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  • Author or Editor: Qi Zhang x
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Fifteen tall, warm-season, native and ornamental grasses were subjected to a 3-year, low-input, and cold hardiness trial conducted from 2010 to 2013 in zone 4a at Fargo and Mandan, ND. Grasses tested were big bluestem [species (Andropogon gerardii)], ‘Pawnee’ big bluestem (A. gerardii), silver banner grass (Miscanthus sacchariflorus), giant miscanthus (Miscanthus ×giganteus), hardy pampas grass, (Saccharum ravennae), and the following maidengrass (Miscanthus sinensis) cultivars: Silver Feather, Narrow Leaf, Blondo, Autumn Light, Condensatus, Grosse Fontaine, Morning Light, Gracillimus, Strictus, and Zebrinus. In addition to survival, the grasses were also rated for spring vigor and fall quality (0–10 scale for both evaluations), fall leaf length, and fall flower height. The grasses received no management during the trial other than irrigation during the first season and weed control. The grasses were exposed to subsurface soil temperatures (at 6-inch depth) that reached as low as −8.6 °C at the Fargo location and −6 °C at the Mandan location. The study revealed that all big bluestem (species), ‘Pawnee’ big bluestem, and silver banner grass survived at both locations; silver banner grass scored the highest spring vigor ratings; silver banner grass and ‘Pawnee’ big bluestem scored the highest fall quality ratings; silver banner grass produced the longest fall leaf length; and ‘Pawnee’ big bluestem, big bluestem (species), and silver banner grass produced the tallest fall flowers.

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It is known that the redistribution of water and the formation of dispersed water units appears to be a prerequisite for deep supercooling. A concentration of the cell solute results from the migration of water during extracelullar freezing and lowers the temperature of homogeneous nucleation, but we are convinced that nucleation of ice within cells may be initiated by a heterogeneous mechanism, except we consider a small spherical cave, the water can freeze on the wall of this cave. We are also convinced that the solid walls of the capillary exert an external potential on the water molecules, causing the shift of the triple point of the confined fluids. Based on Fletcher's work for spherical particle, we have gotten the formula of critical free energy in the process of heterogeneous nucleation of water in a small spherical cave. This presentation introduces the theoretical background and counts the drop of temperature in heterogeneous nucleation. Then, putting two actions (depression of triple point and process of heterogeneous nucleation) together, we have calculated the freezing point. Sometimes it is lower than –38 °C. Some phenomena can be explained by using this theory: 1) Water is at the tension status, which means that it wets plant tissue, so the triple point (melting point) of tissue water can be lowered. 2) The redistribution of water, formation of dispersed water units, and dry region preventing ice from propagating, all allow heterogeneous nucleation, then the two actions can be synthesized and the water would lead to deep supercooling. If the barriers were destroyed, heterogeneous nucleation and deep supercooling would certainly be lost. 3) This theory is only suited to rigid wall of small cave, so we understand why cell wall rigidity has been shown to affect freezing characteristics. Project 39870234 supported by National Nature Science Foundation.

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The application of diffuse light can potentially improve the homogeneity of light distribution and other microclimatic factors such as temperature inside greenhouses. In this study, diffuse light plastic films with different degrees of light diffuseness (20% and 29%) were used as the south roof cover of Chinese solar greenhouses to investigate the spatial distribution of microclimatic factors and their impacts on the growth and yield of tomato. The horizontal and vertical photosynthetic photon flux density (PPFD) distributions, air temperature distribution, and leaf temperature distribution inside the canopy, tomato leaf net photosynthesis (Pn), and fruit production during the growth period were determined. The results showed that diffuse light plastic film continuously improved the light distribution in the vertical and horizontal spaces of the crop canopy in terms of light interception and uniformity. A more diffuse light fraction also decreased the air and leaf temperatures of the middle canopy and upper canopy during the summer, thereby promoting the photosynthesis of the tomato plants. Pn of the middle and lower canopies with higher haze film were significantly greater than those with lower haze film (19.0% and 27.2%, respectively). The yields of higher stem density and lower stem density planted tomatoes in the 29% haze compartment were increased by 5.5% and 12.9% compared with 20% in the haze group, respectively. Diffuse light plastic films can improve the homogeneity of the canopy light distribution and increase crop production in Chinese solar greenhouses.

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Hydrangea macrophylla is the most popular species in the genus Hydrangea because of its large and brightly colored inflorescences. Since the early 1900s, numerous cultivars with showy flowers have been selected. Although many H. macrophylla cultivars have been developed, cold hardiness is still the major limitation to their outdoor use. Hydrangea arborescens is a small attractive shrub or subshrub native to northeastern parts of the United States, which is valued for its hardiness. Interspecific breeding of H. arborescens and H. macrophylla has been tried, but putative hybrid seedlings either died at an early stage or were not verified. We made successful hybridizations between H. macrophylla ‘Blue Diamond’ and H. arborescens ‘Annabelle’ and used in vitro ovary culture to produce viable plants. Hybrids were intermediate in appearance between parents, but variable in leaves, inflorescences, and flower color. The success of this hybridization was confirmed by six simple sequence repeat (SSR) genetic markers. The maternal chromosome number was 36, and the paternal number was 38. Chromosome counts of hybrids indicated that nearly half of them were aneuploids. Male fertility of progeny was evaluated by fluorescein diacetate staining of pollen. Twelve out of 14 hybrids (85.7%) had male fertility. We documented the first flowering progeny of H. macrophylla and H. arborescens, suggesting an effective beginning to a cold hardiness breeding program.

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Different pollinators exhibit different adaptability to plants. Here, we compared the performance in visiting frequency and pollination efficiency among three bee pollinators (Bombus terrestris, Apis cerana, and Apis mellifera) on greenhouse-grown northern highbush ‘Bluecrop’ blueberry plants and evaluate their effects on yield and fruit quality. Our results indicated that the duration of daily flower-visiting of B. terrestris was 24 and 64 minutes longer than that of A. cerana and A. mellifera, respectively, and the visiting time of a single flower for B. terrestris was substantially shorter than the other two bee species, and pollen deposition on the stigma from single visit by B. terrestris was twice and three times that of A. cerana and A. mellifera, respectively. The yield of individual plants pollinated by B. terrestris showed an increase of 11.4% and 20.0% compared with the plants pollinated by A. cerana and A. mellifera, respectively, with the rate of Grade I fruit (>18 mm diameter) reaching 50.8%, compared with 32.9% and 22.5% for A. cerana and A. mellifera groups, respectively. Moreover, the early-to-midseason yield of plants pollinated by B. terrestris was higher, and the ripening time was 3 to 4 days earlier. An artificial pollination experiment demonstrated that seed set of high (≈300), medium (90–110), and low (20–30) pollination amounts were 43.0%, 42.5%, and 10.5%, respectively, and the corresponding mean weights of single fruits (related to the seed number inside) were 2.8, 2.7, and 1.2 g, respectively. The highly efficient pollination of B. terrestris was attributed to its behavior of buzz-pollination. Therefore, it is preferential for pollination of ‘Bluecrop’ blueberry in the greenhouse.

Open Access

Leaves of Begonia semperflorens accumulate anthocyanins and turn red under low temperature (LT). In the present work, LT increased H2O2 content and superoxide anions production rate, causing significant increases in the activities of enzymes and contents of reduced components involved in the ascorbate-glutathione cycle (AsA-GSH cycle). As a result, LT-exposed seedlings increased the expression of genes involved in anthocyanin biosynthesis, and accumulated anthocyanin. Based on LT condition, application of N,N'-dimethylthiourea (DMTU) decreased reactive oxygen species (ROS) content, and unbalanced the AsA-GSH-controlled redox homeostasis. As a result, seedlings in the LT + DMTU group did not accumulate anthocyanin. Our results suggest that ROS may act as an important inducer in LT-induced anthocyanin biosynthesis.

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We investigated a practical method for immobilizing liquid spawn of oyster mushroom (Pleurotus ostreatus) to prolong the storage time and provide convenient transportation of liquid spawn of edible mushrooms. The method was based on the mycelial pellets of liquid spawn adsorbed in carriers. Selected carriers were similar to cultivation substrates, and the best carrier was a mixture of cottonseed hull, corn core, and wheat bran with a ratio of 4.5:4.5:1 by weight. Immobilized spawn were prepared by mixing the pellets from liquid spawn with carriers using a ratio of 1:8 by weight. Within the first 15 days of storage at 20–25 °C, the immobilized spawn grew strongly, respiration intensity and cellulase activities rose rapidly, and the count and brightness of the isozyme bands of esterase, peroxidase, and polyphenol oxidase increased remarkably as well. From days 30 to 60, the cellulase activities fell and the brightness of the peroxidase and polyphenol oxidase bands gradually decreased, whereas the respiration intensity and the band count of esterase and peroxidase remained constant. After 60 days, the cultivated characteristics of the immobilized spawn were same as the fresh conventional solid cottonseed hull spawn. The results showed that immobilized spawn on the basis of the mycelial pellets of liquid spawn adsorbed in carrier can be used to extend the storage time and simplify transportation of liquid spawn of edible mushroom.

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