`McIntosh' apples (Malus ×domestica Borkh.) display a rapid increase in ethylene production as they ripen, resulting in more preharvest drop and accelerated softening compared with other major cultivars. Economic considerations often dictate a choice between delaying harvest to achieve color development or harvesting earlier to avoid excessive fruit softening and drop. We have evaluated the effects of plant growth regulators (PGRs) and summer pruning on this balance. Treatments were applied to trees in the Mid-Hudson region in New York state in 1995 and 1996, and a subset of treatments was applied in the Champlain Valley region in 1996. NAA, applied at 10 mg·L-1 in 1995 and 20 mg·L-1 in 1996, reduced drop on only one sample date in only one of the three trials. Ethephon at 150 mg·L-1 plus 10 mg·L-1 NAA, accelerated ripening and permitted harvest before substantial drop occurred. However, earlier harvest resulted in smaller fruit size, and if ethephon-treated fruit were not picked within a narrow window, rapid drop ensued, and fruit developed a high senescent breakdown incidence during storage. ReTain, containing AVG, at 124 g·ha-1 a.i. delayed drop in all three trials, but its use resulted in firmer fruit after storage in only two of seven comparisons. Use of ethephon on AVG-treated trees enhanced red color but accelerated drop, although it was reduced less than when ethephon was used alone. Severe late summer pruning accelerated red color development, drop and ripening in both years of the study. AVG was more effective for management of `McIntosh' harvest in the cooler Champlain Valley region than in the Mid-Hudson Valley region. Chemical names used: naphthalene acetic acid (NAA); 2-chloroethylphosphonic acid (ethephon); aminoethoxyvinylglycine (AVG).
Effects of early spring cultural practices and microclimate manipulation on `Jewel' strawberry (Fragaria ×ananassa Duch.) plant development, carbohydrate reserves, and productivity were measured in the field and under simulated early spring conditions in growth chambers. With traditional winter straw mulching practices of the northeastern and midwestern United States, starch content of overwintering leaves, crowns, and roots in the field declined by 51%, 78% and 69%, respectively, during late winter and early spring. There was also a net loss in root biomass over winter and no new leaf growth before mid-April, suggesting that carbohydrate reserves could be limiting plant performance during the critical early growth and flowering phase in spring. In growth chambers, exposure to CO2 levels between 700 to 1000 mL·L-1 significantly increased photosynthetic rates of overwintering and spring leaves compared to ambient CO2 levels. Elevated CO2 in growth chambers also accelerated flower development, reduced depletion of starch reserves in roots, and increased starch accumulation in crowns. In the field, early removal of straw and application of spunbonded rowcover accelerated plant development, increased starch accumulation in the leaves, and increased photosynthetic rates of overwintering and spring leaves. Elevating the CO2 levels under rowcover further increased photosynthetic rates and advanced plant development and starch accumulation, but not significantly above rowcover alone. Carbohydrate losses later in the season during flower development were reduced when rowcover was applied in early spring. Total fruit yield was as much as 48% higher for plants under rowcover in early spring than those that had no cover and an additional 9% higher when CO2 was elevated. Yield improvements were attributed mostly to an increase in the number of marketable secondary and tertiary fruit than to an increase in mean fruit size. The economics of rowcover use is favorable if the material is reused. The added expense of CO2 gas and the resulting marginal gains would not make field CO2 enrichment an economically viable practice for strawberry growers using the method herein.
Abstract
Twenty species of ornamental trees were grown for 12-16 months in 50 cm diameter (“20 gallon”) containers. Six individuals of each species were irrigated with tap water from a public potable water supply and 6 with secondary treated sewage effluent from a wastewater treatment facility. Three individuals within each irrigation treatment received controlled-release fertilizer applications and 3 received no supplemental fertilization. The effluent irrigation significantly accelerated growth in 4 species: orchid tree (Bauhinia variegata L.), baldcypress (Taxodium distichum (L.) L. Rich), coconut palm (Cocos nucifera L.), and black iron wood (Krugiodendron ferreum [Vahl] Urban). The addition of supplemental fertilization accelerated growth in 7 species: orchid tree, ficus (Ficus benjamina L.), black olive (Bucida buceras L.), satin leaf (Chrysophyllum oliviforme L.), royal poinciana (Delonix regia [Bojer] Raf.), silver buttonwood (Conocarpus erectus var. sericeus Fors. ex DC.), and blolly (Pisonia discolor Spreng.). A significant interaction occurred between irrigation and fertilization in 3 species: orchid tree, red cedar (Juniperus silicicola [Small] L. H. Bailey), and lignum vitae (Guaicum sanctum L.). The remaining 8 species grew at rates that were not significantly influenced, one way or another, by either source of irrigation or supplemental fertilization.
We previously reported that growth of lisianthus [Eustoma grandiflorum (Raf.) Shinn.] seedlings is accelerated by amending the growing medium with 1% (w/w) chitosan. This finding prompted us to search for organic nitrogenous other substances like chitosan which could accelerate seedling growth. Seeds of E. grandiflorum `Peter blue line 2'were sown in a sandy loam growing medium containing 1% (w/w) chitosan, tryptone, casein, collagen or gelatin. At eleven weeks after sowing, leaf length and width, fresh and dry weights of the shoots and roots of twelve plants were determined for each treatment. Eleven weeks after sowing, the leaves at the fifth node had expanded in the chitosan, tryptone and collagen treatments while the leaves of the third node had not yet expanded in control plants. Fresh and dry weights of shoots and roots were significantly greater for plants grown in media amended with chitosan or tryptone. Percent nitrogen (N) and potassium (K) in the shoots and roots and percent phosphorus (P) in the shoots was greater only in the N side dressing treatment. The nitrate nitrogen (NO3-N) concentration was significantly greater in media amended with tryptone or collagen compared to the other treatments.
Abstract
The influence of photoperiod, supplemental lighting, and pinching method on the growth and flowering time of Pentas lanceolata Benth. cultivated as a pot crop was determined. Pentas is a quantitative long-day plant (LDP). Plants given long days (LD) flowered 7 to 10 days earlier than those that received short days (SD). Light was supplemented during daylight hours only to distinguish from photoperiodic effect and 6 weeks of HID (640 ± 30 µmol·s–1·m–2) supplemental light also accelerated flowering. Height was retarded with chlormequat, but daminozide and ancymidol were ineffective. No growth regulator affected flowering time. Pinching delayed flowering time but increased the number of blooms per plant. Pinching to three nodes was more beneficial and resulted in faster flowering than pinching to one node. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium (chlormequat); butanedioic acid mono (2,2-dimethylhydrazide (daminozide); α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol).
Dense-flowered loosestrife is a quantitative long-day (LD) plant. Plants given a LD photoperiod (16 hours) flowered 21 and 34 days earlier than plants given 12- and 8-hour photoperiods, respectively. Plants under LDs produced significantly more flowers than those under 8- and 12-hour photoperiods. Only 1 week of LD was needed for 100% flowering; however, optimum flower count and size were produced with 3 weeks of LD. Plant dry weight did not differ significantly among treatments; however, LDs produced fewer but larger leaves, particularly those subtending the inflorescence. Total plant growth increased as temperature increased, but lower temperature (10C) decreased flower initiation and prevented flower development. High temperature (26C) reduced the persistence of open flowers. The optimum temperature for dense-flowered loosestrife growth was ≈20C. Flowering was accelerated and dry weight production increased as irradiance levels increased from 100 to 300 μmol·m–2·s–1.
The influence of water-soluble fertilizer (WSF, 3 different formulations) and slow-release fertilizer (SRF, Osmocote, 14N-6.2P-11.6K) on the growth and quality of potted carnation (Dianthus caryophyllus cv. Invitation) in a C-channel mat irrigation system was investigated. When fertilized with 0.4, 0.8, or 2.0 g·L-1 of WSF (20N-7.9P-16.6K for weeks 1-4, 13K-0.1P-18.8K for weeks 5-11, and 15N-0P-12.5K for weeks 12-15), the 0.8 g·L-1 solution produced the highest quality plants as determined by total shoot fresh and dry weights, leaf area and number, plant height, and number of branches per pot. The quality of plants grown with 0.4 g·L-1 or 2.0 g·L-1 WSF solution was also commercially acceptable. The growth rate of all plants began to accelerate at around 60 days after treatment started, with some variation with the fertilizer treatments. Plants began to show a reduced growth rate at around 90 days from the treatment when they underwent a phase change from vegetative growth to reproductive growth. Plants grown with SRF alone were less vigorous than those grown with WSF, especially when temperature was lower. Results of this study indicate that high quality pot carnations can be produced, using a reduced amount of fertilizer applied to the C-channel mat irrigation system.
Trinexapac-ethyl (TE) [4-(cyclopropyl-a-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] effects on turfgrass root architecture are not known. It has been postulated that PGR application could cause photoassimilate that is normally used for shoot growth to be funneled to root growth. This study evaluated the effects of a single TE application on kentucky bluegrass (KBG) root and shoot growth for seven weeks. Individual KBG plants were grown in a hydroponic system and harvested weekly. At each harvest, tiller height, tiller number, and color ratings were recorded. Estimates of total root length (TRL), root surface area (SA), and average root diameter were measured using the WinRhizo system. Trinexapac-ethyl reduced plant height for 4 weeks followed by a period of postinhibition growth enhancement. Trinexapac-ethyl increased tiller number over the course of the study and slightly enhanced plant color. Trinexapac-ethyl reduced TRL and SA 48% and 46% at 1 week after treatment (WAT) followed by an accelerated growth rate 1 to 4 WAT. Trinexapac-ethyl had no effect on root diameter. On a tiller basis, TE initially reduced TRL and SA 30% and 31%, respectively. Total root length per tiller and root surface area per tiller were reduced by TE treatment, but by 7 WAT, those differences were no longer significant. Initial reductions in TRL and SA per tiller may reduce tiller competitiveness for water and nutrients. Based on data for TRL and SA per tiller, shoot and root growth must be considered in total to fully understand TE effects on plant growth. Field research is needed to corroborate results from hydroponic-studies and examine the effect of various TE rates and multiple applications on turfgrass root and shoot growth.
The effect of bulb storage and forcing temperatures on growth, flowering, and inflorescence development and the death of inflorescence (blast) of Lachenalia aloides Engl., `Pearsonii' was investigated. Following development of about 5 florets, bulbs were stored at 10, 12.5, 15, 20, and 25 °C for 15, 30, or 45 days and forced in greenhouses at 17/15 °C and 21/19 °C. Flowering was accelerated, and leaf length and floret number were reduced, when bulbs were stored at 10, 12.5, or 15 °C for 45 days compared to storing at 20 or 25 °C. Flowering was further accelerated by forcing at 17/15 °C compared to 21/19 °C. When bulbs were stored at 10, 15, 20, or 25 °C for 4 weeks and grown in greenhouses at 17/15 °C, 21/19 °C, 25/23 °C, and 29/27 °C, the incidence of inflorescence blast was increased when bulbs were stored at 10 and 15 °C and forced at 25/23 °C compared to low temperatures. Bulbs were forced in greenhouses maintained at 18/16 °C, 22/20 °C, or 26/24 °C for 12 weeks. During forcing, plants were subjected to constant or alternating forcing temperatures at 4-week intervals. Inflorescence blast occurred when the temperature was 26/24°C during the first 4 weeks after potting. Storing Lachenalia bulbs at 10° to 15 °C before potting then forcing at 17/15 °C accelerated flowering and produced quality plants with short leaves and floral stems. Inflorescence development during bulb 10 °C treatment and inflorescence blast that occurred after only 3 days of 35 °C was demonstrated using scanning electron microscopy and magnetic resonance imaging techniques.
This study was designed to compare and determine root growth and nutritional responses of creeping bentgrass cultivars that differ in heat tolerance to deferential, supraoptimal shoot and root temperatures. Shoots and roots of `Penncross' (heat sensitive) and `L-93' (heat tolerant) were exposed to four differential air/soil temperature regimes (20/20-control, 20/35, 35/20, and 35/35 °C) in water baths and growth chambers. Exposing roots to supraoptimal root temperature (35 °C) while maintaining shoots at normal temperature (20 °C), or at 35 °C in particular, reduced root fresh weight, root number, the content of N, P, and K in shoots and roots, and accelerated root death for both cultivars. High root temperature had a greater detrimental effects on root growth and nutrient accumulation than high shoot temperature for both cultivars. Reducing root temperature at supraoptimal shoot temperature improved root growth, reduced root mortality, and increased N, P, and K content in shoots and roots. Among the three nutrient elements, K was the most sensitive to changes in root temperature. L-93 generally maintained higher root fresh weight and number, and N, P, K content in shoots and roots, particularly K in roots, under high root (20/35 °C) or shoot/root (35/35 °C) temperatures. The results indicated that root growth and nutrient accumulation, particularly K, played an important role in creeping bentgrass tolerance to heat stress imposed to shoots by high air temperature or to roots by high soil temperatures. Reducing root temperature under supraoptimal ambient temperatures enhanced root growth and nutrient relations, and thus could lead to the improved shoot growth in cool-season grasses as reported previously.