Study on cell structure, physiology, and biochemistry of vascular bundle blackening in petals of Chimonanthus praecox (L.) Link

We observed the microstructure and ultramicrostructure and measured the physiological and biochemical indices of vascular bundle blackening in petals of Chimonanthus praecox (L.) Link. Results showed that moderately blackened petals exhibited vacuole wall blurring, granular substance increase, and plastid coagulation and blockage. As vascular bundle function was gradually lost, the basic tissue cells became dehydrated, but the epidermal cells remained relatively full to maintain basic flower functions. As the degree of vascular bundle blackening intensified, peroxidase (POD) activity and free amino acid content increased, whereas the soluble sugar content decreased, consistent with the physiological characteristics of flower senescence. However, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and soluble protein content did not decrease significantly, indicating that the C. praecox flower possessed a strong ability to adapt to adversity, and the degree of membrane lipid peroxidation was not high. In addition, the membrane and internal structures of most cells were relatively undamaged. This study provides a theoretical basis for further study on the formation mechanism of this phenomenon and the final solution to this problem.