Effects of seedling age and dehydration on the hypocotyl cracks of green braided seedling in Pachira macrocarpa (Cham. & Schi.) Schi

The objective of this study was to examine the effects of seedling age and dehydration on the hypocotyl cracks of green braided seedling in Pachira macrocarpa. When we braided the 12 cm tall dug up seedlings 8 or 10 days after sowing, the hypocotyl crack indices of these seedlings were smaller than 1.5 (little cracking). Crack indices increased to greater than 3.5 (severe cracking) when we braided the dug-up seedlings aged 12, 14, or 16 days. In addition, dug-up seedlings were placed in a indoor environment to dehydrate and soften the hypocotyl. The mechanical stress in hypocotyls rapidly decreased to 29.7 kpa after undergoing dehydration for 36 hours. The crack index of green braided seedling, which decreased with increased duration of dehydration, was lower than 1.5 after being dehydrated for 36 or 48 hours. However, for those that were dehydrated for 72 hours, the crack index increased to 3.2. These results imply that the cracking on the hypocotyls can be minimized by braiding the very young seedling that are 10 days old and have been dehydrated for 36 or 48 hours. Consequently, the resulting hypocotyls of the braided seedlings develop the emerald color and intact epidermis that is preferred by the consumers.