to a higher leaf area index (LAI). Thus far, little is known about the mechanisms responsible for increasing plant biomass at suboptimal temperatures

Open access

Jose F. Pereira and Walter E. Splittstoesser

Abstract

A rapid method to determine the total leaf area of a cassava (Manihot esculenta Crantz) plant was determined. A ruler was designed to determine individual leaf area when the linear equation relating leaf area and the length of the middle leaf lob is known. A linear equation can be developed for a specific cultivar. Total leaf area of a whole plant can be determined by counting the number of phylotactic turns and using it in a linear equation relating cumulative leaf area with the number of phylotactic turns per plant. Equations for 6 cassava cultivars are given.

Free access

William L. Bauerle and Joseph D. Bowden

This report describes a system for integrating photosynthetically active radiation (PAR) using fiberoptics. Many photoelectric sensors or 1-m-long line sensors that integrate individual interception points for spatial averaging were replaced with fiberoptics, which integrate interception points. Depending on the positioning of optical fibers and the amount of fibers terminated at a PAR sensor, whole-plant, canopy layer, and individual leaf light interception can be determined. The use of fiberoptics has the added advantage of being very small in comparison to the bulk of a typical quantum sensor. The fiberoptic-based system potentially is a more accurate, less expensive method to integrate PAR throughout plant canopies than PAR sensors.

Open access

Richard H. Merritt and Harry C. Kohl Jr.

Abstract

Geranium seedlings (Pelargonium × hortorum L.H. Bailey, ‘Mustang’) grown in 13 hr photoperiods were 23% taller due to stem and petiole elongation, had larger leaves, and prior to canopy closure had a higher crop productivity efficiency (CPE) than seedlings grown under 9 hr photoperiods. In general, the tallest plants were produced when grown with soil temperatures of 18°C. The highest weekly CPE attained was 3.8%.

Open access

David R. Hershey and Richard H. Merritt

Abstract

Seedlings of Begonia × semperflorens-cultorum Hort. ‘Scarletta’ were grown in a greenhouse at a plant density of 193 plants/m2. Crop productivity (grams of dry matter produced per day per square meter of crop) and crop productivity efficiency (percentage of the photosynthetic photon flux incident on the crop that is stored in the form of crop dry matter as energy of combustion) did not increase when the photoperiod was extended from 9 to 13 hr with incandescent lights. However, stem and petiole length did increase under 13- compared to 9-hr photoperiods. Crop productivity of begonia was less than maximum values reported for some other bedding plants. However, when crop growth was expressed in terms of fresh weight rather than dry weight, begonia crop growth exceeded that reported for other bedding plants. This increased growth seemed to be due to the low dry weight to fresh weight ratio in wax begonia of 0.03.