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Open access

José Cuenca, Andrés García-Lor, José Juárez, José A. Pina, Luis Navarro and Pablo Aleza

Open access

Géza Bujdosó, Attila Fodor and Anita Karacs-Végh

Open access

Jingli Gao, Fengyang Yu, Wenji Xu, Yuee Xiao and Xiaoying Bi

Open access

Lauren E. Kurtz, Jonathan D. Mahoney, Mark H. Brand and Jessica D. Lubell-Brand

Feminized hemp seed producers often use selfing to maintain a strain name; however, selfing may lead to inferior plants for cannabidiol (CBD) production. Using three different hemp strains as parents [Candida (CD-1), Dinamed CBD, and Abacus], two outcrosses [Candida (CD-1) × Abacus and Dinamed CBD × Candida (CD-1)] and one self-cross [Candida (CD-1) × Candida (CD-1)] were conducted to produce feminized seed. Progeny from the self-cross were significantly smaller and had less yield than outcrossed progeny. Selfed progeny were variegated and highly variable for total dry weight and floral dry weight. Discriminant analysis of principal components (DAPC) using amplified fragment length polymorphism (AFLP) separated the three progeny populations and showed that outcrossed populations clustered closer to the maternal parent, possibly the result of a maternal effect. Analysis of molecular variance (AMOVA) indicated that most variation (74.5%) was within populations, because the progeny from all three populations are half-siblings of each other. The selfed progeny population had lower expected heterozygosity (He = 0.085) than each of the outcrossed progeny populations (He ≈ 0.10). These results suggest that selfed progeny may demonstrate inbreeding depression resulting from enhanced expression of homozygous recessive traits. It may be beneficial for feminized seed producers to use outcrossing instead of selfing to generate feminized seed for CBD production.

Open access

Hui-qing Li, Qing-he Li, Lei Xing, Gao-jie Sun and Xiu-lian Zhao

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT50) using electrolyte leakage test (ELLT50) and triphenyltetrazolium chloride test (TTCLT50) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT50 was lower than the xylem TTCLT50, and the two sds were similar. The ELLT50 showed no significant correlation with any TTCLT50. For most species, the ELLT50 was higher than the cambium and phloem TTCLT50 and was not significant different with the xylem TTCLT50. The ELLT50 showed higher sd than any tissue TTCLT50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT50.

Open access

Rahmatallah Gheshm and Rebecca Nelson Brown

Romaine lettuce (Lactuca sativa) is the most popular leafy vegetable in the United States. Organic and synthetic mulch materials are applied by farmers to reduce their weeding expenditures, manage soil temperatures, and increase the yield and quality of their crops. This study examined the impacts of using black polyethylene, compost, and shredded leaves as surface mulches in spring open field romaine lettuce by using data regarding the soil temperature, lettuce growth, and yield parameters. Mulch treatments were compared to determine effects on soil temperature, lettuce growth rates, leaf area index (LAI), yield, and plant size. Experiments were conducted in 2017 and 2019. Soil temperatures were slightly (but significantly) warmer in 2019, the plants grew more rapidly, and LAI, yield, and plant size were all significantly greater than they were in 2017. Mean soil temperatures were 18.0 and 18.9 °C in black polyethylene mulched plots, 17.7 and 18.5 °C in compost, 17.5 and 17.0 °C in bare ground, and 16.9 and 17.3 °C in shredded leaf plots in 2017 and 2019, respectively. Changes in canopy size presented a similar trend over the growing season for all treatments; shredded leaf and bare ground treatments on all measuring dates had the smallest canopy size, and compost and black polyethylene mulches had the largest canopy sizes. Black polyethylene and compost mulches had the highest LAI and yields in both years. In 2017, the bare ground treatment was similar to black polyethylene and compost mulch treatments for both parameters, and all three treatments were significantly greater than the shredded leaf mulch treatment. In 2019, the bare ground treatment was similar to the shredded leaf mulch treatment and significantly lower than the black polyethylene and compost mulch treatments. In 2017, black polyethylene and compost mulches had LAI of 7.67 and 7.37 and yields of 6.38 and 6.68 kg·m−2, respectively. Bare ground had an LAI of 7.16 and yielded 5.94 kg·m−2. Shredded leaf mulch plots had the lowest LAI (5.94) and yield (4.96 kg·m−2). In 2019, the bare ground treatment had an LAI of 7.5 and yielded 7.6 kg·m−2. Black polyethylene and compost mulches increased LAI by 1.7. Yield increased by 2.8 kg·m−2 with black polyethylene mulch and by 2.4 kg·m−2 with compost mulch. Shredded leaf mulch produced LAI and yield similar to but slightly lower than bare ground. Dry weight, plant height, and head diameter in bare ground and shredded leaf mulch treatments were significantly smaller than in black polyethylene and compost mulch treatments. The cultivar rank order was consistent across treatments in both years; ‘Ridgeline’ grew significantly faster than ‘Coastal Star’, and plants were significantly larger at harvest. Black polyethylene suppresses weeds and increases soil temperatures, thereby enhancing yields of spring-to-summer romaine lettuce under southern New England conditions. Compost mulch has similar effects on yields. Shredded leaf mulch is effective at suppressing weeds but decreases soil temperatures and yields.

Open access

Yang Li, Juanqi Li, Guoxiu Wu, Yanman Li, Aimin Shen, Deli Ma and Shengli Li

In recent years, air circulation has been used in protected cultivation to improve the microenvironment around seedlings, which in turn enhances photosynthesis and seedling growth. However, a practical and precise air circulation device has not yet been reported, especially one for growing seedlings in a greenhouse. Considering the use of a seedbed in seedling cultivation, a blower that can move back and forth on the seedbed and accurately control the air velocity is designed. In this experiment, we take the nonblowing treatment as the control (CK); three air velocities (0.3, 0.6, and 0.9 m/s) were selected to investigate the effect of interval blowing on the microenvironment of the canopy, physiology of seedling growth, stomatal characteristics of leaves, and stem mechanics of tomato seedlings. The three air velocities were found to significantly reduce the canopy temperature by 0.44, 0.78, and 1.48 °C lower than the CK, respectively, and leaf temperature by 0.83, 1.57, and 2.27 °C lower than the CK, respectively, in cultivated seedlings during summer. The relative humidity of the tomato seedling canopy decreased by 2.7% to 7.0%. Compared with the CK, the plant height of tomato seedlings decreased by 13.54% and root dry mass, root-shoot ratio, and seedling quality index (SQI) increased by 34.63%, 21.43%, and 14.29%, respectively, at 0.6 m/s. In addition, mechanical indexes such as hardness and elasticity of the tomato seedling stem were higher under air disturbance than those of the CK. The best effect was seen in the treatment with the air velocity of 0.6 m/s, in which the hardness and elasticity of the stem base and the first node were significantly higher than that of the CK. In conclusion, air disturbance generated by the air blowing device we designed effectively improved the microenvironment around the plants, enhanced the physiological activity of the seedlings, and thereby promoted seedling growth.

Open access

İbrahim Kahramanoğlu and Chunpeng Wan

Little mallow (Malva parviflora L.) has been traditionally used as an alternative food source. To the authors’ knowledge, there is no available published information about the postharvest storability of little mallow. This study was conducted in three steps. It aimed to determine the postharvest storability of little mallow leaves and to improve its storability using different strategies. First, the effects of four different storage conditions on the storability of little mallow leaves were tested to determine the most favorable conditions for further studies: 5 ± 1 °C and 95% relative humidity (RH); 9 ± 1 °C and 95% RH; 13 ± 1 °C and 95% RH; and 24 ± 1 °C and 55% RH as control. Preliminary experiments suggested that the best temperature and RH combination is 9 ± 1 °C and 95% RH. Hence, the effects of hot water dipping (HWD) were tested at three different temperatures (40, 45, and 50 °C) for two different durations (60 and 120 seconds); the results suggested that the 40 °C treatment is the most suitable heat treatment for improving the storability of mallow. The final experiments were conducted with 15 different treatments, including HWD, eco-friendly edible bio-materials, modified atmosphere packaging, and ultraviolet radiation. Results showed that low-density polyethylene (LDPE) (60 × 60 cm; thickness, 50 μ) and polypropylene (PP) (35 × 50 cm; thickness, 35 μ) packaging provide the highest efficacy for preserving overall quality. The edible quality of little mallow can be extended to 15 days with PP and 12 days with LDPE. However, both materials caused an abnormal odor after that time. Further studies involving additional edible coatings are necessary to determine if the storage duration of little mallow leaves could be extended.

Open access

Lloyd L. Nackley, Elias Fernandes de Sousa, Bruno J.L. Pitton, Jared Sisneroz and Lorence R. Oki

Potted poinsettia (Euphorbia pulcherrima) is an important commercial commodity for the U.S. floriculture industry. The production of poinsettia demands intensively managed light control, heat, fertilizer, and water; inhibiting elongation with plant growth regulators, and protecting plants from diseases and pests with pesticide applications. Excessive irrigation creates pollution, promotes disease, and is expensive. Sensor-based control systems can optimize irrigation schedules. Irrigation management is crucial in nursery production of poinsettias because water is a limited resource and agricultural runoff is monitored in many states across the United States. By pairing environmental sensors with sensors that continuously monitor plant transpiration, we can determine how plant water use and water stress fluctuate with environmental and physiological demands. We hypothesized that continual measurements of sap flow could be correlated with environmental sensors to develop a new water stress index (WSI), which can deliver the benefits of detecting water stress that might affect the quality of potted poinsettias. To test this hypothesis, rooted cuttings of poinsettia (E. pulcherrima cv. Prestige Red) were individually potted into twelve 11-L black plastic nursery pots. Potted plants were grown in a naturally illuminated temperature-controlled glasshouse. The 12 plants were randomly assigned one of three watering treatments: weekly, biweekly, and triweekly irrigation. From the data collected, we were able to create a WSI that correlated available soil moisture with the difference between the expected transpiration with actual transpiration rates. Our results suggest that the plants in the weekly treatment group did not experience water stress until 0.3 m3·m–3 volume water content indicated by <0.2 WSI. These results support previous research that found 0.1 to 0.3 m3·m–3 can be stressful soil moisture conditions for greenhouse-grown crops. Results also show that for substrates with similar substrates that irrigation set points can be reduced to 0.2 m3·m–3 for improved irrigation efficiency.

Open access

Yuting Zou, Yanan Wang, Mingwei Zhu, Shuxian Li and Qiuyue Ma

Paeonia ostii is a woody oil crop with potential value as an edible oil. With the aim of acquiring systematic knowledge of the development of P. ostii seeds, the oil content, biomass, and water content of the seeds were determined. Changes in the distribution of hydrogen protons in P. ostii seeds during follicle development were traced using magnetic resonance imaging (MRI). The formation of oil bodies in the endosperm and embryo was observed using transmission electron microscopy (TEM). Dynamic changes in oleic acid, linoleic acid, and α-linolenic acid contents were assessed by gas chromatography-mass spectrometry (GC-MS). The magnetic resonance images showed that, during early follicle development [45–85 days after flowering (DAF)], a greater quantity of liquid mucus was present within the seeds, and seeds in the same follicle developed at different rates. At 95 to 115 DAF, proton density was distributed evenly in all areas of the seed. A small dark area appeared in the center of the seed, and mucus in the follicles and water in the pericarp disappeared gradually. TEM observations showed that at 45 DAF, a few oil bodies were scattered at the cell periphery in the endosperm, and oil bodies were more numerous in the embryo. With the progression of seed development, the number and size of oil bodies in the embryo and endosperm continued to increase. The fresh and dry mass of P. ostii seeds increased from 45 to 105 DAF, then decreased after 105 DAF. The moisture content decreased, whereas the oil content increased and attained 33.1% at seed maturity. The three predominant unsaturated fatty acids accumulated simultaneously and showed stages of initial accumulation (45–65 DAF) and rapid accumulation (65–105 DAF). The results suggest that 65 to 105 DAF is a critical period for unsaturated fatty acid accumulation in P. ostii seeds.