You are looking at 1 - 10 of 34 items for
- Author or Editor: Michael A. Dirr x
Salt tolerance of honeylocust (Gleditsia triacanthos inermis Willd.) was determined using 2 month-old potted seedlings salinized with 200 ml of NaCl, KCl and Na2SO4 at concentrations of 0.05N, 0.15N and 0.25N applied daily to soil. Leaflets of plants receiving Cl developed a tip and marginal necrosis while leaflets of plants receiving Na2SO4 were uninjured. Shoot dry weight of plants receiving NaCl and KCl (0.15N and 0.25N) were significantly lower than plants from control and all concentrations of Na2SO4 treatment Total soluble salts were not responsible for injury. Na had no adverse effect on growth although shoot Na levels were greater than 2% of dry weight in NaCl (0.15N and 0.25N) plants. Shoot Cl was a reliable index of the degree of salt injury, for the greater the tissue Cl, the more rapid the onset and the more severe the injury. Root Na and Cl levels were inconsistent and did not reflect the degree of injury observed. Honeylocust, although reportedly highly salt tolerant, was severely injured by exposure to Cl salts and this injury, correlated with shoot tissue analyses, suggested a specific ion effect.
Quality, the degree of excellence which a thing possesses, varies with the evaluator for excellence to one may be mediocrity to another. After considerable thought and examination of the literature, I have concluded that the quality attributes of woody ornamental plants as affected by mineral nutrition practices are not well defined. First, how exactly does one proceed to evaluate quality in a woody ornamental plant? The effects of mineral nutrition on the quality of vegetables and fruits would appear to be more obvious. Yield, color, firmness, taste, keeping quality, and chemical components may be useful traits for evaluating quality under a given set of nutritional, cultural, and environmental conditions In general quality on woody ornamentals appears to be related to visually pleasing, salable plants. There are various reports of fertilizer sources and rates on growth or appearance. I will review a limited number of these and then discuss the results of a questionnaire which was sent to nurserymen around the country concerning fertilization and woody ornamental plant production.
Cranberry plants, Vaccinium macrocarpon Ait. cv. Early Black, were grown with NO3-N, NH4-N or NO3-N + NH4-N at a concentration of 50 ppm N. Fresh weight of plants cultured on each Ν treatment was similar. Nitrate Ν was present in roots but not leaves. Ammonium Ν was present in both organs. Nitrate reductase activity was demonstrated in roots but not detected in leaves. Activity was significantly greater in roots of plants grown with NO3-N vs. NO3-N + NH4-N or NH4-N grown roots. Mycorr-hizae were not present in or on the roots and bacteria were eliminated as factors affected NO3 reduction. Results suggested cranberry was able to assimilate the NO3 form of N.
Na2SO4, K2SO4, NaCl, KCl or CaCl2 at concentrations of 0.25N were applied daily as a soil drench or foliar spray to established plants of English ivy (Hedera helix L.). Marginal leaf necrosis developed after 28 days on plants drenched with Cl salts although necrosis was evident after 7 days and the injury was more severe on plants sprayed with Cl salts. Shoot dry weights of plants treated with Cl salts were significantly less than those of control or spray SO4 treatments. Leaf necrosis was not evident on plants drenched with SO4 salts, but shoot dry weights were significantly less than those of plants sprayed with SO4 salts or water. Shoot Na was greater from spray-applied Na salts compared to soil-treatments while shoot Cl was greater in soil-treated plants compared to spray Cl treatments. Shoot Cl generally corresponded with the severity of plant injury whereas shoot Na did not.
Doublefile viburnums (Viburnum plicatum Miq. tomentosum Thunb.) were cultured at 2 pH ranges, 3 to 4 and 7 to 8, with 3 N treatments (NO3-N, NH4-N, or NO3-N plus NH4-N) supplied daily at a concentration of 1.5 meq N per pot. Fresh weights of shoots and roots from plants grown with NH4-N at pH 3 to 4 were significantly lower than from plants grown with other N treatments. Plants developed leaf necrosis and ultimately died when grown with NH4-N at pH 3 to 4. Limited leaf necrosis developed on other NH4-N treated plants. Leaf necrosis did not develop on leaves of plants grown with NO3-N at pH 3 to 4 or 7 to 8. Roots of all plants, except those grown with NH4-N at pH 3 to 4 appeared vigorous and healthy. Nitrate N was greatest in shoots of NO3-N treated plants. Shoot NH4-N levels were greatest in NH4-N treated plants and correlated with the severity of leaf necrosis. Total N concentration in shoots and roots were greatest in plants grown with NO3-N at pH 3 to 4 and NO3-N plus NH4-N at pH 3 to 4. In the growing medium, NO3-N predominated at the high pH range; NH4-N at the lower pH range. The N form and pH of the growing medium exerted marked effects on growth, and on N availability and utilization by viburnum.
The Botanical Garden was conceived in 1968 when Dr. Fred C. Davison, President, charged a committee composed of faculty from the plant sciences “to study and present a final proposal for the establishment of a ‘Living Plant Library’ at the University of Georgia.” The epithet, Living Plant Library, was used in preference to botanical garden or arboretum which evoked memories of the original botanical garden at the University that existed from 1832 to about 1855; and/or the Arboretum started on South Campus about 1908 by Dr. T.H. McHatton, Head of Horticulture. Both gardens were extinguished by the path of progress – campus construction.
Floral induction of 10 Hydrangea macrophylla (Thunb.) Ser. cultivars (`All Summer Beauty', `Dooley', `Endless Summer', `Générale Vicomtesse de Vibraye', `Lilacina', `Mariesii Variegata', `Mme. Emile Mouillère', `Nikko Blue', `Penny Mac', and `Veitchii') was evaluated to determine the remontant flowering potential. Cultivars exhibiting superior flowering potential could facilitate year-round production of florist s hydrangea and expand the geographic adaptation of hydrangeas in the landscape. Plants were tested under either 8-hour inductive short-day (SD) or 24-hour noninductive extended-day (ED) photoperiods at 24 ± 2 °C. Floral induction of H. macrophylla occurred under both SD and ED but was more rapid under SD than under ED. Shoot length and total number of nodes were significantly different for cultivars, photoperiods, and harvest dates. Significant differences in the floral initiation and development were observed among cultivars. `Penny Mac', `Endless Summer', `Lilacina', `Mme. Emile Mouillère', and `Nikko Blue' displayed significantly greater floral meristem development under SD than all other cultivars. Over the nine-week period, only `Dooley', `Endless Summer', and `Penny Mac' floral development was affected significantly greater by SD photoperiods than ED photoperiods. All others cultivars showed similar floral development under SD and ED. Stage of meristem development was highly correlated with number of nodes, but not with shoot length.
Stem cuttings from a prostrate clone of Cephalotaxus harringtonia (Forbes) K. Koch (Japanese plum yew) were taken monthly from Sept. 1994 through Aug. 1995, treated with K-IBA at 0 or 10,000 mg·liter–1, placed in a greenhouse under intermittent mist, and evaluated after 16 weeks. Cuttings taken from December to February and treated with K-IBA averaged 85% rooting, 10 roots per cutting, and a total root length of 35 cm. The next highest rooting percentages were for cuttings taken from March to May; poorest rooting occurred for cuttings taken from June to August and September to November, regardless of K-IBA application. Chemical name used: K-indole-3-butyric acid (K-IBA).
Cold hardiness levels of six cultivars of Chinese elm (Ulmus parvifolia Jacq.), `Select 380', `Orange Ribbon 740', `Emerald Isle', `Emerald Vase', `Drake', and `King's Choice', were determined over eight sample dates from 31 Aug. 1988 to 16 May 1989 and for `Emerald Vase' and `Drake', over three dates from 14 Feb. 1988 to 25 Apr. 1988. All cultivars tested achieved a maximum cold hardiness in December and January of – 21 to – 24C, except `King's Choice', which survived exposure to at least – 30C. `Emerald Isle' and `Emerald Vase' acclimated earlier (both – 9C on 31 Aug.) and reacclimated later (– 6 and – 9C, respectively, on 16 May) than other cultivars tested. `Emerald Vase' and `Drake' exhibited similar cold hardiness levels over the two years tested.
Timing and rate of acclimation and maximum low-temperature survival of eight woody taxa were determined over six sample dates from 25 Aug. 1987 to 25 Apr. 1988. Four cultivars of Acer rubrum L. (red maple) acclimated at different rates and attained different levels of midwinter cold hardiness. ‘Red Sunset’ (RS) and ‘October Glory’ (OG), northern selections, acclimated at faster rates and attained greater degrees of cold hardiness than ‘Journalism Psychology’ (JP) and ‘Upright Crown’ (UC) selected from southern seed sources. Maximum cold hardiness levels were −8C (JP), −23C (UC), −29C (RS), and −29C (OG). Amelanchier arborea (Michx. f.) Fern, (downy serviceberry) and Quercus coccinea Muenchh. (scarlet oak) developed midwinter hardiness of less than −29C and −20C, respectively. Illicium floridanum Ellis (Florida anise) and Illicium parviflorum Michx. (small anise) developed −26C and −20C midwinter hardiness, respectively. According to our data, woody taxa should be evaluated for timing and rates of acclimation and low-temperature tolerances, since performance will vary from one geographic area to another, depending on photoperiod, the timing of fall freezes, and midwinter temperatures.