Date of Award:

5-1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

J. LaMar Anderson

Committee

J. LaMar Anderson

Committee

David R. Walker

Committee

Gaylen L. Ashcroft

Abstract

The length of the 'Concord' grape rest period was evaluated during 1974-75 and 1975-76. Cuttings were placed in a 25 C growth chamber every two weeks from October through April. Number of days to reach 50 percent full bud swell was plotted to determine rest completion. Seven years of weather data and full bloom dates of 'Concord' grapes from Prosser, Washington were statistically analyzed to give another estimate of rest completion. Rest was terminated after about 830 chill units.

During 1974-75 and 1975-76, T50 temperatures were determined every two weeks for both cambium and primary buds of 'Concord' grapes. The cambium ranged 2 to 10 C hardier than the primary buds. The T50 temperature pattern correlated with the minimum ambient air temperatures.

Cuttings, collected and placed in growth chambers, were analyzed for both optimum and base temperatures. Optimum bud growth and development occurred at 25 C. The base or temperature of first noticeable bud development was approximately 4.4 C.

Bud phenological stages were followed both years and a standard set of pictures of representative stages was compiled. The growing degree hours (GDH) from end of rest to first bud swell through full bloom to maturity were determined.

A regression line was plotted between the various GDH requirements for the percent soluble solids acquired during the 1975 and 1976 seasons. The GDH accumulation and soluble solids were well correlated with an r2 value of 0.95 percent.

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