Acta Univ Latv (2006) 710: 29–40

Effect of cultivation conditions on morphological and biochemical characteristics of lily explants in vitro

Abstract

Regeneration of bulblets from excised bulbscales has become the preferred method for vegetative propagation of lilies. For optimal ex vitro growth and survival during in vitro propagation of lilies bulblets need to have both a period of high temperature as well as cold storage. The objective of the present experiments was to determine the optimal sugar concentration in the medium and duration of pre-cold storage period for lily explants of Asiatic lily clone ‘NS-94’ and Trompet lily cv. ‘Mezhare’ and to relate morphological characteristics with peroxidase and polyphenol oxidase activities. Morphological parameters of lily microplants were affected by cultivation conditions, e.a., low temperature storage, length of pretreatment period before cold treatment, as well as by light regime and sucrose concentration in the medium. Growth of bulblets was strongly affected by cold treatment, leading to a significant decrease of relative mass. Root formation was inhibited by cold treatment. This effect was more pronounced in cv. ‘Mezhare’ than clone ‘NS-94’. Formation of both leaves as well as bulblets was suppressed by cold storage of lily microplants. Cold treatment resulted in an increase of oxidative enzyme activity in bulblet tissues. Prolongation of duration of pre-cold period strongly increased peroxidase and polyphenol oxidase activity in bulblets of clone ‘NS94’, the effect was more pronounced in minimum light conditions. In contrast, for cv. ‘Mezhare’, higher enzyme activities were in bulblets of lily explants showing shortest duration of pre-cold period, especially in the light. A decrease in peroxidase activity appeared to be a good indicator for coldinduced slow growth of lily explants. In part this may be associated with increased antioxidative capacity in conditions of slow growth.