Robert L. Wample

Leaf water and carbohydrate status of VA mycorrhizal rose exposed to drought stress

SummaryShoot water relations and carbohydrate levels were compared for droughted nonmycorrhizal and vesicular-arbuscular (VA) mycorrhizalRosa hybrida L. cv ‘Samantha’ plants grown with high and low phosphorus fertilization. Leaf diffusive conductance (gi) of plants colonized byGlomus intraradices Schenk and Smith andGlomus deserticola Trappe, Bloss and Menge were 2 × and 1.5× greater, respectively, than in nonmycorrhizal plants. Regardless of P fertilization, leaf osmotic and bulk water potentials were 0.5 to 1.1 MPa higher in mycorrhizal than in nonmycorrhizal plants. Leaf starch, chlorophyll and water contents while fructose, glucose and total soluble carbohydrates were lower. Level of P fertilization had no effect on water relations or soluble carbohydrate content of nonmycorrhizal roses. The water status of droughted rose was impoved more byG. intraradices than byG. deserticola.

Water use of Vitis vinifera grapes in Washington

Abstract A long-term research project was initiated in 1983 on a 1.2 ha trickle-irrigated Vitis vinifera vineyard to address water management of White Riesling (WR), Chenin blanc (CB), and Cabernet Sauvignon (CS) grapes in central Washington. Six large drainage lysimeters, two per cultivar, were installed to monitor crop water use. Each lysimeter contained two vines. Vines were balance pruned and shoot-thinned to achieve an equivalent crop level of about 15 Mg/ha of grapes. Analyses showed that published crop coefficients (ET o ) for mature grapes greatly overestimate water use early and late in the season for Washington conditions although peak crop coefficients of about 0.8-0.9 were similar. Annual crop water use for all three cultivars ranged from 130 mm for one-year-old vines in 1985 to as much as 540 mm for mature vines in 1990. The average crop water use for small, young vines (1985–1986) was about 146 mm/yr, and from 1987–1990 for mature plants it was about 417 mm/yr for all three cultivars.

Effects of paclobutrazol on growth, photosynthesis and carbohydrate content of ‘dDlicious’ apples

Abstract Paclobutrazol(2R,3R+2S,3S)1-(4chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3-ol) at 25, 50 and 150 mg active ingredient was applied as a soil drench or stem application to 1-year-old ‘Topred Delicious’ apples. Both application methods reduced leaf area, leaf fresh weight and leaf dry weight. Stem applications reduced shoot length to a further extent than soil applications. Soluble carbohydrate levels were increased in the stem-treated plants. Photosynthetic rate, transpiration rate and chlorophyll content were not affected.

Root growth, water relations and mineral uptake of young ‘Delicious’ apple trees treated with soil- and stem-applied paclobutrazol

Abstract Paclobutrazol (2R,3R + 2S,3S)-1-(4 chlorophenyl)-4,4-dimethyl-2-(1,2,4-trizol-1-yl) pentan-3-ol), at 25, 50 and 150 mg active ingredient, was applied as a soil drench or stem application to 1-year-old ‘Topred Delicious’ apples. Root growth measured as relative root surface area was reduced by both soil and stem applications. There was no significant difference in dry weight of the root tissue. The root-to-leaf-area ratio was significantly increased in paclobutrazol-treated plants. Water relations measured as leaf conductance and leaf water potential were significantly influenced by paclobutrazol. Leaf conductance was higher in paclobutrazol-treated plants when the plants were turgid, as well as under some water stress. Leaf water potential was significantly higher in treated plants. There were no significant differences in the total nitrogen, phosphorus, potassium and magnesium levels found in the leaf or root tissue.

Yield and quality of furrow and trickle irrigated hop (Humulus lupulus L.) in Washington State

Abstract The results of a 2 year study of the effect of trickle and furrow irrigation methods on hop production in a desert region in northwest United States are presented. Also discussed are the implications to hop production in areas with higher rainfall. Trickle, furrow, and cutback furrow irrigation systems and their associated methods of fertilization were evaluated in a commercial hop yard. Leaf diffusive resistance, leaf water potential, alpha and beta acid content, and yield were measured. Also monitored was the efficiency of irrigation water use and the intregration of these irrigation methods with commercial crop production practices. Trickle irrigation with fertilizer injection provided several crop management advantages but required changes in cultivation practices. In the 2nd year of study, the highest yield and quality of hop was obtained from trickle irrigated plots which received the least amounts of water, fertilizer and labor inputs.

A rapid field method for measuring net assimilation rate-stomatal conductance relationship: a feasibility test using grapevine leaves

Abstract Based on the assumption that the response time of the photosynthetic apparatus to changes in light intensity is faster than the response time of stomata, a rapid field method for measuring the assimilation rate (A) stomatal conductance (gs) relationship in wine-grapes is proposed. Leaves from the outer canopy of Vitis vinifera L. cultivar ‘Cabernet sauvignon’ were placed between two pieces of foam for 90 min to reduce light intensity and induce stomatal closure, while allowing water vapor diffusion to occur. Heat load was reduced by shading the foam with a piece of light colored, heavy paper attached to the foam with a 10 mm air space between them. When the cover was removed, A and gs were measured several times until no significant changes in gs were observed. The A g s relationships of the leaves were similar in spite of differences in the response time between leaves. Very few exceptions to the A g s curves existed, and these leaves were easily identified. This procedure permits an analysis of the A g s relationship without the complications of different plant water potentials that are normally used to achieve different levels of gs.