Abstract:

Outer petals of four-year-old Magnolia liliflora and M.×soulangeana were used to study the floral color parameters, pigment content, PAL and CHI activity under cold stress. The treatment temperature gradients were set as-1,-2,-3,-4,-5 and-6℃, taking natural plant petals served as controls. The results were as follows: as the temperature decreases, the lightness L^*-value and chromatic component a^*-value decreased, chromatic component b^*-value increased. The C^*-value of M. liliflora gradually decrease while M. soulangeana first increase then decrease. The anthocyanin and flavonoid content of M. liliflora decreased, while the PAL and CHI activity increased under the low temperature stress. The anthocyanin and flavonoid content of M. ×soulangeana changed slowly at the early stage of low temperature stress, and significantly decreased under-5℃ and lower temperature. The PAL and CHI activity slowly decreased with decreasing temperature. Correlation analysis showed that the anthocyanin and flavonoid content of M.×soulangeana had a significantly positive correlation with PAL and CHI, while those of M. liliflora was negative correlations with PAL and CHI. In summary, low temperature stress was a hinder to the synthesis of anthocyanin and flavonoid, disordered the activity of relevant enzymes and seriously affected the normal color expression of the 2 Magnolia species.

Key words: Magnolia liliflora, Magnolia×, soulangeana, low temperature, floral-color expression, enzymes