Migration of Oil Bodies in Embryo Cells during Acquisition of Desiccation Tolerance in Chemically Defoliated Corn (Zea mays L.) Seed Production Fields

Ashley N Dean,Katharina Wigg,Susana A Goggi,Jeremy Johnson,Erik J Christian,Everton V Zambiazzi,Aaron Schwarte,Edgar Cabrera

doi:10.3390/agriculture11020129

Abstract

Chemical defoliation of seed corn production fields accelerates seed maturation and desiccation and expedites seed harvest. Early seed harvest is important to minimize the risk of frost damage while in the field. This newly adopted seed production practice also allows seed companies to plan harvest and manage dryer space more efficiently. However, premature defoliation may interfere with the migration of oil bodies within embryo cells during desiccation and affect seed germination and vigor. The objective of this study was to investigate the effect of chemical defoliation on the migration patterns of oil bodies within embryo cells during desiccation. Chemically defoliated and non-defoliated plants from five commercial hybrid seed corn fields were sampled in 2014 and 2015. Whole ears with husks were harvested before and after defoliant application at 600 g H2O kg−1 fresh weight (fw), and weekly thereafter until seed reached approximately 300–350 g H2O kg−1 fw. Ten embryos extracted from center-row seeds were fixed to stop metabolic processes, then sliced, processed, and photographed using scanning transmission electron microscopy. The oil bodies within embryo cells followed normal migration patterns according to seed moisture content, regardless of defoliation treatment. Seed germination and vigor were verified and were not significantly affected by defoliation. Chemical defoliation is a viable production practice to accelerate seed corn desiccation and to manage harvest and seed dryer availability more efficiently without negatively affecting seed germination and vigor.

Highlights

Seed corn (Zea mays L.) is harvested close to physiological maturity and dried artificially in specialized seed dryers before storage
Sampling continued until the field was mechanically harvested by the seed company when seed moisture content reached approximately 350–370 g H2O kg−1 fw
S[1e]e.dSpeehdyspiohlyosgiioclaolgpicoatel nptoiatel nistial for this article comprises an active seed metabolic system capable of producing a healthy seedling under a range of environmental conditions in the field. This developmental stage coincides with black layer formation or the formation of callus tissue that marks the end of seed development and severs the connection between the seed and female parent [3]

Summary

Introduction

Seed corn (Zea mays L.) is harvested close to physiological maturity and dried artificially in specialized seed dryers before storage. Physiological maturity is the developmental stage at which seeds reach maximum dry weight [1,2] At this developmental stage, seed moisture content ranges from 300 to 380 g H2O kg−1 fresh weight (fw) depending on the genetic background of the plant and environmental conditions during seed development and maturation [3]. Chemical defoliation expedites harvest by two to five days, widening the harvest window of optimal seed moisture in different hybrid fields. This practice facilitates harvest schedules and management of seed dryer space

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