| This paper studied on the physiological mechanism of different Lily seedlings under low temperature stress, using12market popular commercial varieties and2wild species lilies as experimental materials. By variance analysis and subordinate function analysis of the variations in the relative conductivity, proline, MDA, SOD activity, CAT activity of Lily seedlings under low temperature stress, a comprehensive evaluation of cold resistance of12commercial varieties and2wild species had been made. Base on this comprehensive evaluation of cold resistance the good cold resistance and popular commercial variety’Robinna’had been selected to detect its photosynthetic indexes so as to study the photosynthesis physiological mechanism of Lily under low temperature stress. The main results concluded as follows:1. Relative conductivity of Lily showed an upward trend under low temperature stress at the initial treated stage, but most of the varieties (species) of Lily showed the declining trend after treated3to7days, while L. davidii var unicolor Cotton, Lilium regale Wilson,’Snow Queen’,’White Fox’ had been showing a slight rise trend and the relative conductivity of ’Janna’ rose by only7.00%showing the smallest rate after15days of the low-temperature stress treated.2. After15days of the low-temperature treated, the proline content of all lilies varieties (species) both increased, in which ’Robinna’ increased by the highest rate of36.39%.3. After1days of the low-temperature treated, the MDA content of lily increased. Among these varieties (species), the largest rising ratio is ’Lyon’. It shows that its cold resistance is weaker than others. After treated3to7days, the MDA content of the most varieties (species) showed a initial rising trend to the downward trend. No permanent damage was caused on Lily within this treated period that lily still was capable to endure.4. In the15days of the low temperature stress, the correlation of SOD activity and the cold resistance of lily was extremely significant, which showed that SOD activity could be selected as one of the reliable index of lily cold resistance evaluation. After15days of the low-temperature treated, the better cold resistance varieties of lily remained significantly higher SOD activity. But the regularity of CAT activity was not obvious, which was not recommended as a separate index to evaluate the cold resistance of lily.5. Cold resistance mechanism of plants is a complex physiological and biochemical processes, the strength of its cold resistance is the results (which controlled by complex factors), rather than a single factor for the decision. So the subordinate function method was chosed to evaluate comprehensibly the cold tolerance of14varieties (species). The strength of Cold resistance in the order is:’Janna’>’Robinna’>’Siberia’>’Yellowween’>’Montdemarsan’> L. davidii var unicolor Cotton> Lilium regale Wilson>’White Fox’>’Snow Queen’>’Royal Sunset’>’Royal Song’>’Ceb Glow’>’Lyon’>’Brunello’.6. After low temperature stress, the chlorophyll b in the lily leaves damaged more serious extent than chlorophyll a, which could be inferred that it damaged firstly antenna components of PS Ⅰ and PS Ⅱ in the lily leaf chlorophyll, followed by the core complex matter of photosynthetic system.Under the sustained low temperature stress, the light saturation point of lily lowered down and compensation point increased, available spectral regions narrow and assimilation capacity weaken, carbohydrate accumulation reduced and the ability to withstand adversity reduced. Under the initial low temperature stress stage, the photosynthesis of lily was inhibited by low temperature stress that made stomatal conductance reduced which is included in stomatal factors, while under the later low temperature stress it compared to nonstomatal factors that led to the inhibition of photosynthesis of lily... |
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