What is the Difference Between Orthodox and Recalcitrant Seeds?

Orthodox and recalcitrant seeds differ in their ability to withstand drying and freezing during ex-situ conservation. Here are the key differences between the two:

• Orthodox Seeds:
• Can survive freezing and drying during ex-situ conservation.
• Can be dried to an internal seed moisture of less than 12% water and stored at freezing temperatures.
• Exhibit low sensitivity to desiccation, allowing them to survive for a longer time in storage.
• Examples include most food grains, legumes, guava, capsicum, sapota, dates, and cashews.
• Recalcitrant Seeds:
• Cannot survive freezing and drying during ex-situ conservation.
• Cannot be dried below relatively high moisture levels (25 to 45%) and therefore cannot be stored at subfreezing temperatures.
• More sensitive to desiccation, leading to oxidative damage or deterioration of cells.
• Examples include mango, avocado, cocoa, lychee, and jackfruit.

Orthodox seeds can be stored for a longer time in conventional seed banks, while recalcitrant seeds require alternative storage methods due to their inability to withstand the drying and freezing conditions used for orthodox seeds.

Comparative Table: Orthodox vs Recalcitrant Seeds

Here is a table comparing the differences between orthodox and recalcitrant seeds:

Orthodox seeds can survive freezing and drying during ex-situ conservation, while recalcitrant seeds cannot. Orthodox seeds can be dried to low moisture contents and are desiccation-tolerant, making them suitable for long-term storage. In contrast, recalcitrant seeds require higher moisture levels for storage and are not desiccation-tolerant, which makes their storage more challenging.