Water content dynamics of achene, pericarp and embryo in sunflower: associations with achene potential size and dry-down

RONDANINI,D.P.; MANTESE, A.I.; SAVIN, R.; HALL, A.J.

EUROPEAN JOURNAL OF AGRONOMY

Elsevier Science B.V.

Lugar: Amsterdam; Año: 2009 vol. 30 p. 52 - 63

1161-0301

The post-anthesis dynamics of the water content of whole sunflower achene and its major parts (pericarp,embryo) were examined for seven genotypes that spanned a broad range of final achene size(30–100mgachene−1). Objectives were: (i) to establish the relative contributions of pericarp and embryoto whole-achene water content dynamics, (ii) to determine the relationship between maximum watercontent of the pericarp and final achene size, and (iii) to examine the effect of final achene size (as affectedby genotype and environment) on achene dry-down dynamics after physiological maturity (=maximumachene weight). Four experiments were conducted over 2 years under field and glasshouse conditions.Across genotypes and growth conditions, whole-achene and pericarp water contents peaked earlier andmore sharply during grain filling (ca. 35% of grain filling duration, or 30% of final achene weight), maximumembryo water content was achieved somewhat later and declined less sharply. Although thepericarp was a minor (17–35%) component of final achene dry weight, it contained 65–70% of achenemaximum water content. Absolute pericarp water content did not fall to values close to those of theembryo until after physiological maturity. Final achene and embryo dry weights were closely (r2 0.90and 0.85, respectively) associated with maximum pericarp water content. After maximum achene watercontent, rates of whole-achene dry-down were linear (ca. 1.35% d−1), and absolute rates of water lossper achene (range = 1.1–3.7mgH2Oachene−1 d−1) were strongly associated with achene maximum watercontent and final achene dry weight (r2 0.86 and 0.75, respectively). Excluding the inbred line HA89, theremaining genotypes achieved harvest (17%) and storage (11%) achene water concentrations at about 15and 20 d, respectively, after physiological maturity, largely because absolute rates of achene water lossincreased with achene size.We conclude that the pericarp is the dominant component of whole-achenewater content dynamics, and that pericarp and achene maximum water contents are good indicators ofpotential final achene and embryo sizes and achene dry-down rates. Present results also provide a firstapproximation to the quantification of post-physiological maturity dry-down in this crop.© 2008 Elsevier B.V. All rights reserved