Showing papers by "William B. Miller published in 1996"

Iron Toxicity Stress Causes Bronze Speckle, a Specific Physiological Disorder of Marigold (Tagetes erecta L.)

Abstract: A specific physiological disorder, bronze speckle (J.P.A.'s nomenclature), was consistently induced in 'First Lady' and 'Voyager' marigold with Fe-DTPA concentrations greater than 0.018 m M Fe-DTPA (1 ppm) applied to a soilless medium. The disorder was characterized by specific symptomology distinguished visually by speckled patterns of chlorosis and necrosis, and downward curling and cupping of leaves. The percentage of total leaf dry weight affected with symptoms generally increased with increasing Fe-DTPA treatments. Symptomatic leaf tissue had a greater Fe concentration than corresponding asymptomatic leaf tissue. Leaf Mn concentrations in symptomatic and asymptomatic tissue were similar. In 'First Lady', older leaf tissue accumulated more total Fe and was associated with more severe symptoms than younger tissue. Media leachate Fe concentrations increased over 6 weeks and were larger at greater Fe- DTPA treatments. Adjustment of nutrient solution pH to 4.0, 5.25, or 6.5 did not alter media pH, nor did it prevent disorder symptoms. Application of Fe-DTPA containing nutrient solution to a soilless medium resulted in leachate Fe levels 3 times greater than for FeSO 4 treatments. Chemical names used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).

Low-temperature Storage of Rooted Chrysanthemum Cuttings: Relationship to Carbohydrate Status of Cultivars

Abstract: Low-temperature storage potential of rooted cuttings of garden chrysanthemum ( Dendranthema ×grandiflorum (Ramat.) Kitamura) cultivars and its relationship with carbohydrate reserves were evaluated. Storage of chrysanthemum cuttings at -1 and -3 °C resulted in freezing damage. Visual quality of rooted cuttings stored at 0 or 3 °C varied among cultivars. Quality of 'Emily' and 'Naomi' cuttings was reduced within a week by dark storage at 0 or 3 °C due to leaf necrosis, while 'Anna' and 'Debonair' cuttings could be held for 4 to 6 weeks without significant quality loss. In 'Anna' and 'Debonair', low- temperature storage reduced the number of days from planting to anthesis regardless of storage duration. However, flowers of plants grown from stored cuttings were smaller than those of nonstored cuttings. At the beginning of storage, 'Emily' and 'Naomi' had lower sucrose, glucose, and fructose (soluble sugars) content compared to 'Anna' and 'Debonair'. Regardless of temperature, leaf soluble sugar was significantly reduced by dark storage for 4 weeks. In stems, sucrose and glucose were reduced while fructose generally increased during low-temperature storage probably due to the breakdown of fructans. Depletion of soluble sugars and a fructan-containing substance during low-temperature dark storage was greater in 'Emily' and 'Naomi' than in 'Anna' and 'Debonair'. Low irradiance (about 10 μmol·m -2 ·s -1 photosynthetically active radiation (PAR) from cool-white fluorescent lamps) in storage greatly improved overall quality and delayed the development of leaf necrosis in 'Naomi'. Cuttings stored under light were darker green and had a higher chlorophyll content. Leaf and stem dry weights increased in plants stored under medium and high (25 to 35 μmol·m -2 ·s -1 PAR) irradiance while no change in dry weight was observed under dark or low light. Results suggest that the low-temperature storage potential of chrysanthemum cultivars varies considerably, and provision of light is beneficial in delaying the development of leaf necrosis and maintaining quality of cultivars with short storage life at low temperatures.

Iron Deficiency Stress Influences Physiology of Iron Acquisition in Marigold (Tagetes erecta L.)

Abstract: Excised roots of 'First Lady' marigold ( Tagetes erecta L.) grown in an aerated 0 Fe nutrient solution had Fe(III)- DTPA reductase activity 14-fold greater, and an enhanced ability to acidify the rhizosphere than plants grown in a solution containing 0.018 mM (1 ppm) Fe-DTPA. Reductase activity and rhizosphere acidification of plants grown in 0.018 and 0.09 mM Fe-DTPA were similar. Manganese concentration in leaves of plants grown in the 0 Fe treatment was 2-fold greater than in leaves of plants grown in the 0.018 m M Fe-DTPA treatment. These results indicated that 'First Lady' marigold is an Fe-efficient plant that possesses both an inducible or adaptive reductase system and the ability to acidify the rhizosphere, and that these Fe-efficiency reactions do not occur when Fe is sufficient. Chemical name used: ferric diethylenetriaminepentaacetic acid, monosodium salt (Fe-DTPA).