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Abstract
Foliar-bract calcium (Ca) sprays and fertilization practices that altered Ca availability and supply were evaluated for their effect on marginal bract necrosis incidences of ‘Gutbier V-14 Glory’ poinsettia (Euphorbia pulcherrima Willd.). About 90% fewer marginal necrotic lesions were observed on plants receiving an 81% NO3-N and 903-ppm Ca soluble fertilizer with 10% of the total nutrients foliar-applied than on plants grown with medium-applied Osmocote 19N-2.6P-10K (47% NO3-N) or with medium-applied liquid fertilizer containing 30% or 65% NO3-N and 0 ppm Ca. Addition of 354 ppm Ca in a 53% NO3-N, or 964 ppm Ca in a 75% NO3-N medium-applied fertilizer did not significantly reduce the number of lesions compared to the same fertilizer with 0 ppm Ca or the equivalent rate of a 53% NO3-N Osmocote 14N-6.1P-11.6K. Weekly foliar-bract sprays of 432 ppm Ca from Ca(NO3)2·4H2O reduced numbers of lesions by 94% (<1.5 lesions per plant), regardless of fertilization practice. Thus, soil applications of Ca were not effective in preventing marginal bract necrosis, whereas foliar applications of Ca were highly efficacious.
Foliar chlorosis or bleaching, interveinal chlorosis, leaf edge and tip necrosis, a poor root system, and stunted growth of Eustoma grandiflorum (Raf) Shinn seedlings were associated with a medium pH of 5.0 or 5.5 but not when the values ranged from 6.4 to 7.5. The range in medium pH resulting in the best growth of seedings and flowering plants was 6.3 to 6.7. Responses to medium pH were similar, regardless of fertilizer solution pH or cultivar. Eustoma seedling and shoot fresh weights for pH 5.0 and 5.5 were only 23% to 66% of corresponding values for plants grown at pH 6.4. Leaf tissue Zn was extremely high (1050 mg·kg-l dry leaf tissue) at a medium pH of 5.0, but other macro- and micronutrients in leaves were not at abnormal levels.
Abstract
The sensitivity of 26 cultivars of tomato (Lycopersicon esculentum Mill.) were compared at 2 concentrations of SO2 in specially designed exposure greenhouses. Cultivars studied included fresh market, processing, and specialty types. Insensitive and sensitive cultivars were identified by assessment of acute SO2-induced foliar necrosis. Cultivars found to be insensitive to SO2 included: ‘Ace’, ‘Bonanza’, ‘Heinz 1350’, ‘Tarquinia Tondino’, and ‘VF 145-B 7879’. Cultivars found to be sensitive to SO2 included: ‘Bellarina’, ‘Chico IIP, ‘Flora-Dade’, ‘Red Cherry Large’, ‘SubArctic Delight’, and ‘Vetomold’.
Abstract
Comparative fumigation procedures were used to evaluate the relative susceptibility of some ornamental plant species to the toxic effects of airborne fluoride in compartmentalized greenhouse chambers. Susceptibility classification was based on the speed of development of toxicity symptoms together with the specific concentrations of hydrofluoric acid vapor causing fluorosis. Symptoms of fluoride toxic effects were recorded for use in diagnosis and evaluation of damage.
Abstract
Atmospheric fluoride occasionally adversely affects foliage plants, especially intolerant species. The present report describes susceptibility to airborne fluoride damage of 34 foliage plants determined by comparative fumigation in compartmentalized greenhouses using 4 steady-state levels of hydrofluoric acid gas. Toxicity symptoms were recorded for diagnostic and damage evaluation purposes relative to air pollution effects.
Abstract
Thirty-nine cultivars of marigold (Tagetes spp.) were exposed to sulfur dioxide to determine their relative sensitivity. Flowering plants were fumigated at 1 ppm SO2 for 4 hours or at 2 ppm SO2 for 2 hours. The average foliar injury for all leaves on individual plants ranged from 42.3% for ‘Crackerjack Mix’ at 2 ppm SO2 to 0.0% for ‘Cupid Yellow’ at 1 ppm SO2. Foliar necrosis appeared as a gray to white marginal and/or interveinal scorch 1 day after exposure. There was a tendency for interveinal necrosis to be near the midvein. The extra-floral nectaries which line the leaf margins of marigold were scorched in 15 of the 39 cultivars. This injury may be of diagnostic value. Sepals were very sensitive to SO2. Sepal injury appeared as a pinpoint scorch and as tip burn, and was apparent in some cultivars when no foliar injury occurred.
Abstract
A hypothesis was tested that the cause of a damaging marginal bract necrosis common to ‘Gutbier V-14 Glory’ poinsettia is a deficiency of Ca that is expressed when the rapidly growing bract outdistances the current supply of Ca. Plants were grown in the greenhouse in a sedge peat-EauGallie sand mix with fertility adjustments designed to moderately enhance Ca deficiency. Twice-weekly foliar applications of Ca (432 ppm) were begun at the stage of first bract coloration to attempt to prevent necrosis. In addition to bract necrosis, puckering of bracts occurred on controls but not in Ca-treated plants. In another experiment, induced Ca deficiency symptomology included bract necrosis. Calcium chloride spray essentially prevented the necrosis. Necrotic bract marginal tissue had 0.07% Ca, whereas sprayed tissue contained more than three times this Ca concentration.
Abstract
Plants of ‘Croft’, ‘Ace’ and ‘Nellie White’ grown in F- or Li-amended sand cultures had injured leaves. F-injury on ‘Croft’ developed as a semi-circular necrotic area at the margin of the leaf near its apex. The necrosis enlarged until the entire leaf tip and margin became necrotic. F injury on ‘Ace’ and ‘Nellie White’ varied from the semi-circular necrosis pattern to chlorotic or necrotic leaf margins. Injury affected only lower leaves of ‘Ace’ and ‘Nellie White’ but affected all leaves of ‘Croft’. Li injured leaves of all cultivars but the number and degree of injury were less than those produced by F. Li injury developed as chlorotic leaf margins which eventually became necrotic. In all cultivars Li injury was confined to lower leaves. ‘Croft’ was more sensitive to F and Li than ‘Ace’ or ‘Nellie White’.
‘Ace’ and ‘Nellie White’ were also grown in soil amended with dicalcium phosphate or superphosphate at both low and high lime rates and fertilized with NH4-N or NO3-N nitrogen. Plants grown with dicalcium phosphate with NH4-N or at any lime rate had no leaf injury. Plants grown with superphosphate had injured leaves, particularly at low lime rates with NH4-N. Soil and plant analysis showed a high positive correlation between superphosphate, which contains F, and leaf scorch. Soil-borne F was influenced by source of N fertilizer and lime rate. The pattern of leaf scorch from superphosphate in ‘Nellie White’ and ‘Ace’ was the same as that from NaF.
Abstract
Symptoms of fusarium wilt of tomato were less severe in plants supplied with nitrate-N and greater in those supplied with ammonium-N. Liming with calcium hydroxide decreased disease severity but this effect was negated by high ammonium-low nitrate fertilization. The combination of high nitrate, low ammonium, and lime reduced disease development additively. Fusarium oxysporum f. sp. lycopersici race 2 was more virulent when grown in liquid culture with ammonium than with nitrate as the sole N source.
Media and nutrient variables were investigated to develop methods of reducing the incidence and severity of fusarium crown rot incited by Fusarium oxysporum Schlecht. f. sp. radicis-lycopersici Jarvis & Shoemaker (FORL), a disease problem of current importance with tomato Lycopersicon esculentum Mill. Root-dip inoculated seedlings were transplanted into trays of a 1 Canadian peat: 1 vermiculite medium that had been prepared with factorial combinations of CaCO, (0.75 or 3.0 kg·m), Ca(NO) or (NH) SO (each at 225 mg N/liter), and NaCl at 0 or 2000 mg Na/liter as the experimental treatments. Crown rot was more severe with the lower CaCO rate, with (NH) SO, and supplemental NaCI. Data on fresh weight of seedlings expressed as percentage values relative to the noninoculated controls supported observations on disease severity.