Water uptake in germinating pecan (Carya illinoinensis) seed

Water uptake is the fundamental and essential requirement for seed germination. Pecan seed has a hard woody endocarp that plays an important role during water uptake.To explore water uptake during germination, the spatiotemporal pattern of water and effect of the endocarp were analysed using high-field MRI, dye-tracing, wax blocking and SEM of water uptake.Isolated seeds completed water uptake in 8 h while whole seeds required 6 days, hence, cracking the endocarp plays an important role. The hilum is the channel through which water enters the seed, while the remainder of the seed coat consist of cells covered with a waxy layer that act as a barrier to water absorption. The region with the highest water content in pecan seed is the edge of the U-shaped region, and water can progressively diffuse from this U-shaped region into the whole kernel.We report a new water absorption stage between phase II and phase III of the triphasic model of water uptake of pecan seeds. Cracking the endocarp changed water distribution in pecan seeds, which may trigger further water absorption and radicle elongation.

Automated summary

Water uptake is essential for seed germination, and the endocarp of pecan seed plays an important role in this process. Various techniques were used to analyze the spatiotemporal pattern of water uptake and the effect of the endocarp on water absorption. Isolated seeds completed water uptake in 8 hours, while whole seeds required 6 days, indicating the significance of cracking the endocarp. The hilum serves as the entry point for water, while the rest of the seed coat acts as a barrier due to the waxy layer. The U-shaped region of the pecan seed has the highest water content, and water gradually diffuses from this region to the entire kernel. A new stage of water absorption was observed between phase II and phase III of the triphasic model of water uptake in pecan seeds. Cracking the endocarp changes water distribution and may trigger further water absorption and radicle elongation.