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Pericarp Damage in Seed Corn

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Pericarp Damage in Seed Corn Pericarp Damage in Seed Corn Introduction: The pericarp of a corn kernel is maternal tissue surrounding the embryo sac and nutritive tissues. It has a vascular connection into the corn cob so nutrients from photosyn- thesis can be supplied to the developing embryo and endosperm. Once seeds reach physiological CONTACT US: 605.692.2758 maturity an abscission layer is formed, “black 236 32nd Avenue [email protected] layer”, which blocks the vascular tissue. As the LABS, INC. Brookings, SD 57006 www.SoDakLabs.com www.SoDakLabs.com seed dries, the pericarp adheres tightly around the endosperm and embryo. Some hybrids lose the pedicel tip upon shelling and may expose Pericarp Damage in Seed Corn Endosperm the black layer (Figure 1.). Some kernels, which INTRODUCTION Pericarp Damage in Seed Corn Introduction: The pericarp of a corn kernel is are shelled, while too moist may have tears in The pericarp of a corn kernel is maternal tissue Plumule/ maternal tissue surrounding the embryo sac and coleoptile area surrounding the embryo sac andnutritive nutritive tissues. tissues. It has a Itvascular connection Scutellum the pedicel area of the pericarp. Impacts and has a vascular connection into theinto corn the corn cob cob so so nutrientsnutrients from photosyn- depression Mesocotyl from photosynthesis can be suppliedthesis can to be the supplied developing to the developing embryo abrasion to the dried seed may cause breaks in the pericarp. To help identify pericarp damage,and endosperm.dry seeds Once seedsare reach submerged physiological in a con- embryo and endosperm. Once seeds reach physiological Root meristem maturity an abscission layer is formed, “black area trasting dye which penetrates cracks, after 30 seconds seeds are removed,maturity rinsed, an abscission dried layer and is formed, layerevaluated.”, which this blocks is knownthe vascular as tissue. As the Black Layer zone the “black layer”, which blocks theseed vascular dries, the pericarp tissue. adheres As tightly around Pedicel tip the seed dries, the pericarp adheresthe endosperm tightly and around embryo. the Some hybrids lose Definitions: the pedicel tip upon shelling and may expose endosperm and embryo. Some hybridsthe black layerlose (Figure the pedicel1.). Some kernels,tip whichFIGURE 1. Photo of a corn kernels with structure identified. Black layer – abscission layer between embryo and pedicel tip. upon shelling which may exposeare the shelled, black while layer too moist (Figure may have tears in 2B.). Shelling corn with high moisturethe pedicel may area causeof the pericarp. tears Impacts and A) B) in the pedicel area of the pericarp.abrasion Other to the areas dried seedof the may cause breaks in the pericarp. To help identify pericarp damage, dry seeds are submerged in a con- trasting dye which penetrates cracks, after 30 seconds seeds are removed, rinsed, dried and evaluated. Coleoptile – protective covering over plumule leaves that aids in shootpericarp emergence. can be damaged due to impacts and abrasions Definitions: during handling and seed conditioning. Rounds can be Embryonic axis – small plant (root, meristem, scutellum and shoot tissue)susceptible to damage due to theBlack plumule layer – abscission being layermore between embryo and pedicel tip. Raised plumule exposed or even a raised surface.Coleoptile (Figure – protective 2). Because covering over plumule leaves that aids in shoot emergence. Protruding embryo – certain hybrids or seed sizes may have an embryonicthe plumule axis that is less protrudes protected severe andEmbryonic damage exposes axis – small can plant occurthe (root, axis meristem, scutellum and shoot tissue) due to impacts and often correlatesProtruding to a seedlingembryo – certain with hybrids a or seed sizes may have an embryonic axis that protrudes and exposes the axis to mechanical impacts. Often causing damaged rated as severe and maydamaged cause coleoptile, a seedling growing with pointsto mechanicala and/ordamaged impacts. shredding Often coleop- causing damaged rated as severe and may cause a seedling with a damaged coleop- tile, damage to growing points and/or shredding to embryonic leaves. tile, damage to growing points and/or shredding to embryonic leaves. of the embryonic leaves. The seed corn industry is expanding the use of plant dessication to reduce the occurance of raised plumules. Figure 1. Photo of a corn kernels with structureFIGURE identified. 2. A) Raised plumule, B) Black layer exposed Figure 2. Protruding plumule and damage to pericarp over coleoptile. DEFINITIONS Figure 3. Brackets depict damage rating A) No Damage B) Slight Figure 1. Photo of a corn kernels with structure identified. regions of seed, embryo margin and over Black layer: abscission layer betweenembryonic embryo axis. A)and None: pedicel no visible tip. dam- age to pericarp covering, B) Slight: tearing Figure 2. Protruding plumule and damage to pericarp over coleoptile. Coleoptile: protective covering overof pericarp plumule area extending leaves up thatless than 25% length of embryo pericarp margin/ aids in shoot emergence throughedge, soil. C) Medium: tearing of pericarp ex- Figure 3. Brackets depict damage rating Embryonic axis: tending up to 50% of length of embryo small plant (root,pericarp meristem, margin/edge scutellum and D) Severe – regions of seed, embryo margin and over and shoot tissue). cracks over the embryonic axis and major breaks in seed or missing parts of the seed. C) Medium D) Severe embryonic axis. A) None: no visible dam- Raised embryo: certain hybrids or seed sizes may have age to pericarp covering, B) Slight: tearing an embryonic axis that is raised and exposes the axis to mechanical impacts. of pericarp area extending up less than 25% length of embryo pericarp margin/ TESTING edge, C) Medium: tearing of pericarp ex- To help identify pericarp damage, dry seeds are submerged in a contrasting dye which penetrates any tending up to 50% of length of embryo cracks in the pericarp, after one-minute seeds are FIGURE 3. A) None: no visible damage to pericarp covering, B) Slight: tearing of pericarp area extending up less than 25% removed, rinsed, dried and evaluated. Categories range pericarp margin/edge and D) Severe – length of embryo pericarp margin/edge, C) Medium: tearing from no damage to severe based on where the pericarp cracks over the embryonic axis and major of pericarp extending up to 50% of length of embryo pericarp tearing, or cracking occurs. margin/edge and D) Severe: cracks over the embryonic axis breaks in seed or missing parts of the seed. and major breaks in seed or missing parts of the seed..
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