Study on pecan seed germination influenced by seed endocarp

Area of Science:

• Plant Physiology
• Seed Biology
• Horticulture

Background:

• Freshly harvested pecan (Carya illinoinensis) seeds exhibit nondeep physiological dormancy.
• The pecan seed's endocarp is a significant factor inhibiting germination.

Purpose of the Study:

• To investigate whether the endocarp causes "chemical dormancy" or "mechanical dormancy" in pecan seeds.
• To understand the physical and mechanical properties of the endocarp influencing seed germination.

Main Methods:

• Assessing pecan seed germination after partial or complete endocarp removal.
• Measuring the fracture pressure of the endocarp after soaking in water at various temperatures.
• Analyzing the effect of endocarp integrity on radicle elongation.

Main Results:

• Endocarp removal did not significantly alter germination rates when the kernel remained in contact with the endocarp.
• Preventing endocarp splitting with glue significantly inhibited radicle elongation, suggesting mechanical pressure.
• Endocarp fracture pressure decreased significantly with water uptake but showed little variation with soaking temperature.
• The endocarp exerts mechanical dormancy, likely by pressuring the cotyledon, rather than directly restricting the radicle.

Conclusions:

• The pecan endocarp induces "mechanical dormancy" rather than "chemical dormancy."
• Radicle elongation is influenced by the endocarp's pressure on the cotyledon and its response to suture splitting.