The Influence Of Non-rhythmical Changes Of Temperature On The Landscape Trees During Deacclimation And Cold Acclimation

Plant growth and development require appropriate conditions of temperature, andthe temperature that is below or above the optimum temperature will harm to plantgrowth. Non-rhythmical changes of temperature refer to the sudden changes oftemperature which do not vary with the diurnal and seasonal rhythm, which may leadto low and high temperature damages, and affect the normal growth of plants. Innorthern China, non-rhythmical changes of temperature is frequent, causing damageto the woody landscape plants. Pterocarya stenobtera, Metasequoia glyptostroboidesHu& W. C. Cheng, Cerasus tomentosa (Thunb.) Wall, and Kolkwitzia amabilisGeaebn are the four common ornamental tree species in landscape greening with highornamental values. In the experiment the artificially simulated non-rhythmicalchanges of temperature conditions were used through different low temperatures anddurations to determine frost hardiness and changes of related physiological indexes ofthe four species. Studying the effects of non-rhythmical changes of temperature onplants may give guidance for selecting suitable ornamental tree species with strongfrost hardiness, decide whether to take winter protection precautions and makeconcrete implementation when non-rhythmical changes of temperature occur inpractice. The main results are as follows:1. During dehardening (after the end of March), temperature that was not lowerthan-6℃for0-6hours could not harm to Metasequoia glyptostroboides, andprecautions do not need to be taken.2. During dehardening (after the end of March), temperature that was lower than-6℃for6hours and more would take danage on Kolkwitzia amabilis Geaebn, andeffective precautions should be taken. From October10to November9, thetemperature appeared to-15℃, and Kolkwitzia amabilis did not get hurt.3. During dehardening (after March27), Pterocarya stenobtera damaged whenthe temperature was lower than-6℃, moreover, if the low temperature lasts morethan6hours, we should take reasonable measures to reduce harm. During the coldacclimation period, on October10, temperature that was lower than0℃for more than6hours could damage on Pterocarya stenobtera. On November9, temperature thatwas lower than-8℃for more than6hours would harm to Pterocarya stenobtera, andcold-proof measures should be taken. 4. On April23, frost hardiness of Cerasus tomentosa weakened at-6℃withduratuon of6hours, and after that day, Cerasus tomentosa would be hurt5. During dehardening, the protein contents reduced with frost hardinessweakening; During frost hardening, the protein contents rised with the augmentationof frost hardiness, which was in accordance with the change of frost hardiness.6. During dehardening, SOD acitivity and POD acitivity reduced with frosthardiness weakening; During frost hardening, SOD acitivity and POD acitivity risedwith the enhancement of frost hardiness, which was contrary to the change of frosthardiness.