A fresh look at an ancient technique: a cellular perspective on seed priming

Abstract

Seed priming is a vital pre-sowing technique that enhances germination speed, synchronization, and stress tolerance in crops. While its field benefits are well-established, the precise cellular and metabolic adjustments that rules cultivar-specific responsiveness under varying environmental conditions remain poorly understood. This thesis aimed to elucidate these underlying mechanisms, using a comprehensive cellular perspective. Thus, it is presented in two parts: Chapter 1 provides a review detailing the physiological alterations induced by priming, establishing the relationship between cellular hydration status and the subsequent increase in germination uniformity and stress tolerance mechanisms. Chapter 2 encompasses an original research paper that investigates whether priming-triggered mechanisms are affected by temperature extremes, using two Sorghum bicolor (L.) Moench cultivars, BTx623 and RTx430. Germination performance was evaluated across a temperature range, with detailed analyses conducted at optimum (25 ºC) and low-temperature stress (10 ºC) conditions. Through a multi-faceted approach, including untargeted metabolomics, mitochondrial electron microscopy, and respiration performance assays using inhibitors, we uncovered two distinct metabolic strategies by the cultivars, characterized by either a great accumulation and stabilization of key protective metabolites or remarkable plasticity that rapidly shifts the metabolite accumulation in response to the condition. This metabolic reprogramming ensures that the resulting primed seed is metabolically pre-conditioned, effectively shortening the rate-limiting lag phase of germination. At the end, this work elucidates the cellular basis of priming efficacy and emphasizes the necessity of considering genotype-specific metabolic endpoints for optimizing seed enhancement applications under a changing climate.