Biochemical and histological changes in Dendrobium sonia-28 protocorm-like bodies (PLBs) at various low temperatures and under mineral oil layer

The study was conducted on the storage of Dendrobium sonia-28 protocorm-like bodies (PLBs) at various temperatures (5, 10, 15, 20, and 25 degree C) and under mineral oil layer. Biochemical analyses were conducted on the PLBs by determining the chlorophyll, total soluble protein and peroxidase activities. In addition, histological analyses of cell structure, rate of survival and shoot growth after the recovery process were carried out. This study was performed in two conditions; three (3) weeks and twelve (12) days of growth recovery period after 3 weeks of storage treatment. The PLBs were transferred to half strength Murashige and Skoog (MS) medium containing 1.0 mg/L benzylaminopurine (BAP) and kept at 25 plus or minus 2 degree C for twelve (12) days during recovery period. Overall, PLBs stored under 5 degree C and mineral oil layer produced the lowest values in chlorophyll analysis, rate of survival and shoot growth. However, total soluble protein content was increased during twelve (12) days of growth recovery period. Histological analysis has shown that the cell structure of these PLBs sustained a high degree of damage due to the treatment. PLBs stored under 5 degree C and mineral oil layer recorded the highest peroxidase activity attributed to higher stress conditions.