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Abstract
An automated, mechanical oscillatory shaking (AMOS) device was developed and tested for its ability to control height of chrysanthemum (Chrysanthemum morifolium Ramat) cvs. May Shoesmith, Yellow Fuji Mefo, Improved Mefo, and Dramatic. The AMOS device permits automatic and uniform administration of shaking stress to a number of plants simultaneously. Shoot height and fresh weight were effectively reduced by shaking treatment consisting of 160 to 220 cycles per minute for 4 minutes daily at 0800 hours with ‘Dramatic’ exhibiting the greatest dwarfing response. The fresh weight of all 4 cultivars was reduced to an equivalent extent by 28 days of this combined vibrational-contact treatment.
Abstract
Elongation growth of Chrysanthemum morifolium Ramat. cv. May Shoesmith was inhibited by daily shaking with an automated mechanical device. The dwarfing effect was more pronounced if plants were shaken at 0800 than at 1600 or 2400 hours. The longer the duration of stress, the greater the growth inhibition. Thirty seconds to 2 minutes of stress per day were required for significant dwarfing, with saturation of the effect at 4 to 5 minutes. Four-minute treatments 2 to 4 times daily maximized the stress response. Node number, fresh weight, and dry weight were reduced by shaking, but dry-to-fresh weight ratio was increased. Reciprocity applied to the stress responses in that one 4-minute stress per day had the same growth-retarding effect as four 1-minute stresses. Shaking did not significantly affect flower bud initiation, flower size, or floral keeping quality.
Furrow irrigation of peppermint (Mentha piperita L.) has certain benefits over sprinkler irrigation, but usually wastes irrigation water. Alternate-furrow irrigation allows frequent application of small amounts of water, which is an advantage over conventional furrow irrigation. In a variation of alternate-furrow irrigation, alternating-furrow irrigation, every other furrow is irrigated at the first irrigation, and the remainder at the second, then this procedure is repeated throughout the season. It is a low-cost, low-energy alternative to sprinkler and center pivot irrigation systems. Our objective was to compare yield and water use of alternating-furrow irrigation with those of conventional every-furrow irrigation for peppermint. Field experiments in 1992 and 1993 indicated that the soil water content was adequate under both irrigation treatments, and the water savings for alternating-furrow irrigation were attributed to less runoff and less evaporation from the soil surface. There was no difference in yield between the systems, although alternating-furrow irrigation required about half of the water applied with the conventional treatment. One limitation of alternating-furrow irrigation occurred near the end of the growing season, when the plants lodged, partially dammed the furrow streams, and made timely furrow advance difficult. This problem was resolved by irrigating every furrow after lodging occurred.
Rice (Oryza sativa L.) is a candidate crop for use in Controlled Ecological Life-support Systems (CELSS) proposed for a lunar or Mars outpost. `Ai-Nan-Tsao' is a promising semi-dwarf cultivar because growth volume is limited and HI (percent edible biomass) is high. Yield efficiency rate (YER: g grain/m3 per day [g nonedible biomass]-) combines edible yield rate (EYR: g grain/m3 per day) and HI to quantify edible yield in terms of penalties for growth volume, cropping time, and nonedible biomass production. Greenhouse studies indicate EYR increases with plant density from 70 to 282 plants/m2. YER and shoot HI are stable across this density range because nonedible biomass accumulation keeps pace with edible. Tiller number and panicle size per plant decreased with increasing plant density, but total tiller and panicle number per unit area increased to compensate. Density trials in rigorously controlled environments will determine if higher plant densities will produce even greater YER. This research is supported by NASA grant NAGW-2329.
Mineral resources will be recycled in a controlled ecological life-support system (CELSS) deployed in space. N typically is supplied to crops as
Due to its short time to flower (14-18 days) and rapid maturation cycle (50-55 days), dwarf rapid-cycling brassica (Brassica napus) is under consideration as a candidate oilseed crop for NASA's Controlled Ecological Life Support Systems program. Recent work has focused on defining a set of optimum environmental conditions which permit increased crop yield in terms of g·m-2d-1 of edible biomass. A wide range of environmental variables have been considered including lamp type, CO2 level, nutrient solution pH, and planting density. In addition, nitrogen nutrition regimes have been manipulated with respect to nitrogen concentration (2 to 30 mM), source (NH4 + and/or NO3 -), and time of stepwise changes in nitrogen level (day 14 to 28). The highest seed oil content (42% DW basis) has been found under limiting nitrogen levels (2 mM). However, the low nitrogen inhibits overall seed production potential. Different cultural techniques also have been compared, including solid-substrate, passive wicking hydroponics versus liquid culture systems. Trials are underway to assess crop growth and development under the “best set” scenario of environmental conditions. At present, the highest seed yield (10.6 g·m-2d-1) has been obtained using solid-substrate hydroponic systems under a combination of metal halide and high-pressure sodium lamps. Constant CO2 enrichment to 1000 μmol·mol-1 did not increase crop yield rate.
Research supported in part by NASA grant NAGW - 2329.
Fall application of 2-chloroethylphosphoric acid (ethephon) is known to delay spring budbreak in peach (Prunus persica). To study seasonal variation in peach response to dormancy-breaking plant bioregulators and their possible interaction with ethylene, peach shoots were cut in the field at various intervals during endodormancy. Shoots were dipped in the dormancy-breaking bioregulators hydrogen cyanamide (H2CN2, 100 mM) or gibberellic acid (KGA3, 130 μm), alone or in combination with 1.38 mM ethephon. Treated shoots were held in beakers of either tap water or 1 mM silver thiosulfate (STS), and placed in growth chambers with potassium permanganate traps, 12/12 h photoperiods and 21/26 C temperature regimes. Dormancy-breaking efficacy (apical budbreak at 21 days) of both bioregulators increased as endodormancy progressed. At all intervals, H2CN2, broke dormancy more effectively than KGA3. The addition of ethephon to H2CN2 application prior to any CU accumulation (20 Oct) had no effect on efficacy (80% budbreak), but its addition after accumulation of ∼50 CU (8 Nov) or ∼320 CU (14 Dec) reduced subsequent budbreak to 25% and 40%, respectively. The addition of ethephon to KGA3 applications reduced budbreak both prior to (27 Oct) and after (8 Nov) initial CU accumulation. STS in the beaker solution increased both the extent (27 Oct) and the rate (14 Dec) of KGA-induced budbreak The interaction of ethylene, bioregulator type, and endodormancy regulation will be discussed.
Abstract
Scald was the major grade lowering defect resulting from mechanical harvesting of sour cherries for processing. Histological sections of scalded tissue showed no crushing or distortion of cells, but the epidermal cells appeared dense and the cell walls appeared to be thicker than those of nonscalded tissue. Since the cells of scalded tissue did not appear distorted, bruising apparently induced a chemical change as a result of membrane disruption bringing about discoloration. Microscopic examination indicated that darkened bruises on the epidermis of the cherries occurred prior to mechanical harvesting. Tannins were located primarily in the epidermal region, but during a 24-hour soak there was a slight movement of tannin into the outer cortical cells. Greater movement occurred in mechanically harvested cherries than in handpicked fruit. The cellular disruption resulting from bruising by mechanical harvesting possibly aided the movement of tannins. Scald was a major grade lowering factor when mechanically harvested cherries were soaked longer than 8 hours before processing.
Abstract
Seedlings of tomato (Lycopersicon esculentum Mill. cv. Rutgers) were agitated periodically on a gyratory shaker. Shaking plants at 175 rpm for 5 minutes once daily during the winter reduced leaf area, stem length, and water content and dry weight of both leaves and stems. This treatment was ineffective when applied during the summer. Five- to 20-minute treatments applied 2 or 3 times daily reduced growth during either season, but were more effective during winter. Responses were independent of the time of day at which treatment took place. Leaf area, stem length, water content of leaves and stems, leaf dry weight, and specific stem water content were reduced progressively relative to undisturbed controls as the shaking rate increased from 125 to 175 rpm during the winter. Leaf area, specific leaf water content, and specific stem water content were reduced by shaking at 44% of full summer sunlight, but not at 31% or 17%. Shaking enhanced specific stem weight only at 44% light, whereas stem length was reduced most by shaking at 17% light. Differences in relative plant response to shaking between summer and winter remained even when seasonal differences in solar flux density were minimized by use of shadecloth during the summer.
Abstract
Low ambient humidity reduced growth and increased H2O consumption by seedlings of tomato (Lycopersicon esculentum Mill. cv. Kokomo) grown in well-watered peat pellets. Shielding the root medium with a thin, flexible plastic sleeve prevented growth reduction, which appeared to be largely the result of root zone evaporative cooling. Low inlet relative humidity (5%) depressed root temperature of unjacked peat pellets –7° to –9°C. Root zone shielding reduced the temperature depressions of both humidity treatments to –4°. Of various growth parameters observed, root growth was most dramatically improved by shielding at either level of humidity.