Intra-specific competition in maize: Ear development, flowering dynamics and kernel set of early-established plant hierarchies

PAGANO, E.; CELA, S.; MADDONNI, G.A.; OTEGUI, M.E.

FIELD CROPS RESEARCH

Elsevier

Lugar: Amsterdam; Año: 2007 vol. 102 p. 198 - 209

0378-4290

Maize canopies with a synchronous seedling emergence and a uniform plant spatial distribution exhibit early-established plant hierarchies (at the 4-leaf stage; V4). The dominant and dominated individuals of the stand differ in plant growth rate during both the pre-silking period (i.e. from V7 to V13; PGRPS) and the period around silking (i.e. a 30 d period centered in silking; PGRS), and in the ear growth rate around silking EGRS). Based on the depleted availability of assimilates of the dominated plants, we tested the hypotheses that (i) the low PGRPS of  dominated individuals affects the morphogenesis of the apical ear leading to a low number of completely developed flowers per ear, and (ii) the low EGRS of dominated individuals results in a pronounced asynchrony of flowering dynamics and uneven silk exsertion from the husks. Two hybrids with contrasting tolerance to crowding stress (DK752 and DK765 as the tolerant and the intolerant hybrid, respectively) were cropped under different intensities of interplant competition (6, 12, 12 plants m2 thinned to 6 plants m2 at V9 and 6 plants m2 shaded from V9 onwards) during 2004/2005 and at 12 plants m2 during 2005/2006 at Pergamino (348560S 608340W), Argentina. Dominant plants were the individuals of the stands with the highest PGRPS (ca. 1.72 and 2.56 g d1 for dominated and dominant plants, respectively), PGRS (ca. 3.05 and 3.94 g d1 for dominated and dominant plants, respectively) and EGRS (ca. 1.06 and 1.55 g d1 for dominated and dominant plants, respectively). This plant type also exhibited the most synchronous flowering dynamics (anthesis–silking interval ca. 1.49 and 1.15 days for dominated and dominant plants, respectively) and the highest kernel set (ca. 401 and 572 kernels plant1 for dominated and dominant plants, respectively). Apical ears of dominated plants exhibited a delayed in the rate of progress to successive floral stages, but the final number of completely developed flowers per ear did not differ between extreme plant types (ca. 967 and 803 completely developed flowers per ear for DK752 and DK765, respectively). Hence, kernel number per plant was not limited by the number of completely developed flowers per ear, but flowering dynamics were a decisive factor in kernel set of both plant types. Asynchronous silking within the ear of dominated plants determined a greater proportion of flowers per ear with non-exposed silks on silking + 5 d and a larger asynchrony in silk extrusion within the ear. These responses increased kernel abortion rate respect to figures obtained for dominant individuals.4). The dominant and dominated individuals of the stand differ in plant growth rate during both the pre-silking period (i.e. from V7 to V13; PGRPS) and the period around silking (i.e. a 30 d period centered in silking; PGRS), and in the ear growth rate around silking EGRS). Based on the depleted availability of assimilates of the dominated plants, we tested the hypotheses that (i) the low PGRPS of  dominated individuals affects the morphogenesis of the apical ear leading to a low number of completely developed flowers per ear, and (ii) the low EGRS of dominated individuals results in a pronounced asynchrony of flowering dynamics and uneven silk exsertion from the husks. Two hybrids with contrasting tolerance to crowding stress (DK752 and DK765 as the tolerant and the intolerant hybrid, respectively) were cropped under different intensities of interplant competition (6, 12, 12 plants m2 thinned to 6 plants m2 at V9 and 6 plants m2 shaded from V9 onwards) during 2004/2005 and at 12 plants m2 during 2005/2006 at Pergamino (348560S 608340W), Argentina. Dominant plants were the individuals of the stands with the highest PGRPS (ca. 1.72 and 2.56 g d1 for dominated and dominant plants, respectively), PGRS (ca. 3.05 and 3.94 g d1 for dominated and dominant plants, respectively) and EGRS (ca. 1.06 and 1.55 g d1 for dominated and dominant plants, respectively). This plant type also exhibited the most synchronous flowering dynamics (anthesis–silking interval ca. 1.49 and 1.15 days for dominated and dominant plants, respectively) and the highest kernel set (ca. 401 and 572 kernels plant1 for dominated and dominant plants, respectively). Apical ears of dominated plants exhibited a delayed in the rate of progress to successive floral stages, but the final number of completely developed flowers per ear did not differ between extreme plant types (ca. 967 and 803 completely developed flowers per ear for DK752 and DK765, respectively). Hence, kernel number per plant was not limited by the number of completely developed flowers per ear, but flowering dynamics were a decisive factor in kernel set of both plant types. Asynchronous silking within the ear of dominated plants determined a greater proportion of flowers per ear with non-exposed silks on silking + 5 d and a larger asynchrony in silk extrusion within the ear. These responses increased kernel abortion rate respect to figures obtained for dominant individuals. Keywords: Maize; Intra-specific competition; Plant hierarchies; Ear development; Flowering dynamicsMaize; Intra-specific competition; Plant hierarchies; Ear development; Flowering dynamics