Search Results
Abstract
Growth of 2-year-old tart cherry (Prunus cerasus L.) trees as measured by trunk circumference increase or total shoot elongation was significantly greater in plots receiving chemical or mechanical weed control within the tree row than in plots receiving between-row cultivation only. Shoot growth of one-year-old apple (Malus domestica Borkh. ‘Delicious’) trees responded similarly to weed control. Tart cherry trees in hand weeded and dinoseb or glyphosate treated plots had greater growth than those in paraquat treated plots. Tart cherry trees in plots receiving chemical or mechanical weed control out-yielded trees in unweeded plots during the first year of production. ‘Delicious’ apple trees in plots treated with dinoseb (6.7 and 10.1 kg/ha), the high rate of glyphosate (1.7 kg/ha), or mechanical weed control also outyielded trees in unweeded plots during the first year of production. Effects of weed control on growth and yield were less distinct during the 2nd year of production. Trees from treated plots came into production one year earlier than trees in the unweeded plots. Chemical names used: 2-(1-methylpropyl)-4,6-dinitrophenol (dinoseb); N-(phosphonomethyl)glycine (glyphosate); 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat).
Petioles were gathered at three times during the season: bloom, veraison, and harvest, in two trials `Chardonnay' (Ch) and `Cabernet Sauvignon' (CS). In each trial, scions were grafted onto 14 rootstocks. Petioles were analyzed for NO3-nitrogen, %N, and %K. Averaged over rootstocks, CH petiole NO3 levels were highest at harvest and lower at both bloom and veraison. A similar trend was seen in `Cabernet Sauvignon', although, on average, NO3 levels were higher on all sampling dates. In Ch, the rootstocks `Ramsey', `St George', and `110R' were among the highest in NO3, while Harmony and 1616C were among the lowest. In CS, O39-16 was among the highest in NO3, while 44-53M was among the lowest. In both cultivars and among all rootstocks, petiole NO3 was positively correlated with petiole %N in Ch, petiole K declined throughout the year, while in CS most rootstocks were relatively stable. In Ch, the rootstocks `Harmony', `1616C', and `44-53M' had high levels of K, while in CS `44-53M' was among the highest.
Abstract
Tomato plants (Lycopersicon esculentum Mill. ‘US 28’) and plant parts ranging in fresh weight from 6 mg to 180 g were frozen in the presence and absence of epiphytic ice nucleation active (INA) bacteria. As weight increased, freezing temperatures rose from —10.5° to — 2°C in the absence of INA bacteria but varied from —3° to —2° in inoculated samples. The freezing behavior of entire plants could only be estimated using small plant parts when INA bacteria were present. INA bacteria were detected by a plate harvesting method. The fraction of tomato stem sections frozen increased with increasing exposure duration at constant temperature.
Abstract
Flower yields from October to May increased with the duration of supplementary lighting. Lighting improved flower yields by increasing bottom breaks, stimulating axillary shoot development after flower removal, and slightly reducing the days from cut-to-cut. Development of additional axillary buds was the principal factor in the improved branching of lighted plants. Excessive plant branching from supplementary lighting during a 7-month flowering period reduced significantly flower stem length, node number, and fresh wt of cvs. Shocking Pink and Red American Beauty. The 6.2 w/ft2 of incandescent light after the high intensity lighting period improved the flower quality of ‘Forever Yours’ but not of ‘Red American Beauty’. Plants lighted 9, 12, or 21 hr daily had fewer blind stems than unlighted plants.
Abstract
Stock plants of Chrysanthemum morifolium Ramat. cv. ‘Bright Golden Anne’ lighted continuously from September 30 to May 15 with Multivapor and Lucalox lamps (100 W/m2) produced more cuttings than those receiving only seasonal daylight and photoperiod lighting. High intensity supplementary lighting improved cutting quality by increased fresh and dry weight and stem diameter. Cuttings from plants receiving high intensity lighting rooted in fewer days, had greater root fresh and dry weights, and greater top fresh weight than plants lighted photoperiodically. After transplanting, the cuttings given high intensity light became established more rapidly and developed into flowering plants of higher quality.
Abstract
No relationship was observed between the population of ice nucleation active (INA) bacteria and the temperature at which ice formed in peach [Prunus persica (L.) Batsch] shoots. The ice nucleation temperature remained stable throughout the year, even during periods when INA bacteria were not detected. An intrinsic ice nucleating substance seemed to be responsible for initiating ice formation and limited supercooling to about —2°C. The ice nucleating agent seemed to be a constitutive component of mature wood and was stable under a range of chemical treatments. Ice nucleation was influenced by sample mass, temperature, and length of exposure. The freezing behavior of peach shoots was best described using a stochastic model of ice nucleation.
Abstract
Experiments were conducted to determine the relative contributions of bacterial and nonbacterial ice nuclei to freezing of peach [Prunus persica (L.) Batsch] shoots. Exposure to 33°C for 3 hr eliminated bacterial ice nuclei active at −3° on inoculated shoot pieces, but controls were not affected. In another experiment, ice nucleation temperatures and ice nucleation-active (INA) bacterial populations of field-collected shoots were determined. Mean freezing temperatures of 20 g (fresh weight) shoots were not significantly different in the presence or absence of INA bacteria (detection limit of 10 cells/g fresh weight). INA bacteria were detected on 19% of the shoots with a maximum natural population of 180 cells/g fresh weight. Inoculation studies indicated that 20 g fresh weight peach shoots contained a mean of 1.0 nonbacterial (−3°) ice nuclei, while shoots with 180 INA cells/g fresh weight averaged 1.4 (−3°) ice nuclei per 20 g. Most ice nuclei active at −3° were of nonbacterial origin.
Cold acclimation (CA) of `Midiron' and `Tifgreen' turf bermudagrasses (Cynodon dactylon L. Pers. × C. transvaalensis Burtt-Davy) induced tolerance to lower freezing temperatures and altered protein synthesis in crowns. LT50 (lethal temperature for 50% of plants) values were lowered ≈5C after 4 weeks in controlled-environment chambers under CA [8/2C (day/night) cycles with a 10-hour photoperiod] vs. non-CA (28/24C) conditions. LT50 values for `Midiron' plants decreased from -6.5 to -11.3C after CA and from -3.6 to -8.5C for `Tifgreen'. Proteins synthesized by isolated crowns were radiolabeled in vivo for 16 hours with 35 S-methionine and 35 S-cysteine. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography revealed increased synthesis of several cold-regulated (COR) proteins in CA crowns of both cultivars. Synthesis of intermediate molecular weight (MW) (32 to 37 kDa) and low-MW (20 to 26 kDa) COR proteins was greater in `Midiron' than `Tifgreen' crowns.
Isoenzyme staining of horizontal starch gels was used to characterize 23 cultivars and three advanced selections of red raspberry (Rubus idaeus L.). The genotypes were separable using the enzymes malate dehydrogenase, phosphoglucoisomerase, phosphoglucomutase, and triose phosphate isomerase. In addition, staining for isocitrate dehydrogenase and shikimate dehydrogenase revealed polymorphisms in some cultivars. By combining these results with those obtained for 78 previously tested cultivars, 75 of the 104 (72%) genotypes tested were uniquely characterized using the six isoenzymes.