Date of Award:

5-1973

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Botany

Committee Chair(s)

Frank B. Salisbury

Committee

Frank B. Salisbury

Committee

Orson S. Cannon

Committee

William F. Campbell

Committee

David R. Walker

Committee

Devon Doney

Abstract

Five day old dark-grown seedlings of Secale cereale variety "cougar" grown at 20 C were subjected to hardening at 2 C in daily increments from 0 to 7 days, to temperature stress at -5 C for 0, 1, and 3 days, and to recovery at 20 C for 0, 1, and 3 days. Unhardened plants were killed by temperature stress but as the time of hardening increased fewer plants were killed. After 5 days of hardening all plants survived subsequent freezing stress.

Mitochondria were isolated from the plants after they received various combinations of the three temperature treatments. There were 8 hardening levels, 3 stress levels, and 3 recovery levels giving a total of 8x3x3=72 treatments. Mitochondria from unstressed plants exhibited steady ADPIO ratios, RC ratios, and rate of state 3 respiration over the whole range of hardening and recovery times. Mitochondria from stressed plants were totally inactive with 0 or one day of hardening but as the time of hardening increased so did ADP:O ratio, RC ratio, and rate of state 3 respiration. After 5 days of hardening mitochondria from hardened then stressed plants reached a maximum level of activity.

Evidently there was some change 1n the mttochondria during the hardening phase.

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17c912d533b17f58ee147473361ac2c3

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