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Effects of naphthaleneacetic acid (NAA), aminoethoxyvinylglycine (AVG), and sprayable 1-methylcyclopropene (1-MCP) alone or in combination on fruit ethylene production, preharvest fruit drop, fruit quality, and fruit maturation were examined in ‘Delicious’ apples (Malus ×domestica Borkh.). 1-MCP and AVG + NAA, when applied 15 days before anticipated harvest (DBAH) for untreated control trees, more effectively delayed preharvest fruit drop than AVG or NAA used alone. However, there was no significant difference in ethylene production between fruit treated with 1-MCP or AVG + NAA and those treated by AVG. Two applications of NAA increased fruit ethylene production and fruit softening, whereas AVG inhibited NAA-enhanced fruit ethylene production and fruit softening. There was no significant difference in fruit ethylene production, fruit firmness, and fruit drop control between one and two applications of 1-MCP. The concentrations of 1-MCP did not affect the efficacy of 1-MCP when applied 15 DBAH, but high concentration of 1-MCP more effectively delayed preharvest fruit drop than low concentration of 1-MCP when applied 7 DBAH. Both AVG and 1-MCP suppressed expression of 1-aminocyclopropane-1-carboxylate (ACC) synthase gene MdACS1, ACC oxidase gene MdACO1, and polygalacturonase gene MdPG1 in fruit. Expression of ACS5A and MdACO1 but not MdACS1 in fruit abscission zones was decreased by AVG and 1-MCP. 1-MCP more effectively suppressed expression of MdPG2 in fruit abscission zones than AVG alone.
Paeonia ostii ‘Feng Dan’ is an economically important, multipurpose woody plant in terms of its medical, ornamental, and oil values; however, there is a noticeable contradiction between the increasing demands and the lack of excellent germplasm resources because of traditional breeding and propagation approaches. In vitro embryo culture is an attractive option for this issue. This study presents a protocol for in vitro immature embryo culture in P. ostii ‘Feng Dan’, which involves two steps: 1) immature seeds at 30 days after anthesis (DAA) (cellularization stage of endosperm, proembryo stage) or after being cultured in vitro for cotyledon embryo formation (upward micropyle with placenta was the best inoculation method with the highest ratio of seed with cotyledon embryo of 66.67%); and 2) seedling establishment was realized within 7 months via embryo (at 40 DAA or after) germination, shoot induction, rooting, and acclimatization. The multiplication potential was increased with embryo maturity. This protocol provides an available reference for embryo rescue and propagation of tree peony and will be beneficial to shortening the breeding cycle.
The expression of genes for ethylene biosynthesis, ethylene perception, and cell wall degradation in the fruit cortex and fruit abscission zone (FAZ) was examined in relation to preharvest fruit abscission (PFA) and fruit ripening in ‘Golden Delicious’ and ‘Fuji’ apple (Malus ×domestica Borkh.). PFA, fruit ethylene production, and fruit softening increased rapidly during fruit ripening in ‘Golden Delicious’ apples, whereas no PFA, little fruit ethylene, and gradual fruit softening were recorded in ‘Fuji’ apples. The transcript levels of 1-aminocyclopropane-1-carboxylate (ACC) synthase genes, MdACS1, MdACS3, and MdACS5A, increased rapidly in the fruit cortex of ‘Golden Delicious’ apples during ripening, but not in ‘Fuji’ apples. However, only the level of MdACS5A mRNA was up-regulated in the FAZ of ‘Golden Delicious’ apples. The transcript level of ACC oxidase gene, MdACO1, increased in the fruit cortex for both cultivars but increased only in the FAZ of ‘Golden Delicious’ apples. Expression of the ethylene receptor genes, MdETR1, MdETR2, MdERS1, and MdERS2, increased in the fruit cortex for both cultivars, but only MdETR2 and MdERS2 increased in the FAZ of ‘Golden Delicious’ apples. The transcript levels of MdPG2, a polygalacturonase gene (PG), and MdEG1, a β-1,4-glucanase gene, markedly increased only in the FAZ of ‘Golden Delicious’ apples, whereas only MdPG1 rapidly increased in the fruit cortex of ‘Golden Delicious’ apples. Our results suggested that MdACS5A, MdACO1, MdPG2, and MdEG1 in the FAZ might be related to the difference in PFA between these two cultivars, whereas MdACS1 and MdPG1 were associated with fruit softening.
Petroleum-based spills on turfgrass often occur during lawn care maintenance. Damage caused by diesel and hydraulic fluid is particularly difficult to correct. The objective of this study was to compare the effectiveness of combining mulching with remediation for reseeding spilled areas in lawns. Diesel and hydraulic fluid were applied to plots at a rate of 15 L·m−2. Immediately after the spill treatments, two liquid humic amendments and an activated flowable charcoal were applied at a volume rate of 8 L·m−2, respectively, with tap water/dishwashing detergent used as a control. Nitrate nitrogen was added to each remediation treatment to facilitate remediation. The spilled areas were reseeded with perennial ryegrass (Lolium perenne) and then mulched with biochar, peat pellets, and paper pellets, respectively. At 6 weeks after seeding, humic amendment 1 and activated charcoal showed better turf quality than humic amendment 2. Peat pellet mulching presented better turf quality than other mulching methods. Reseeding perennial ryegrass and mulching with peat pellets after remediation with either humic amendment 1 or activated charcoal resulted in acceptable turf quality 6 weeks after diesel and hydraulic fluid spills. Therefore, this reestablishment method is recommended as a practical way to deal with diesel or hydraulic fluid spills in cool-season turfgrasses.
An improved three-stage protocol for plant regeneration via somatic embryogenesis of the horticulturally important plant Iris germanica L. was developed using shoot apex segments as explants. At the first stage of the experiment, 60% of callus was obtained from shoot apex segments of I. germanica on Murashige and Skoog’s (MS) medium supplemented with 4.52 μm 2,4-dichloropheoxyacetic acid (2,4-D) and 0.44 μm 6-benzyladenine (6-BA). When nonembryogenic calli were subcultured on MS medium with 11.31 μm 2,4-D and 0.44 μm 6-BA, maximum frequency of embryogenic callus (66.0%) was obtained. At the second stage, the treatment of 9% (w/v) sucrose resulted in the optimum somatic embryo (SE) formation (70.0%). More than 90.0% of SEs germinated with bipolar structure and regenerated into plantlets on plant growth regulator-(PGR)free MS medium during the third stage. Regenerated plantlets were successfully acclimatized in greenhouse environment with little somaclonal variation. Histological study showed that somatic embryogenesis stages were asynchronous and SEs developed from the surface and inner tissue of embryogenic calli.
Deicing salts often are applied to sidewalks and roadways to enhance pedestrian and driving safety during freezing weather. For example, in eastern North Dakota, average annual snow days and amount are 29 days and 40 inches, respectively. This study was conducted in Fargo, ND, to investigate the population dynamics of turfgrass mixtures composed of kentucky bluegrass [KB (Poa pratensis)], creeping red fescue [RF (Festuca rubra)], and alkaligrass [ALK (Puccinellia sp.)] with the goal of optimizing turf quality by selecting seed ratios containing these species in home lawn mixtures and subject to frequent applications of deicing salts. A total of 21 mixtures were generated based on simplex-lattice design with KB, ALK, and RF contributing to 0%, 20%, 40%, 60%, 80%, and 100% of their respective full-seeding rate of 150, 150, and 300 lb/acre, respectively, after pure live seed (PLS) adjustment. The mixtures were tested at annual deicing salt rates of 0, 160, 320 lb/acre, which represent typical application. The results showed that the botanical component of the stands of grasses shifted over a 2-year period for all salt levels. Despite the good salinity tolerance of ALK reported elsewhere, it did not contribute to the improvement of turf quality in mixtures receiving deicing salts at 320 lb/acre per year. Therefore, ALK is not recommended for lawn, but mixing KB and RF in 48% and 52% of their respective full-seeding rates was recommended for areas adjacent to deicing salt applications.
Low mobility and solubility reduce the availability of traditional phosphorus (P) fertilizer in red acidic soil. Hydroxyapatite (HAP), especially nano-hydroxyapatite (n-HAP), may be more efficient than P fertilizer because of its nanoparticle characteristics. Camellia oleifera (C. oleifera) is an edible oil tree whose productivity is greatly affected by P fertilizer. During this study, we investigated the migration of different particle sizes of HAP (20 nm, 200 nm, and 80 μm) and their effects on the seedling growth of C. oleifera cultivar Huashuo (HS) cuttings. A column experiment showed that the efflux ratio was negatively correlated with particle size in red acidic soil. The leaching results revealed that the contents of total P and available P in the 20-nm treatment were significantly higher than those in the 200-nm and 80-μm treatments in the deep soil (10–15 cm or 15–20 cm), whereas the application of 20-nm n-HAP caused 13.43% wastage of available P. During the container experiments, 200-nm and 20-nm HAP significantly promoted the growth of the seedlings in terms of seedling height, stem diameter, and biomass. The available P contents in the rhizosphere and nonrhizosphere soils were negatively correlated with the HAP particle sizes. In conclusion, the migration of HAP is inversely correlated with particle size, and HAP improves the P bioavailability in red acidic soil. In summary, 200-nm HAP was the best P fertilizer for the seedlings of HS among the three particle sizes. This study offers preliminary results indicating that 200-nm HAP might be a better P fertilizer compared with other two HAP particle sizes for use in future C. oleifera orchards.
The stolon is the main asexual reproductive organ of the medicinal plant Tulipa edulis and has special morphology. In the greenhouse experiment presented herein, the dynamic changes in carbohydrates and related enzymes, proteins, and endogenous hormones of stolons during T. edulis stolon formation were investigated. The results showed that the content of total soluble sugar, sucrose, reducing sugar, fructose, and starch were all significantly enhanced in the middle period when stolon emerged and maintained at relatively high levels until the later period of stolon formation, while protein content decreased during stolon formation. The activities of amylase (AMY), sucrose phosphate synthase (SPS), and sucrose synthase (SS) peaked in the initial period and were negatively correlated with soluble sugars. However, adenosine diphosphoglucose pyrophosphorylase (AGPase) activity increased as stolon formation progressed, and the changes in soluble starch synthase (SSS), granule-bound starch synthase (GBSS) activities presented a single peak, reaching their maximums in the middle period. AGPase, SSS, and GBSS activities were all positively related to starch content. Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) verified the changes in SS and SSS activities via the expression levels of the SS, SSSI, and SSSII genes. The gibberellin (GA) and zeatin riboside (ZR) content attained their maximum in the initial period of stolon formation. Indole-3-acetic acid (IAA) and abscisic acid (ABA) remained at high levels during the initial and middle period and decreased significantly during the later period of stolon formation, inversely to the ratio of ABA:IAA. Analysis of the physiological changes in T. edulis stolon indicated that the accumulation of soluble sugars and starch via various enzymes, a high level of IAA and a low ABA to IAA ratio mainly contributed to stolon development of T. edulis. This paper explored carbohydrate levels and endogenous hormones profiles during stolon formation, which provided the theory basis for further regulating stolon growth of T. edulis.
The responses of photosynthesis, chlorophyll fluorescence, and de-epoxidation state of the xanthophyll cycle pigments (DEPS) of micropropagated apple trees (Malus ×domestica) were investigated under whole-root water stress (WRS) and half-root water stress (HRS) induced by polyethylene glycol 6000 to simulate whole and partial root zone drying. Compared with control plants without water stress, plants under WRS and HRS exhibited reduced leaf net photosynthetic rate (Pn) and stomatal conductance (g S) with a greater reduction in WRS than in HRS plants. However, intercellular CO2 concentration (Ci) increased under WRS as water stress was prolonged, signifying a non-stomatal limitation of Pn. Regarding HRS, decreased Pn was mainly the result of a stomatal limitation explained by a relatively low Ci. Changes in photosynthesis and chlorophyll parameters indicate that severe and slight damage occurred to the photosynthetic apparatus of WRS and HRS leaves, respectively, starting at Day 3 after initiating water stress. This damage was not evident on the donor side but was expressed as a reduced capacity of the acceptor side of the photosystem II reaction centers. To prevent damage from excess light, the DEPS of WRS leaf increased. Decreased g S could explain reduced water use under an irrigation strategy of partial root zone drying in fruit trees.
The mechanism regulating procyanidin (PA) accumulation in banana (Musa acuminata) fruit is not understood. During this study, the effects of PA treatment on the activities of banana PA biosynthetic enzymes and transcriptomic profiles were investigated. The results showed that PA treatment delayed the decreases in leucoanthocyanidin reductase and anthocyanidin reductase activities, which affected the accumulation of PA. Furthermore, the peel samples of the control fruit and the PA-treated fruit on day 1 were selected for transcriptomic analysis. The results revealed that PA treatment induced 1086 differentially expressed genes. Twenty-one key genes, including those encoding biosynthetic enzymes and regulatory factors involved in PA biosynthesis, were validated using a quantitative real-time polymerase chain reaction. The results showed that these genes were upregulated by PA treatment during banana storage. Taken together, our study improves current understanding of the mechanism underlying PA-regulated banana senescence and provide new clues for investigating specific gene functions.