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- Author or Editor: T. L. Davenport x
Fruit set in some species of citrus is greater on mixed shoots (leafy inflorescences) than on generative shoots (leafless inflorescences). Combination treatments involving water stress, cool winter night temperatures, and branch pruning were used to manipulate the number of shoots and ratios of the three shoot types in containerized `Tahiti' lime (Citrus latifolia Tan.) plants. Plants were water stressed in a greenhouse for five weeks, pruned after rewatering, transferred to the open environment, and observed three weeks later. Appropriate control plants were carried along with treated ones. Combination treatments of all three variables increased the number and ratio of mixed shoots four fold over the non-stressed, non-pruned controls. More shoots formed on non-pruned, water stressed plants than on controls. Both formed predominantly generative shoots. Shoots of pruned, non-stressed plants were predominantly vegetative. Non-pruned non-stressed plants were typical of those growing in the field exposed to cool winter nights.
Abstract
Observations of pulp and rind tissue of stylar-end breakdown in ‘Tahiti’ lime (Citrus latifolia Tan.) fruit indicate that the disorder is a result of juice invasion of rind tissue at the stylar end causing a tan, watery patch.
Flowering and fruit set characteristics were examined in the popular commercial cultivar Magaoa in an effort to elucidate the reproductive phenology of mamey sapote, Calocarpum sapota (Jacq.) Merr. [syn. Pouteria sapota (Jacq.) H.E. Moore and Stearn]. Flowers opened during the night with anthesis beginning around sunset. The length of floral opening varied according to season, ranging from 6 days in winter to a single day in summer. Bursts of new flowers generally appeared in cycles of about 7 days in declining numbers of flowers per burst until all the floral buds of a particular floral bud flush had flowered. Floral buds flowered randomly along a branch with only a few flowers open at any one time. Flower position around the branch was a factor in fruit set. Flowers and small fruitlets encircled horizontal branches in great numbers, but immature fruit most often developed from flowers located on the upper branch quadrant. The lower quadrant contained the fewest immature fruit. As fruit matured, however, more upper quadrant fruit abscised until by harvest, most mature fruit were found on the lower quadrant. The observations provide new insights into the reproductive phenology of mamey sapote.
Abstract
The influence of elevated temperature, fruit size, and juice content on the incidence of stylar-end breakdown, a postharvest disorder common to ‘Tahiti’ lime fruit (Citrus latifolia Tan.), was investigated. Freshly picked limes were placed in a water bath maintained at temperatures ranging from 25°C to 50° for 3 hours. The incidence of stylar-end breakdown in these fruit increased exponentially from 0% in those fruit incubated at 25° to 85% in fruit heated at 50°. A standard treatment of heating fruit for 3 hours at 42° was employed to determine the relative susceptibility of fruit varying in size and juice content. Limes less than 3.5 cm in diameter did not break down whereas the incidence of the disorder in fruit 3.5 cm to 7.0 cm in diameter, respectively, ranged from 2% to 63%. Fruit with greater than 50% juice content were more susceptible to the disorder than those with less than 50%, but no strict correlation was found. It is suggested that the incidence of stylar-end breakdown associated with heat is mediated by liquid expansion in juice vesicles giving rise to internal pressure sufficient to rupture these vesicles. Controlling postharvest temperature of limes and maintaining strict picking schedules so that fruit are not allowed to attain maximum size significantly reduces the incidence of the disorder.
Abstract
Treatments that inhibit production of citrus flowers, such as the presence of fruit, gibberellic acid (GA3) spray, and branch pruning, were examined on container-grown ‘Tahiti’ lime (Citrus latifolia Tan.) trees induced to flower by severe water stress lasting from 2 to 5 weeks. The presence of (or effects of recently removed) fruit located at the apex of branches inhibited production of new shoots as well as expression of the vegetative and floral nature of those shoots in basipetal lateral buds. Fruit ranging in size from 0.76 to 5.0 cm in equatorial diameter inhibited the shooting response. Shoot production and floral expression were normal on other branches. Fruit size or the amount of time fruit were present on branches were associated with the reduction in shoot and flower production. Aqueous GA3 sprays at 10−3 m concentration, applied at the onset or end of the floral inductive water stress treatment, inhibited expression of both vegetative and floral shoots. This inhibitory response dissipated as time elapsed after treatment. Pruning three branches from each tree replicate did not modify the flowering response in nonpruned water-stressed branches. The shooting response of branch units on these small trees responded independently to the presence or absence of fruit, GA3 treatment, and branch pruning.
Thidiazuron (TDZ; N-phenyl-N-1,2,3-thiadiazol-5-ylurea) stimulates axillary bud break in some horticultural crops. We are exploring its ability to initiate bud growth in mango trees in order to manipulate vegetative and reproductive shoot initiation. Axillary buds on defoliated, decapitated shoots were treated in late October, 1989 (about two months before normal floral initiation), with 0, 125, or 1000 ppm TDZ. Although timing or percent of bud-break was unaffected by TDZ, the compound influenced growth expression. TDZ (125 ppm) produced morphologically typical panicles (mixed or purely floral), while at 1000 ppm purely floral panicles were produced which were abnormally compact (similar to panicles affected by mango malformation). Non-treated buds produced only vegetative shoots. Sprays of TDZ (25 to 200 ppm) on developing panicles produced morphological anomalies in panicles such as thickening of the central axis and secondary branches, increase in flower size, and sprouting of the most basal buds on the central axis. Effect during the vegetative flushing period will be discussed.
Thidiazuron (TDZ; N-phenyl-N-1,2,3-thiadiazol-5-ylurea) stimulates axillary bud break in some horticultural crops. We are exploring its ability to initiate bud growth in mango trees in order to manipulate vegetative and reproductive shoot initiation. Axillary buds on defoliated, decapitated shoots were treated in late October, 1989 (about two months before normal floral initiation), with 0, 125, or 1000 ppm TDZ. Although timing or percent of bud-break was unaffected by TDZ, the compound influenced growth expression. TDZ (125 ppm) produced morphologically typical panicles (mixed or purely floral), while at 1000 ppm purely floral panicles were produced which were abnormally compact (similar to panicles affected by mango malformation). Non-treated buds produced only vegetative shoots. Sprays of TDZ (25 to 200 ppm) on developing panicles produced morphological anomalies in panicles such as thickening of the central axis and secondary branches, increase in flower size, and sprouting of the most basal buds on the central axis. Effect during the vegetative flushing period will be discussed.
A procedure was developed to regenerate plants via tissue culture from embryonic axes of mature avocado seeds. Explants were cultured in Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and naphthalene-acetic acid (NAA) or thidiazuron (TDZ) and NAA. Culture were kept in the dark for 7-10 days to reduce browning resulting from phenolic oxidation. Multiple shoots (5-8) were formed after transfer to light. Further multiplication were achieved using different combination of BA and NAA or TDZ and NAA. Shoots were cultured in MS supplemented with 2mg/l indolebutyric acid (IBA) for 2 weeks then transferred to MS supplemented with lg/l activated charcoal for root induction. Complete plants were obtained in vitro.
Guava (Psidium guajava L.) is an exceptional source of vitamin. C. It is also considered to be the most important cultivated species of the Myrtel family. Shoot tip and stem node were taken from seedling germinated in Murashige and Skoog medium (MS) and cultured in the same medium supplemented with 1-3mg/l benzylaminopurine (BA) and 0.1mg/l naphthaleneacetic acid (NAA) or 0.2-2mg/l thidiazuron (TDZ) and 0.1mg/l NAA. Multiple shoots (4-6) were obtained in 4-5 weeks from culture in 1-2mg/l BA and 0.1mg/l NAA, while TDZ caused abnormal shoot growth. Shoots were rooted successfully with 100% frequency in MS medium containing 2mg/l indolebutyric acid and further elongation of shoots was achieved in MS medium, supplemented with lg/l activated charcoal. Regenerated plantlets were successfully established in soil.