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M Tollenaar - One of the best experts on this subject based on the ideXlab platform.
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dissection of physiological processes underlying grain yield in maize by examining genetic improvement and heterosis
Maydica, 2006Co-Authors: M TollenaarAbstract:Maize (Zea mays L.) grain yield in the USA has increased by about 100 kg ha-1 year-1 or 2% year-1 from the start of large-scale adoption of hybrids by maize growers in the late 1930s until the first decade of the 21st century and about 75% of the yield improvement has been attributed to genetic gain. Yield improvement has been associated with increased stress tolerance and het- erosis, but the nature of the enhanced stress tolerance re- mains elusive and heterosis does not appear to be related to rate of yield improvement per se since the introduction of commercial hybrids. Yield improvement is the result of changes in underlying physiological processes and we have examined the physiological component processes that are associated with genetic gain and heterosis in maize. Changes in two important processes appear to be involved in both genetic improvement in grain yield and in yield differences between hybrids and their parental in- bred lines. First, sustaining leaf photosynthesis during the grain-filling period appears to be a major contributor to increases in Dry Matter Accumulation. Second, increased partitioning to the kernels during the sensitive period of kernel number determination appeared to be the major factor in the increase in kernel number. Two 'processes' that have influenced genetic improvement and heterosis differently are maximum leaf area per plant and harvest index. Genetic gain is not associated with a change in harvest index because the increase in kernel number and the increase in Dry Matter Accumulation during the grain- filling period have been proportional, whereas in hetero- sis the increase in kernel number is much greater relative to increase in Dry Matter Accumulation during the grain- filling period.
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development of redroot pigweed is influenced by light spectral quality and quantity
Crop Science, 2002Co-Authors: Irena Rajcan, Clarence J Swanton, Majid Aghaalikhani, M TollenaarAbstract:Light quantity (photosynthetic photon flux density, PPFD) and quality (red:far-red ratio, R:FR) may affect phenological development of weed species growing under a crop canopy. An indoor study was conducted to quantify the effects of incident PPFD and R:FR on development and Dry Matter Accumulation of redroot pigweed (Amaranthus retroflexus L.). Pigweed was grown in growth cabinets from the one-leaf stage to the initiation of seed set under three different PPFD/R:FR treatments: (i) high PPFD (550 μmol m -2 s -1 ) and high R:FR (1.4) (HH), (ii) low PPFD (180 μmol m -2 s -1 ) and high R:FR (1.4) (LH), and (iii) low PPFD (180 μmol m -2 s -1 ) and low R:FR (0.8) (LL). The experiment was undertaken at 12- and 16-h daylengths with three replications. Rate of leaf appearance (RLA) was accelerated with an increase in PPFD (HH vs. LH) at both daylengths. The FR enrichment (LL) negated the effect of low PPFD on RLA under the 12-h but not under the 16-h daylength. Low PPFD delayed the occurrence of floral primordia, flowering and initiation of seed set. Plant height was a result of the complementary effects of PPFD and R:FR. Total Dry Matter Accumulation and partitioning, with the exception of Dry Matter Accumulation to the stem, were influenced by PPFD only. Results of this study show that both light quality and quantity influence the phenology of pigweed.
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source sink ratio and leaf senescence in maize i Dry Matter Accumulation and partitioning during grain filling
Field Crops Research, 1999Co-Authors: Irena Rajcan, M TollenaarAbstract:Abstract Whether the stay-green characteristic of recent maize hybrids is related to a larger source : sink ratio and/or a more efficient use of N during reproductive development was studied in a 3-year field experiment. The experiment was conducted with two short-season maize hybrids, Pride 5 (old) and Pioneer 3902 (recent), grown at two soil-N levels and with source : sink treatments during grain filling ranging from partial defoliation to no grain. Results confirmed that greater Dry Matter Accumulation of Pioneer 3902, relative to Pride 5, was associated with greater leaf longevity. Change in stover weight from silking to maturity an indicator of the difference in supply and demand of assimilates during grain filling, varied from −30% with defoliation to +25% for the no sink treatment. The change was always greater in the new hybrid, indicating that the old hybrid was more source limited. Number of green leaves, an indicator of leaf longevity, was greatest when supply and demand of assimilates during grain filling were approximately equal. Leaf longevity was enhanced by an increase in soil N and the effect was larger in the high source : sink treatments, but differences in leaf longevity between the two hybrids were not influenced by soil-N level. In conclusion, increased leaf longevity of a new relative to an old hybrid was associated with a larger source : sink ratio during grain filling.
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effect of corn induced shading on Dry Matter Accumulation distribution and architecture of redroot pigweed
Weed Science, 1993Co-Authors: Stephane M Mclachlan, M Tollenaar, Clarence J Swanton, Stephan F WeiseAbstract:A fundamental component of modeling crop interference is the effect of understory photosynthetic photon flux density (PPFD) on weed architecture and growth. The effect of decreased PPFD on spaced redroot pigweed Dry Matter Accumulation, distribution, and plant architecture was quantified by increasing corn density and delaying weed planting date. As canopy-transmitted PPFD declined, total Dry Matter Accumulation decreased and relative Dry Matter distribution was greater to main- stem components than to branch components. Increased rectangularity in understory weed architecture was associated with a concomitant decrease in branch num- ber. The proportion of leaf area and Dry Matter in the upper segment of the redroot pigweed increased as PPFD declined with increased corn density. Results suggest that changes in plant architecture, as influenced by canopy- transmitted PPFD, may be as important as those of total Dry Matter and leaf area when describing and predicting the effects of crop-weed interference. Nomenclature:
Juan Jose Guiamet - One of the best experts on this subject based on the ideXlab platform.
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effects of the stay green genotype ggd1d1d2d2 on leaf gas exchange Dry Matter Accumulation and seed yield in soybean glycine max l merr
Annals of Botany, 2001Co-Authors: Virginia Martha Cristina Luquez, Juan Jose GuiametAbstract:Abstract The homozygous combination of the recessive mutations d1 and d2, i.e.d1d1d2d2 , causes retention of chlorophyll, chlorophyll-binding proteins and Rubisco in senescing leaves of soybean (Glycine max L. Merr.). Together with G(a gene that preserves only chlorophyll in the mature seed coat), d1d1d2d2 prolonged photosynthetic activity and increased seed yield in growth chamber experiments. The objective of this work was to test the effects of GGd1d1d2d2(abbreviated to Gd1d2) on leaf gas exchange, growth and seed yield in soybean plants cultured outdoors during the normal growing season. Despite preservation of the photosynthetic machinery in Gd1d2, photosynthesis during the seed filling period was similar in Gd1d2 and its near-isogenic wild type line ‘Clark’. The main factor limiting photosynthesis in the mutant appeared to be stomatal conductance, which was substantially lower in Gd1d2 than in ‘Clark’. In Gd1d2 the rate of Dry Matter Accumulation during the seed filling period was similar or lower than in the wild type. At maturity, Gd1d2 had fewer nodes, fruiting nodes, fruits and seeds per plant, and therefore its seed yield was reduced by 10–20% compared to ‘Clark’. Thus, pleiotropic effects of G, d1 and/or d2 affecting stomatal conductance and seed number appear to be major limitations to the yield potential of Gd1d2. These pleiotropic effects suggest thatG , d1 and/or d2 have regulatory functions in addition to the control of chloroplast disassembly during senescence.
Virginia Martha Cristina Luquez - One of the best experts on this subject based on the ideXlab platform.
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effects of the stay green genotype ggd1d1d2d2 on leaf gas exchange Dry Matter Accumulation and seed yield in soybean glycine max l merr
Annals of Botany, 2001Co-Authors: Virginia Martha Cristina Luquez, Juan Jose GuiametAbstract:Abstract The homozygous combination of the recessive mutations d1 and d2, i.e.d1d1d2d2 , causes retention of chlorophyll, chlorophyll-binding proteins and Rubisco in senescing leaves of soybean (Glycine max L. Merr.). Together with G(a gene that preserves only chlorophyll in the mature seed coat), d1d1d2d2 prolonged photosynthetic activity and increased seed yield in growth chamber experiments. The objective of this work was to test the effects of GGd1d1d2d2(abbreviated to Gd1d2) on leaf gas exchange, growth and seed yield in soybean plants cultured outdoors during the normal growing season. Despite preservation of the photosynthetic machinery in Gd1d2, photosynthesis during the seed filling period was similar in Gd1d2 and its near-isogenic wild type line ‘Clark’. The main factor limiting photosynthesis in the mutant appeared to be stomatal conductance, which was substantially lower in Gd1d2 than in ‘Clark’. In Gd1d2 the rate of Dry Matter Accumulation during the seed filling period was similar or lower than in the wild type. At maturity, Gd1d2 had fewer nodes, fruiting nodes, fruits and seeds per plant, and therefore its seed yield was reduced by 10–20% compared to ‘Clark’. Thus, pleiotropic effects of G, d1 and/or d2 affecting stomatal conductance and seed number appear to be major limitations to the yield potential of Gd1d2. These pleiotropic effects suggest thatG , d1 and/or d2 have regulatory functions in addition to the control of chloroplast disassembly during senescence.
Irena Rajcan - One of the best experts on this subject based on the ideXlab platform.
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development of redroot pigweed is influenced by light spectral quality and quantity
Crop Science, 2002Co-Authors: Irena Rajcan, Clarence J Swanton, Majid Aghaalikhani, M TollenaarAbstract:Light quantity (photosynthetic photon flux density, PPFD) and quality (red:far-red ratio, R:FR) may affect phenological development of weed species growing under a crop canopy. An indoor study was conducted to quantify the effects of incident PPFD and R:FR on development and Dry Matter Accumulation of redroot pigweed (Amaranthus retroflexus L.). Pigweed was grown in growth cabinets from the one-leaf stage to the initiation of seed set under three different PPFD/R:FR treatments: (i) high PPFD (550 μmol m -2 s -1 ) and high R:FR (1.4) (HH), (ii) low PPFD (180 μmol m -2 s -1 ) and high R:FR (1.4) (LH), and (iii) low PPFD (180 μmol m -2 s -1 ) and low R:FR (0.8) (LL). The experiment was undertaken at 12- and 16-h daylengths with three replications. Rate of leaf appearance (RLA) was accelerated with an increase in PPFD (HH vs. LH) at both daylengths. The FR enrichment (LL) negated the effect of low PPFD on RLA under the 12-h but not under the 16-h daylength. Low PPFD delayed the occurrence of floral primordia, flowering and initiation of seed set. Plant height was a result of the complementary effects of PPFD and R:FR. Total Dry Matter Accumulation and partitioning, with the exception of Dry Matter Accumulation to the stem, were influenced by PPFD only. Results of this study show that both light quality and quantity influence the phenology of pigweed.
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source sink ratio and leaf senescence in maize i Dry Matter Accumulation and partitioning during grain filling
Field Crops Research, 1999Co-Authors: Irena Rajcan, M TollenaarAbstract:Abstract Whether the stay-green characteristic of recent maize hybrids is related to a larger source : sink ratio and/or a more efficient use of N during reproductive development was studied in a 3-year field experiment. The experiment was conducted with two short-season maize hybrids, Pride 5 (old) and Pioneer 3902 (recent), grown at two soil-N levels and with source : sink treatments during grain filling ranging from partial defoliation to no grain. Results confirmed that greater Dry Matter Accumulation of Pioneer 3902, relative to Pride 5, was associated with greater leaf longevity. Change in stover weight from silking to maturity an indicator of the difference in supply and demand of assimilates during grain filling, varied from −30% with defoliation to +25% for the no sink treatment. The change was always greater in the new hybrid, indicating that the old hybrid was more source limited. Number of green leaves, an indicator of leaf longevity, was greatest when supply and demand of assimilates during grain filling were approximately equal. Leaf longevity was enhanced by an increase in soil N and the effect was larger in the high source : sink treatments, but differences in leaf longevity between the two hybrids were not influenced by soil-N level. In conclusion, increased leaf longevity of a new relative to an old hybrid was associated with a larger source : sink ratio during grain filling.
Benedito Gomes Dos Santos Filho - One of the best experts on this subject based on the ideXlab platform.
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leaf gas exchange chloroplastic pigments and Dry Matter Accumulation in castor bean ricinus communis l seedlings subjected to salt stress conditions
Industrial Crops and Products, 2008Co-Authors: Hugo Alves Pinheiro, Jose Vieira Silva, Lauricio Endres, Vilma Marques Ferreira, Celene De Albuquerque Câmara, Fabio Felix Cabral, Jaqueline Figueredo De Oliveira, Lucio Wagner Torres De Carvalho, Joao Messias Dos Santos, Benedito Gomes Dos Santos FilhoAbstract:Abstract Brazilian castor bean ( Ricinus communis L) crops have expanded towards semiarid lands, in which soil salinity is an important factor limiting plant development. In order to evaluate the effects of salt stress on leaf gas exchange, pigments, and Dry Matter Accumulation of seedlings, seeds of castor bean var. BRS Nordestina were planted in 15-L pots filled with 13 kg of soil (control) or with soil plus 2 g NaCl kg −1 soil corresponding to 30 mM NaCl (salt treatment). Seedlings were grown under greenhouse conditions and the effects of salinity were assessed by measuring physiological parameters at 38 and 59 days after germination. Salt treatment induced decreases in leaf water potential at pre-dawn ( ψ pd , 42%), stomatal conductance to water vapor ( g s , 36%), and net carbon assimilation rate ( A , 24%) only at 38 days after germination. At the same time, the values for transpiration rate were unchanged and the hydraulic conductance was increased (34%). After 59 days under hypersalinity, leaf ψ pd increased to −0.44 MPa, although g s , A , transpiration rate, and hydraulic conductance were not different between treatments. Salt stress effects on chlorophyll a , chlorophyll b and chlorophyll a + b contents were evident only on experimental day 59. The Dry Matter Accumulation of leaves, roots and stems, as well as the total Dry Matter, and the root to above ground ratio increased with plant growth in both treatments, however, these parameters were lowered in salt-stressed seedlings. In short, all physiological variables were more drastically affected after 38 days under high salinity, and despite acclimatization of A after 59 days exposure to salt, no recovery of the Dry Matter Accumulation was observed in the seedlings, suggesting that this species does not tolerate salt stress at its initial growth stages.
