Growth and Protein Content of Apple in Response to Root and Shoot Temperature following Chilling

Abstract

<jats:p>Bare-root <jats:italic>Malus × domestica</jats:italic> Borkh. seedlings were chilled for 0, 600, 1200, or 1800 hours at 5C (CH). Seedlings were then placed with roots and/or shoots in all combinations of 5 and 20C forcing conditions (FC) for up to 21 days. Virtually no growth occurred at 5C FC. When the whole plant was forced at 20C, all measures of root and shoot growth increased in magnitude, occurred earlier and at a faster rate with increasing CH. Thus, roots and shoots responded similarly to chilling. When shoots or roots were subjected to 20C FC, while the other portion of the plant was at 5C, the responses were reduced in magnitude and delayed. However, the <jats:italic>overall</jats:italic> growth enhancement by chilling was not negated. Root and shoot growth enhancement by chilling appeared to be increased if the other portion of the plant was actively growing also, but not dependent on it. Growth of adventitious shoots on roots (root suckers) was greatly enhanced with increasing CH on plants subjected to 5C shoot and 20C root FC. While total root and shoot bark protein levels on a per-seedling basis were similar, protein concentrations were lower in root bark than in shoot bark. During chilling, total protein per seedling generally increased until just before the time that chilling requirements for vegetative budbreak were satisfied. Protein degradation then began, resulting in lower protein levels through 2300 CH. Rapid protein breakdown (1200 to 1800 CH, roots; 1000 to 1800 CH, shoots) occurred at about the same time that root (1000 to 1800 CH) and shoot (800 to 1800 CH) growth responses to chilling were increasing. Warm FC resulted in increased protein breakdown with increased CH and forcing time.</jats:p>

Efeito da aplicação de baixa temperatura em plantas de macieira sobre o crescimento durante a aclimatização

“…Se para alguns autores (Young & Werner, 1985;Arnould & Young, 1990) o tratamento das plantas com baixas temperaturas afeta positivamente o crescimento do sistema radicular, no presente trabalho observou-se uma diminuição no peso seco das raízes com o aumento do tempo de permanência das plantas sob baixa temperatura. Entretanto, os tratamentos não afetaram significativamente (α≤0,05) o peso da matéria seca da parte aérea das plantas ao final dos 90 dias de avaliação (Figura 5).…”

“…Contudo, o crescimento é reativado logo que as condições tornam-se novamente favoráveis. Arnould & Young (1990) afirmam que o tratamento de plantas com temperatura de 5ºC, seguido da sua transferência para condições de temperatura mais elevada (20ºC), promove maior crescimento do sistema radicular. Para estes autores, um dos efeitos do frio é a mobilização de reservas das plantas, que pode estar relacionada ao crescimento das plantas no final do período dormente.…”

Tree Root Ecology in the Urban Environment and Implications for a Sustainable Rhizosphere

“…In contrast to their shoots, which have a dormant period that can only be overcome by chilling, the roots of many temperate zone trees do not exhibit an easily identified period of innate dormancy (Richardson 1958;Taylor and Dumbroff 1975), and can respond quickly to warming soil. However, Arnold and Young (1990) found evidence with several Malus (apple) species that an innate root dormancy satisfied by low temperature exposure may exist in some tree species. Lack of moisture suppresses root growth in two ways: first by restricting water uptake that drives cell expansion, and second by increasing soil strength (see Compacted Soil as a Permeable Impediment).…”

A Review of the Effects of Transplant Timing on Landscape Establishment of Field-grown Deciduous Trees in Temperate Climates

“…In contrast to the shoots of temperate zone hardwoods, which have a dormant period that can be overcome by chilling, the roots may not exhibit an easily identifi ed period of innate dormancy (Richardson, 1958;Taylor and Dumbroff, 1975). However, Arnold and Young (1990) found evidence with several apple (Malus) species to support that some inherent dormancy may exist in the root system that is satisfi ed by low temperature exposure. Although root growth is linked to shoot growth by endogenous signals (Farmer, 1975;Larson, 1970;Richardson, 1958), root growth is strongly infl uenced by environmental factors such as soil temperature and moisture (Lyr and Hoffmann, 1967).…”