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Abstract
Almost one quarter of the land surface of the world and one third of the population is found within the area limited by the Tropic of Cancer and the Tropic of Capricorn, which geographically constitutes the tropics. None of the continental United States lies within this area.
Abstract
There is much ferment among horticulturists as to the posture of horticultural research and teaching. Some question the very existence of horticulture as a science and the need for graduate degrees in a commodity-oriented field.
Abstract
Alfred H. Krezdorn was born on April 10, 1920 in El Paso, Texas. Early years were spent in southern Texas where he graduated from Seguin High School in 1937. His BS degree with major in Horticulture was obtained at Texas A&M University in 1942. He then served in the U.S. Naval Reserve in World War II and was discharged with the rank of Lieutenant in 1946. He joined the faculty of Texas A&M University for ten years during which time he took leaves of absence to obtain the MS degree at the University of Florida in 1949 and the PhD in Horticulture from Texas A&M in 1956. He returned to Florida in 1957 as an Associate Horticulturist at the University of Florida's Citrus Experiment Station in Lake Alfred and in 1960 was appointed Head of the Department of Fruit Crops and moved to Gainesville. Administrative responsibilities were relinquished after fifteen years as Chairman when he resumed full-time research and teaching as Professor Horticulture.
Abstract
Self-pollination, emasculation and gibberellic acid (GA) were used to study translocation patterns of l4C-metabolites during flowering and fruiting in calamondin (Citrus madurensis Lour.). Radioautographs showed similar translocation patterns with self-pollination and GA. GA and self-pollination resulted in a considerably stronger mobilization of 14C-metabolites to young ovaries and developing fruits than when flowers were emasculated and no further stimulus provided. The movement of l4C-metabolites to fruits, especially in the 3-week period after anthesis, appeared essential for fruit set and development.
Abstract
The effect of rootstock on tree size, root distribution and leaf mineral content of ‘Orlando’ tangelos on 11 rootstocks was studied. Pronounced differences in depth of rooting, weight of feeder roots and tree height were detected. Depth of rooting was correlated to tree height, (r = .58, 1970; r = .83, 1971) i.e., the tallest trees had the deepest root systems. Feeder root wt and tree height were not related. The level of leaf N, K, Ca and Mg but not P was related to rootstock, suggesting a differential absorption of mineral nutrients by rootstock. The level of N appeared to be influenced by root distribution. Trees with deep extensive root systems or with a large number of feeder roots near the surface had high leaf N. Leaf K was significantly correlated with depth of rooting, (r = .96, 1970; r = .84, 1971). The results suggested the maximum performance of all rootstocks was not attained under the uniform cultural conditions of this experiment and therefore the need to examine each rootstock under conditions optimum for it.
Abstract
Roots of ‘Orlando’ tangelo (Citrus paradisi MacF. × C. reticulata Blanco) on rough lemon (C. jambhiri Lush.), sour orange (C aurantium L.), sweet orange (C. sinesis (L.) Osb.) and Rusk citrange (C. sinensis × Poncirus trifoliata Raf.) were field-sampled from depths extending to 2.5 m in a well-drained sandy soil and from about 3 m in an underlying sandy clay layer of undetermined thickness. Root anatomy and morphology were examined by light and scanning electron microscopy respectively. Epidermal hairs and radially elongated groups of hypodermal cells were observed on all roots. Root hairs differed in size and shape and hypo-dermal hairs seemed to occur more frequently on surface roots. Fibrous root bunches tended to be less branched and individual roots were smaller in diameter as sampling depth increased. General root anatomy was similar to previous descriptions.
Abstract
The pattern of soil water extraction by ‘Orlando’ tangelo (Citrus paradisi Macf. × C. reticulata Blanco) trees on rough lemon (C. jambhiri Lush.), sour orange (C. aurantium L.), sweet orange (C. sinensis (L.) Osbeck), and ‘Rusk’ citrange (Poncirus trifoliata Raf. × C. sinensis) rootstocks was studied using the neutron moderation method. Root distribution data from a previous study of the same trees were used to compare to water extraction data and to calculate “apparent root efficiencies.” Soil water loss was significantly correlated to feeder root dry weight. The general pattern of moisture extraction showed that the largest water losses initially occurred at the surface with increasing contributions from deeper roots as water from the surface layers was depleted. Roots at each depth and from each rootstock were not equally efficient. The adaptability of trees on the 4 rootstocks to the soil of the experiment site appeared to be related to their respective root distributions and efficiencies.
Abstract
After refinement, a fluorometric technique was found adequate for quantitatively determining certain gibberellins in the flowers and young fruits of navel sweet oranges. Using this method, significant changes in gibberellins were shown to occur, both in tissue concentrations and total amounts per fruit, in samples collected during the bloom and early period of fruit growth.
Two relationships, a correlation between gibberellin concentration and rate of fruit growth, and an effect of total gibberellins per fruit on cumulative fruit growth, were found. These data indicated a cause and effect relationship between endogenous gibberellins and the early stages of fruit growth of the navel orange.