How Variables Like Parent, Seed Size and Desiccation Time Affect Seed Deterioration of Quercus macrocarpa L.

Abstract

Desiccation sensitivity is the main characteristic of recalcitrant seeds that poses limitations to practices such as storage and direct seeding. This study investigated the effect of parent tree, seed size, and desiccation time on seed variables, seedling growth, and starch thermal properties for Quercus macrocarpa. We expected to find an effect of parent tree, but not for the seed size due to narrow size ranges available for the study. We hypothesized that desiccation time would negatively affect seed variables and seedling growth, while starch thermal properties would also be altered. Two parent trees with distinctive pericarp characteristics (Type-1 with tougher/darker pericarp than Type-2), and two seed sizes (19.5 and 20.5 mm in diameter) for each parent were selected. Seeds were placed to desiccate in a room at ambient relative humidity, and temperature > 21 °C, with seeds being sampled every two days. Parent tree and seed size affected almost all seed variables and the onset of starch gelatinization, with larger values for larger seeds. Parent tree also affected seedling growth, with larger values for the Type-1. Desiccation time negatively affected the majority of the studied variables. Respiration decreased with desiccation time, with greater values for larger seeds. Our results suggest that practices such as direct seeding could be enhanced by proper parent tree and seed size selection, since those variables could delay the deleterious effects of desiccation. Starch thermal properties also proved to be indicators in tracking metabolic alterations during desiccation.