Browse

You are looking at 1 - 10 of 28,484 items

Open access

Muhammet A. Gündeşli

Open access

Yunmi Park, Seok-Woo Lee, Soon-ho Kwon and Hae Yun Kwon

Open access

Kristin E. Gibson, Alexa J. Lamm, Fallys Masambuka-Kanchewa, Paul R. Fisher and Celina Gómez

There are economic and knowledge-based challenges that must be addressed for indoor farms to be viable in the United States despite their potential benefits. A mixed-methods approach was used to identify the needs of specialty crop growers and stakeholders interested in or currently using indoor propagation environments to grow seedlings, cuttings, and tissue-cultured plants. An online survey evaluated specialty crop growers’ current use of indoor plant propagation environments and their needs related to indoor plant propagation. A focus group was then conducted to further understand the needs for indoor plant propagation by stakeholders. Industry participants were largely motivated to adopt indoor propagation environments to reduce crop losses (“shrinkage”), increase productivity per unit of land area, ensure faster germination or rooting, improve plant quality, and profit from anticipated economic benefits. Research and education priority areas identified by stakeholders included economic costs and benefits (including capital investment and energy costs), improved crop quality, production time, uniformity, reduced shrinkage, and strategies to improve light management indoors. Based on the results, research efforts must determine and prioritize the most important economic considerations and production advantages to fill important gaps in knowledge about indoor plant propagation.

Open access

Mary Ann D. Maquilan, Dominick C. Padilla, Donald W. Dickson and Bala Rathinasabapathi

Bell and chili peppers are important vegetable and spice commodities worldwide. Significant yield reductions have been attributed to damage caused by root-knot nematodes (RKNs; Meloidogyne spp.). This study addresses the need for developing pepper varieties that have high resistance to RKN, which is now of increasing importance due to restrictions on the use of fumigant nematicides. Our goal is to provide a nonchemical alternative to sustain commercial pepper production in Florida, which is a major producer of peppers in the United States. We evaluated ‘UFRJ107(6)A3’, an advanced inbred line developed from a cross between Capsicum annuum L. ‘Jalapeno’ and ‘Round of Hungary’, for resistance against the nematode in comparison with the parental and three other Capsicum cultivars, namely, C. annuum ‘Charleston Belle’, ‘California Wonder’, and C. chinense Jacq. ‘Datil’ in two separate growth chamber experiments. Based on egg mass indices and reproduction factors, ‘UFRJ107(6)A3’ was significantly more resistant to M. incognita compared with the other five cultivars. When tested with five RKN species, ‘UFRJ107(6)A3’ showed comparably high levels of resistance to M. arenaria and M. floridensis as ‘California Wonder’ based on the nematode reproduction factor. In ‘UFRJ107(6)A3’, however, there were no detectable M. arenaria egg masses, and M. incognita reproduction was minimal compared with that of ‘California Wonder’; both cultivars supported the reproduction of M. enterolobii and M. javanica, although the reproduction factors of M. enterolobii were ≈10-fold higher than M. javanica. To characterize the mechanism of high resistance to M. incognita in ‘UFRJ107(6)A3’, we examined the extent to which infective second-stage juveniles (J2s) were able to penetrate its roots in comparison with the susceptible ‘California Wonder’ and ‘Datil’ in two independent experiments; we conducted RKN root penetration assays with a single plant in a pot and two plants in a single-pot choice test using ‘Datil’ and ‘California Wonder’, respectively, as susceptible standards. In both assays, M. incognita J2s were absent in the roots of ‘UFRJ107(6)A3’ 7 days after inoculation but were present in the susceptible cultivars, indicating that resistance has an effect at the root invasion stage. In growth chamber experiments, at constant temperatures of 28 and 30 °C, ‘UFRJ107(6)A3’ exhibited M. incognita resistance superior to its parents and to the standard resistant bell pepper ‘Charleston Belle’, thus offering the potential to enhance specialty pepper production and for use as a nematode-resistant rootstock for commercial bell peppers.

Open access

Rhuanito Soranz Ferrarezi, Thomas C. Geiger, Jayar Greenidge, Shamali Dennery, Stuart A. Weiss and Gustavo H.S. Vieira

Drip irrigation presents higher distribution efficiency than sprinkler irrigation. Proper system design and the use of pressure-compensating emitters have important roles in irrigation uniformity and efficiency, which directly affect plant growth. This study evaluated the performance of four pressure-compensating and noncompensating emitters and the effects of these irrigation equipment on the yield of three okra [Abelmoschus esculentus] varieties cultivated in the U.S. Virgin Islands. Trials were performed in two seasons (Spring and Fall 2016), and tested four types of irrigation equipment (flow control drip tape, thin wall drip line, thin wall drip tape, and heavy wall drip line) and three varieties of okra (‘Clemson Spineless 80’, ‘Clemson Spineless’, and ‘Chant’), arranged on a complete randomized block design with three replications. Irrigation was performed based on reference evapotranspiration and measured daily using an automated weather station. Soil moisture, electrical conductivity (EC), and soil temperature were monitored using capacitance sensors. The ability of the irrigation equipment to increase pressure was evaluated in the laboratory, in experimental modules using clean water, and while simulating three different slopes (leveled, uphill, and downhill). In the field trial, yield and leaf physiological parameters were influenced by season (P < 0.05) and the percentage of the marketable yield was influenced by variety (P < 0.05); however, fruit morphological parameters and soluble solids content were variety-dependent (P < 0.01). The pressure-compensating emitters maintained water flow within the range indicated by the manufacturers when used within the recommended pressure range. Distribution uniformity decreased over time for all equipment except the heavy wall drip line in Fall 2016. Irrigation equipment did not impact okra morphological attributes and yield, indicating that the same productivity can be successfully maintained while improving irrigation efficiency. Equipment should be selected based on price and irrigation efficiency to reduce the amount of water used.

Open access

Ittetsu Yamaga and Sakura Hamasaki

Ponkan (Citrus reticulate) and Tachibana (Citrus tachibana) contain large amounts of polymethoxyflavones (PMFs). To produce highly functional food with high potential, it is important to develop technologies to increase their PMF content. Nobiletin content of the flavedo changed in harvested ‘Ohta Ponkan’ fruits after ultraviolet (UV)-C irradiation and PMF content increased for only the first 2 days following irradiation. The effect of UV-C or UV-B irradiation on PMF content at each harvest time (UV-C, July to December; UV-B, July to September) was observed in Ponkan and Tachibana. We found that UV-C had the greatest impact earlier in the season. The effects of UV-B irradiation were similar to UV-C results. Therefore, it is beneficial to harvest early and extract PMFs from fruit 24 hours after UV-C irradiation.

Open access

Chad E. Finn, Bernadine C. Strik, Brian M. Yorgey, Mary E. Peterson, Patrick A. Jones, Jungmin Lee, Nahla V. Bassil and Robert R. Martin

Open access

Zhixiong Zeng, Jiaming Guo, Xinyu Wei, Enli Lü and Yanhua Liu

Mechanical ventilation systems are applied in greenhouses for temperature adjustment, but they consume a large amount of energy. This research aims to optimize the energy consumption of a variable air volume (VAV) fan-pad evaporative cooling system via experimentation. We discuss the effects of adjusting the VAV fan-pad evaporative cooling system on temperature and humidity, and we provide an estimate of the corresponding energy consumption under different highest stable temperature conditions. The test results demonstrate that a higher fan frequency is typically accompanied by greater ventilation quantity, faster cooling speed, more pronounced effects of the fan-pad evaporative cooling system fan, and more intensive energy consumption during the cooling process compared with a low fan frequency. When the temperature increased for 71 seconds or 60 seconds in a specific temperature zone (34 to 35 °C), the indoor temperature could be reduced to the optimum for crops with a fan frequency of 20 Hz, saving more than 87% of the energy output. When the warm-up time for a specific temperature zone (34 to 35 °C) was 41 seconds, the indoor temperature could be reduced to the optimum temperature for crops only when the fan frequency was 50 Hz. The VAV fan-pad evaporative cooling system increased the relative humidity in the greenhouse to satisfy crop production demands. The temperature of crops shared the same variation trend as temperatures inside the greenhouse. Our research results theoretically benefit cooling control and energy-saving design of greenhouses in the subtropics.

Open access

Xiongwen Chen and Hua Chen

Chinese Torreya (Torreya grandis cv. Merrillii) is an important economic tree in China, but there are limited studies on its seed production. We analyzed the patterns of historical seed production at two major sites (Zhaojiazhen and Jidongzhen) for Chinese Torreya from different perspectives. The results indicated that there were no 3-year or multiyear cycles in its seed production. A positive correlation existed between the average seed production and the average annual air temperature in 5 or 10 years at both study sites. There was no trend of the increasing coefficient of variance (cv) in seed production, but the cv generally increased before 1975, and became flat after that time. Frequency power law existed in seed production at both sites, but Taylor’s Law existed only at Zhaojiazhen. The multiscale entropy decreased with time scales, and the patterns were similar at both sites. Our research results provide a new understanding of seed production for Chinese Torreya.

Open access

Qinglu Ying, Yun Kong and Youbin Zheng

To facilitate machine harvest for labor savings, the height of microgreens needs to reach ≈5 cm. Recent studies indicate that monochromatic blue light (B) can promote stem elongation similar to far-red light (FR). To examine whether nighttime B treatments can promote plant elongation without compromising yield and quality, mustard (Brassica juncea) and arugula (Eruca sativa) microgreens were grown under different light-emitting diode (LED) lighting regimes in a growth chamber. The 16-hour daytime lighting comprised 20% B and 80% red light (R), and had a total photosynthetic photon flux density (PPFD) of 300 µmol·m–2·s–1 at canopy level. During the 8-hour nighttime, the plants were exposed to the following treatments: 1) dark (D) as one control; 2) 4 hours of B at 40 µmol·m–2·s–1 followed by 4 hours of darkness (40B-D); 3) 4 hours of darkness followed by 4 hours of B at 40 µmol·m–2·s–1 (D-40B); 4) 8 hours of B at 20 µmol·m–2·s–1 (20B); 5) 8 hours of B + FR, and each of them at 20 µmol·m–2·s–1 (20B20FR); and 6) 8 hours of FR at 20 µmol·m–2·s–1 (20FR) as another control. The plants were harvested after 11 days of treatment. Nighttime B treatments (40B-D, D-40B, and 20B), compared with D, increased plant height by 34% and 18% for mustard and arugula, respectively, with no difference among the three B treatments. The combination of B and FR (20B20FR), compared with B alone, further increased plant height by 6% and 15% for mustard and arugula, respectively, and showed a similar promotion effect as 20FR. Plant height did not meet the machine harvest requirement for both species with the D treatment, but did so for mustard with the nighttime B treatments and for arugula with the 20B20FR treatment. There was no difference in biomass among all treatments except that 20B, compared with D, increased the fresh weight (FW) of arugula by 12%, showing a similar promotion effect as 20FR. Despite a greater promotion effect on elongation than B alone, 20FR reduced the leaf index compared with D. However, B alone or the 20B20FR treatment increased leaf thickness compared with D, and increased chlorophyll content index (CCI), leaf index, dry matter content, and leaf thickness to varying degree with species, compared with 20FR. Overall, nighttime B alone, or its combination with FR, promoted microgreen elongation without compromising yield and quality.