Reduced metabolic rate indicates declining viability in seed collections: an experimental proof-of-concept

Abstract

There is increasing investment globally in seed storage facilities for a wide array of purposes, from food security to biodiversity conservation. Best practice when storing seeds in this manner is to periodically test collections for viability, such that declining viability can be used as a trigger for management actions. Typically, viability testing is time consuming and/or destructive, involving germination testing, cut-testing or a range of potential biochemical indicators. Given that respiration (i.e. metabolic activity) is the basic chemical reaction common to all forms of life, measuring metabolic rate should provide a less-destructive, simple and repeatable correlate of seed viability. We compared the viability of seed collections of known proportions of alive and dead seeds to their metabolic rates, calculated as CO2 production (V̇CO2) measured using flowthrough respirometery. To maximize the activity of the seeds and our likelihood of measuring metabolic rates, we imbibed the seeds from 12 species of angiosperms, and measured them using an open system respirometer. Measuring metabolic rate in seeds from diverse evolutionary and ecological backgrounds required us to adopt an allometric approach to account for the effects of seed size upon metabolic rate. After doing so, however, we found significant linear relationships between the known viability of our seed collections and their metabolic rates, but these relationships were unique for each species measured. These data provide substantial support to the prospect that measuring metabolic rates can be used to estimate viability of seeds in storage, however, we advocate the development and adoption of more sensitive respirometry equipment, specifically engineered for this purpose in order to achieve truly non-destructive measurements.