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- Author or Editor: John W. Williams x
Abstract
All fungicides applied as dips to polyurethane propagation cubes prior to propagation of poinsettia (Euphorbia pulcherrima Willd.) cuttings inhibited rooting at the concentrations employed. Least inhibition of rooting resulted from dips containing (per liter) either 37 mg metalaxyl [N-(2,6 dimethylphenyl)-N-(methoxyacetyl) alanine methyl ester] 25 WP plus 300 mg ferbam (ferric dimethyldithiocarbamate) 76 WP, 500 mg ferbam 76WP, or 599 mg benomyl [methyl l-(butyl-carbamoyl)-2-benzimidazole-carbamate] 50 WP. Treatments containing fenaminosulf (p-dimethylaminobenzenediazo sodium sulphonate) 35 WP inhibited rooting most. The PCNB (pentachloronitrobenzene) 75 WP treatment also caused low root counts.
Abstract
Cuttings of poinsettia (Euphorbia pulcherrima Willd.) treated with a basal dip of 0.1% indolebutyric acid (IBA) alone (control) or in combination with 5% ferbam (ferric dimethyldithiocarbamate), benomyl [methyl 1-(butyl-carbamoyl)-2-benzimida-zole-carbamate], metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyl) alanine methyl ester], PCNB (pentachloronitrobenzene), and ethazol (5-ethoxy-3-tricloromethyl-l,2,4-thiadiazole) did not differ in rooting index or weight. Increasing the percentage of fungicide above 5% generally reduced rooting. However, rooting was similar to the control with combinations of ferbam at 5% to 67% or metalaxyl at 20%. Fenaminosulf (p-dimethylaminobenzenediazo sodium sulfonate) at 5% to 67% reduced rooting.
Pecan [Carya illinoinensis (Wangenh.) C. Koch `Melrose'] and pear (Pyrus calleryana Decne. `Bradford') trees in the nursery grew more in containers designed to hold water in the lower portion. The water-holding reservoir was obtained either by placing 76-liter containers in a frame holding water to a depth of 6 cm or by using containers with drainage holes 6 cm from the bottom. Continuous waterlogging at the bottom of containers resulted in root pruning and root death in the lower portion of the containers, but roots grew well above the constantly wet zone. Fresh weight of plant tops and trunk diameters were greater after two growing seasons in the containers with water reservoirs compared to those grown in similar containers with no water reservoirs. Total root dry weight was unaffected.
Because sweetpotato [Ipomoea batatas (L.) Lam.] stem cuttings regenerate very easily and quickly, a study of their early growth and development in microgravity could be useful to an understanding of morphological changes that might occur under such conditions for crops that are propagated vegetatively. An experiment was conducted aboard a U.S. Space Shuttle to investigate the impact of microgravity on root growth, distribution of amyloplasts in the root cells, and on the concentration of soluble sugars and starch in the stems of sweetpotatoes. Twelve stem cuttings of ‘Whatley/Loretan’ sweetpotato (5 cm long) with three to four nodes were grown in each of two plant growth units filled with a nutrient agarose medium impregnated with a half-strength Hoagland solution. One plant growth unit was flown on Space Shuttle Columbia for 5 days, whereas the other remained on the ground as a control. The cuttings were received within 2 h postflight and, along with ground controls, processed in ≈45 min. Adventitious roots were counted, measured, and fixed for electron microscopy and stems frozen for starch and sugar assays. Air samples were collected from the headspace of each plant growth unit for postflight determination of carbon dioxide, oxygen, and ethylene levels. All stem cuttings produced adventitious roots and growth was quite vigorous in both ground-based and flight samples and, except for a slight browning of some root tips in the flight samples, all stem cuttings appeared normal. The roots on the flight cuttings tended to grow in random directions. Also, stem cuttings grown in microgravity had more roots and greater total root length than ground-based controls. Amyloplasts in root cap cells of ground-based controls were evenly sedimented toward one end compared with a more random distribution in the flight samples. The concentration of soluble sugars, glucose, fructose, and sucrose and total starch concentration were all substantially greater in the stems of flight samples than those found in the ground-based samples. Carbon dioxide levels were 50% greater and oxygen marginally lower in the flight plants, whereas ethylene levels were similar and averaged less than 10 nL·L−1. Despite the greater accumulation of carbohydrates in the stems, and greater root growth in the flight cuttings, overall results showed minimal differences in cell development between space flight and ground-based tissues. This suggests that the space flight environment did not adversely impact sweetpotato metabolism and that vegetative cuttings should be an acceptable approach for propagating sweetpotato plants for space applications.