The effects of hydrogen cyanamide (H2CN2) sprays on vegetative and reproductive bud growth and development were evaluated for `Climax' rabbiteye (Vaccinium ashei Reade) and `Misty' southern highbush blueberry (V. corymbosum L. hybrid). `Climax' plants were sprayed with 0% or 1% H2CN2 (v/v) at each of several time intervals or flower bud growth stages following either 270 or 600 hours of artificial chilling. `Misty' plants were sprayed with 0%, 1%, or 2% H2CN2 (v/v) immediately after exposure to 0, 150, or 300 hours of artificial chilling. H2CN2 application to `Climax' plants at 3 days after forcing (DAF) and at 10% to 30% stage 3 flower bud development dramatically accelerated leafing, and only minimal flower bud damage was observed at these application times. For `Misty', vegetative budbreak was increased and advanced by both H2CN2 spray concentrations, regardless of pretreatment chilling levels; the number of vegetative budbreaks per plant increased with increased concentration. Timing of anthesis did not appear to be affected by H2CN2, but fruit maturity was hastened. Increased pretreatment chilling also hastened fruit development. This effect on maturity appears to be due primarily to increased and accelerated vegetative budbreak, which probably increased leaf: fruit ratios. Greater flower bud mortality from H2CN2 occurred in nonchilled plants than in those chilled for 150 or 300 hours, especially at 2% H2CN2. These results indicate that H2CN2 has potential value in stimulating vegetative bud development, which potentially hastens maturity in blueberries grown under the mild winter conditions of the Southeast. However, spray concentration and timing of application will be critical to successful use of this compound.
Foliar application of 500 or 1000 mg BA or PBA/liter to stock plants of golden pothos [Epipremnum aureum (Linden & Andre) Bunt.] induced axillary bud elongation but did not promote growth of cuttings taken from these stock plants. Cuttings from plants treated with BA + GA4+7, each at 1000 mg·liter-1, died. Plants grown under 1000 μmol·s-1·m-2 had more but smaller leaves than those under 420 μmol·s-1·m-2. Cuttings produced under the higher light level grew more rapidly. Leaf area increased while stem length decreased as Osmocote slow-release fertilizer (18N-2.6P-10K) increased from 4 to 16 kg·m-3. A 24N-3.5P-13.3K water-soluble fertilizer applied at the rate of 0.42 g/500 ml weekly produced the best plants and resulted in the best cutting growth. Cuttings taken from stock plants receiving Osmocote at 4 kg·m-3 grew slower than those produced at other rates. Placement of cuttings in a mist-propagation bed for 1 or more weeks resulted in an accelerated growth rate relative to nonmisted cuttings. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (PBA); (1α,2β,4aα,10β) 2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-1,10-dicarboxylic acid l,-4a-lactone (GA4+7).
98 ORAL SESSION 21 (Abstr. 532–539) Cross-commodity: Postharvest Metabolism/Plant Growth Regulators
We examined effects of single-layer glass and double-layer antifog polyethylene films on growth and flowering of stock (Matthiola incana L.) and snapdragon (Antirrhinum majalis L.) in a 3-year period. Stock produced more buds/spike with shorter but thicker stems under single-layer glass and under antifog 3-year polyethylene, and showed higher photosynthetic capacity (P c) under single-layer glass than under other covers regardless of light regimes. Similarly, growth and flowering of snapdragon were significantly better under single-layer glass than in polyethylene houses. A supplemental light of 60 μmol·m-2·s-1 accelerated flowering by 20 to 25 days, improved flower quality, and eliminated differences in plant growth and quality of snapdragon between covering treatments. The P c of stock was lower under all polyethylene covers than under single-layer glass. Among the three antifog polyethylene films, a slightly higher P c was measured for plants under antifog 3-year polyethylene. However, there was no difference among covering treatments in the net photosynthetic rate (P N) at low light level (canopy level). Supplemental lighting reduced P c of stock leaves, especially under single-layer glass, and diminished differences in P c among covering treatments. Dry mass was more influenced by larger leaf area caused by higher leaf temperature than by P N. Overall, antifog 3-year polyethylene was a good covering material when both plant quality and energy saving were considered.
To study the reasons for the losses of rooted semihardwood cuttings of olive propagated under the mist method, a 2-year experiment was carried out at the Horticulture Dept. of Faculty of Agriculture of the Tehran Univ. In this experiment, semihardwood cuttings of olive (Zard cultivar) in four different media—heavy-(Al), semi-heavy(A2), medium (A3), and light (A4), all disinfected with two different concentrations of Captan—were used. Root growth stages with low, medium, and light densities in spring and fall were evaluated. The results indicate that there are the least losses in semi-heavy (A2) and medium (A3) media. This could be the result of a better ventilation conditions in these media, which activates N and Ca and finally accelerates the better growth conditions in all young rooted cuttings. On the other hand, it was clear that inadequate disinfection will result in losses of rooted cuttings, and using Captan at 2 ppm gives the best result. This research indicate that, with the higher growth rate, the first medium will have the fewer losses. The reason is the higher density and more durability and strength of the root, which control the disease-causing factors; so far that these factors do not influence the young roots. Finally, strong and dense roots show less losses. This experiment was designed in a factorial with randomized complete block and the averages were compared in a Duncan test and the results of abnormally distributed characteristics were shown by using logarithmic and sinus method.
This experiment was initiated to determine the effects of supplementary lighting of 100 μmol·s-1·m-2 (PAR) in combination with four N rates (100, 200, 300, and 400 mg N/liter) on growth of celery (Apium graveolens L.), lettuce (Luctuca sativa L.), broccoli (Brassica oleracea italica L.), and tomato (Lycopersicon esculentum Mill.) transplants in multicellular trays. Supplementary lighting, as compared with natural light alone, increased shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 22%, 40%, 19%, and 24%, and root dry weight by 97%, 42%, 38%, and 21%, respectively. It also increased the percentage of shoot dry matter of broccoli and tomato, leaf area of lettuce and broccoli, and root: shoot dry weight ratio (RSDWR) of celery and broccoli. Compared with 100 mg N/liter, a N rate of 400 mg·liter-1 increased the shoot dry weight of celery, lettuce, broccoli, and tomato transplants by 37%, 38%, 61%, and 38%, respectively. High N fertilization accelerated shoot growth at the expense of root growth, except for tomato where a 16% increase of root dry weight was observed. High N also reduced percentage of shoot dry matter. Supplementary lighting appears to be a promising technique when used in combination with high N rates to improve the production of high quality transplants, particularly those sown early.
Abstract
The growth of paper birch (Betula papyrifera Marsh.) seedlings was greatly accelerated by high light intensity applied in a growth chamber at the cotyledon stage and continued for the next 8 weeks. At the end of the 8-week period, seedlings grown in a growth chamber under 2500 ft-c (26.9 klx) of cool-white fluorescent and supplemental incandescent light, a 16-hour photoperiod, and 25/18°C day/night temperature weighed over 40 times more than those grown in the greenhouse under natural daylight supplemented by 200 ft-c (2.16 klx) of cool-white fluorescent light, a 16-hour photoperiod, and 24/18°C day/night temperature. Compared with plants grown under low light intensity, plants grown for 8 weeks under high light intensity were 6 times taller, had twice as many leaves, and produced lateral shoots containing 17 times as much dry matter. These findings indicate the feasibility of using high light intensity alone at the seedling stage in the commercial production of planting stock of this species.
The objective of this study was to determine the feasibility of CO2 enrichment and optimal radiation level for accelerating the rooting and growth of micropropagated Kalmia latifolia cuttings during the Stage IV acclimation period. Inch long microcuttings of the Kalmia cultivars `Elf' and `Carousel' shipped from a commercial micropropagation laboratory, were stuck in flats of peat, and place in a fogging chamber constructed to allow for the simultaneous experimental variation of CO2 level and either radiation level or photoperiod. Treatments consisted of a complete factorial arrangement of 2 levels of CO2 (ambient and 1200 ppm) and 3 levels of radiation (30, 98, and 158 μmoles/m2/sec). The experiment was repeated 6 times. For `Carousel' CO2 enrichment stimulated both shoot and root growth and either the high or medium light level was optimal depending on the experiment. CO2 enrichment also stimulated growth of `Elf' but results were less consistent from experiment to experiment. Similar experiments are in progress with Amelanchier and Lilac microcuttings.
Mature hedgerow walnut trees (Juglans regia L. cv. Chico) were irrigated at rates of 33, 67, and 100% of potential orchard ETc (about 350, 700, and 1050 mm/season, respectively) for three years. All trees were then returned to 100% ETc for the subsequent three year period.
Deficit irrigation reduced vegetative growth as measured by shaded area of the orchard floor and trunk growth. Yield reductions, which were minimal after one season, were significantly greater in years two and three. However, the relationships between crop yield and applied water were linear for all deficit irrigation seasons. Upon a return to full irrigation, trunk (and presumably shoot) growth of the previously stressed trees accelerated to levels greater than the control. The subsequent increase in fruiting positions resulted in a return to full production after two years. This suggests that hedgerow walnuts have the potential to recover rapidly from drought-induced production losses if no secondary effects of tree water stress, such as disease or pests, occur.
Gibberellins (GAs) are increasingly proving to be a crucial regulator of plant growth and a controlling factor of plant architecture. They regulate various physiological and biochemical processes of plant growth and development, promote germination