Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: Marshall J. McFarland x
  • All content x
Clear All Modify Search
Free access

Ismail A. Hussein and Marshall J. McFarland

Two-year-old, greenhouse-grown, potted `Granny Smith' apple (Malus domestica Borkh.) trees grafted on seedling, M.7 EMLA, or Mark rootstock were subjected to water stress by withholding irrigation for three successive days. Sap flow rates were measured with steady-state, heat-balance stem gauges; daily water use was measured with an electronic balance; and instantaneous transpiration was measured with a diffusion porometer. Differences in the sap flow among the three rootstocks were observed by the third day of stress treatment. The cumulative sap flow over the 3-day stress period was higher for trees on seedling and M.7 EMLA rootstocks than for those on Mark. Cumulative sap flow was reduced on the second and third days of water stress compared to sap flow in the control. The diurnal peak of sap flow rate was flattened on the second and third days of stress compared to the pattern for the control and first day of stress treatment. In general, the trees on the standard rootstock (seedling) were least affected by the water stress; trees on the full dwarf rootstock (Mark) were the most affected. Good agreement between cumulative sap flow measurements and gravimetric measurements indicates that the steady-state, heat-balance method is practical and accurate.

Free access

Susan L. Steinberg, Marshall J. McFarland, and Josiah W. Worthington

The potential for reducing water use of peach [Prunus persica (L.) Batsch] trees with antitranspirants following fruit harvest was investigated using matched peach trees planted in an outdoor twin weighing lysimeter facility. A 10% solution of the antitranspirant Wilt Pruf NCF was applied to one of the two trees on 7 July 1986. Immediately after application, water use of the treated tree was reduced by 40%. One month after treatment, the water use was reduced 30% and, by the termination of the experiment (85 days after treatment), water use was reduced 12% as compared to control. The average reduction in tree water use for the entire period was 30%. Fully expanded, sunlit leaves (nodes 10 to 20 from the terminal end) from the treated tree exhibited the greatest reduction in water loss compared with immature or inner canopy, shaded leaves. Use of the antitranspirant did not prevent the development of water stress once a critical level of soil moisture was reached. The change in tree water use induced by the antitranspirant did not significantly reduce shoot length, new leaf production, or individual leaf size on actively growing, current-season branches. Fruit and leaf bud initiation, as measured the following spring, were not affected: however. flower bud maturation could not be evaluated due to freeze damage. Chemical name used: di-1-p-menthene (Wilt Pruf NCF).

Free access

Susan L. Steinberg, Jayne M. Zajicek, and Marshall J. McFarland

Growth of potted hibiscus (Hibiscus rosa-sinensis L.) was limited either by pruning or by a soil drench of `uniconazole at 3.0 mg a.i. per pot. Both treatments changed the water use of hibiscus. Five days after treatment with uniconazole, plants showed reduced water use, an effect that became more pronounced with time. Water use of pruned plants was reduced immediately after pruning, but soon returned to the level of the control due to the rapid regeneration of leaf area. Pruned or chemically treated plants used 6% and 33% less water, respectively, than the control. Chemically treated plants had a smaller leaf area, and individual leaves had lower stomatal density, conductance, and transpiration rate than control plants. Under well-watered conditions, the sap flow rate in the main trunk of control or pruned plants was 120 to 160 g·h-1·m-2, nearly three times higher than the 40 to 70 g·h-1·m-2 measured in chemically treated plants. Liquid flow conductance through the main trunk or stem was slightly higher in chemically treated plants due to higher values of leaf water potential for a given sap flow rate. The capacitance per unit volume of individual leaves appeared to be lower in chemically treated than in control plants. There was also a trend toward lower water-use efficiency in uniconazole-treated plants. Chemical name used: (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-l-yl)-1-penten-3-ol (uniconazole).

Free access

Susan L. Steinberg, Jayne M. Zajicek, and Marshall J. McFarland

Growth of potted Ligustrum was controlled by uniconazole at 3.0 mg a.i./pot. Uniconazole inhibited growth by inducing shorter internodes with smaller diameter and by reducing secondary branching and new leaf production. As a result, the total leaf area of the treated plants was 6396 less than the control plants. The chlorophyll content of recently expanded leaves was 27% lower in treated than in control plants, even though there were no visual differences in leaf color. Leaves of treated plants also had a 28% higher stomatal density than the control. The liquid flow conductance of Ligustrum was 3.7 × 10-14 m·s-1·Pa-1 and was similar for plants in both treatments. Differences in daily water, use between the two treatments began to appear at the same time as differences in growth. Total water use of treated plants was 13% less than that of the control. When daily water use was normalized on a-leaf-area basis, water use between treatments was similar, suggesting that differences in total water use were primarily due to differences in leaf area. For plants in both treatments, peak sap flow rates in the main trunk ranged between 60 and 100 g·h-1·m-2. Leaf conductance, transpiration rates, and water potential were also similar for treated and control plants. Chemical name used: (E)-1-(4-chlorophenyll) -4,4, -dimethyl-2-(l,2,4-triazo1-l-y1)-l-penten-3-ol (uniconazole).

Free access

Jayne M. Zajicek, Susan L. Steinberg, and Marshall J. McFarland

Growth of ligustrum (Ligustrum japonicum `Texanum') was controlled by the application of the growth regulator, uniconizole, at 3 mg A.I. per 7.6 liter pot. Seventy-nine days after application, growth regulated plants had shorter internodes, smaller stem diameters and reduced secondary branching and new leaf production. Differences in daily water use between the two treatments began to appear at the same time that differences in growth became apparent. Total water use of treated plants was 13% less than the control. When daily water use was normalized on a leaf area basis, water use between treatments was similar, suggesting differences in total water use were primarily due to differences in leaf area. Under well-watered conditions, the sap flow rate in the main trunk of plants in both treatments ranged between 60 and 100 g h-1 m-2 of stem area. Leaf conductance, transpiration rate and water potential were also similar for treated and control plants.

Free access

Susan L. Steinberg, Jayne M. Zajicek, and Marshall J. McFarland

Growth of potted hibiscus (Hibiscus rosa-sinensis Ross Estey) plants was controlled by either pruning or the growth regulator, uniconazole, at 3.0 mg a.i. per pot. Five days after treatment with uniconazole, plants showed reduced water use, an effect which became more pronounced with time. Water use of pruned plants was reduced immediately after pruning, but soon returned to the level of the control due to the rapid regeneration of leaf area. Chemically treated and pruned plants, respectively, used 33% and 6% leas water than the control. The reduction in water use due to the use of uniconazole had both a morphological and physiological component. Chemically treated plants had a smaller leaf area, and individual leaves had a lower stomatal density, conductance and transpiration rate than leaves of control plants. Under well watered conditions, the sap flow rate in the main trunk of control or pruned plants was 120-160 g h-1 m-2, nearly three times higher than the 40-60 g h-1 m-2 measured in plants treated with uniconazole.