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E J M Kirby - One of the best experts on this subject based on the ideXlab platform.
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factors affecting rate of Leaf Emergence in barley and wheat
Crop Science, 1995Co-Authors: E J M KirbyAbstract:Rate of Leaf Emergence of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) changes with sowing date and temperature and appears to be set early in the plant's life cycle. Four models that advance different hypotheses to explain this variation are examined. None is completely satisfactory, partly because of a nonlinear response to thermal or photothermal time. Soil strength, N nutrition, and depth of sowing affect rate of Leaf Emergence, as may sub-zero temperature or ontogeny. An alternative hypothesis proposes that Leaf Emergence rate depends on daylength and acclimation to temperature. Potential rate of Leaf Emergence may be determined by factors acting on Leaf primordia, which are initiated early in the life cycle
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Co-ordination of stem elongation and Zadoks growth stages with Leaf Emergence in wheat and barley
The Journal of Agricultural Science, 1994Co-Authors: E J M Kirby, M Appleyard, N A SimpsonAbstract:SUMMARYLeaf Emergence, apex development stage, internode length and Zadoks principal growth stage 3 were measured over 3 years at several sites.Internode elongation and Zadoks score were strongly related to the number of emerged culm leaves. The final length of the most basal internode was very variable and contributed to variation in the relationship between Zadoks stage 30 and the number of emerged culm leaves. Variation in the length of the basal internode was related to the final number of culm leaves. Most plants had six culm leaves but the number of leaves was affected by sowing date. In an experiment where sowings were made from September to March, stem elongation and Zadoks stage 30 started at a later stage of apex development in later sowings.Recognition and prediction of culm elongation and number of emerged culm leaves is important for the application of growth regulator and fungicides. Combined with functions to predict the rate of Leaf Emergence and final number of leaves, the relationships described in this paper may enable Zadoks principal growth stage 3 and number of emerged culm leaves to be predicted.
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co ordination of stem elongation and zadoks growth stages with Leaf Emergence in wheat and barley
The Journal of Agricultural Science, 1994Co-Authors: E J M Kirby, M Appleyard, N A SimpsonAbstract:Leaf Emergence, apex development stage, internode length and Zadoks principal growth stage 3 were measured over 3 years at several sites. Internode elongation and Zadoks score were strongly related to the number of emerged culm leaves. The final length of the most basal internode was very variable and contributed to variation in the relationship between Zadoks stage 30 and the number of emerged culm leaves. Variation in the length of the basal internode was related to the final number of culm leaves. Most plants had six culm leaves but the number of leaves was affected by sowing date. In an experiment where sowings were made from September to March, stem elongation and Zadoks stage 30 started at a later stage of apex development in later sowings (.)
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Leaf Emergence tiller growth and apical development of nitrogen dificient spring wheat
Crop Science, 1993Co-Authors: Nancy Longnecker, E J M Kirby, A D RobsonAbstract:Conflicting reports exist about the effect of N supply on the rate of Leaf Emergence. We examined effects of N deficiency on Leaf and tiller Emergence, tiller initiation and apical development in ‘Aroona’ and ‘Gamenya’ spring wheat (Triticum aestivum L.). Four levels of N (e.g., 50 μM N = N₅₀) were supplied by hourly irrigation with complete nutrient solution of plants growing in sand. The control plants in Exp. 1 (N₁₆₀₀) had 64 g kg⁻¹ N intheshoots at the two-Leaf stag e, compared with 33 in N₅₀, 50 in N₃₀₀, and 58 in N₈₀₀. Compared with control plants, dry matter of N₅₀ plants was 10%, N₃₀₀ 50%, and N₈₀₀ 80%. Results in Exp. 2 were similar. The rate of Leaf Emergence was decreased in all N₅₀-treated and some N₂₀₀-treated plants, but not or N₃₀₀-treated plants. Tiller bud initiation was decreased in the treatment. The number of tiller buds was correlated with total number of leaves; if a Leaf emerged, N deficiency did not affect tiller initiation. Nitrogen treatment did not alter the sequence of tiller Emergence, but tiller Emergence was delayed or did not occur in N₅₀, N₂₀₀, and N₃₀₀ plants. Nitrogen treatment had little effect on the rate of apical development. The double-ridge stage of development was delayed ≈2 d for both cultivars at the two lowest N treatments. Terminal spikelet production was also delayed by ≈2 d at these N treatments in Aroona, but not in Gamenya spring wheat. The rate of primordia initiation was decreased in N₅₀ and N₃₀₀ plants, resulting in fewer spikelet primordia. The level of N deficiency affected plant response to the stress.
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co ordination of Leaf Emergence and Leaf and spikelet primordium initiation in wheat
Field Crops Research, 1990Co-Authors: E J M KirbyAbstract:Abstract Leaf Emergence and primordium initiation were measured in experiments done with different varieties in a wide range of environments. Leaf initiation, relative to Leaf Emergence, proceeded at a constant rate. After initiation of the first spikelet, the rate of primodium initiation (primordia per emerged Leaf) changed to a faster, approximately constant, rate which was maintained until initiation of the terminal spikelet. Rate of Leaf initiation (1.7 primordia per emerged Leaf) was similar in all cases analysed. Rate of spikelet initiation varied from about 3.5 to 7 primordia per emerged Leaf, and was negatively correlated with total number of leaves on the shoot, which varied from 7 to 14. A rectangular hyperbola describes the relation between rate of spikelet initiation and total number of leaves. The analysis shows that there is a metrical relationship between different elements of shoot development. A model is given which shows how ear initiation and stem elongation are modulated in shoots with differing total numbers of leaves. The relation between Leaf Emergence and primordium initiation suggests control of apex development by emerging leaves, or vice versa. An accumulation of growing leaves may regulate growth and development of the shoot apex.
E R Marzolf - One of the best experts on this subject based on the ideXlab platform.
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stream ecosystem responses to forest Leaf Emergence in spring
Ecology, 2001Co-Authors: Walter R Hill, Patrick J Mulholland, E R MarzolfAbstract:Streams in deciduous forests undergo marked transitions from light-replete to light-limited ecosystems every spring when leaves emerge on streamside trees. During the course of Leaf Emergence and enlargement, shade from leaves on streamside trees can reduce photosynthetically active radiation (PAR) falling on the streambed from >1000 to <30 Vmol.m-2*s-l. In this study, we examined the effects of Leaf Emergence at multiple levels in two headwater streams in eastern Tennessee. Primary production estimated from both photosynthesis-irradiance measurements of periphyton in the laboratory and whole- steam diurnal oxygen measurements decreased dramatically over the course of canopy closure. Monthly carbon fixation estimates for periphyton in White Oak Creek declined from 354 pg C/cm2 in April to 66 pg C/cm2 in June, while carbon fixation in Walker Branch declined from 495 to 168 pg C/cm2. Periphyton photosynthesis became increasingly efficient at low irradiances (ox increased more than threefold) as ambient streambed irradiances declined, but this increase in efficiency only partially compensated for the photon scarcity caused by riparian shade. Ecological photosynthetic efficiency (percentage of incident PAR energy fixed by photosynthesis) estimated from static models, whole-stream measurements, and ambient PAR was a negative exponential function of incident PAR, increasing from <0.3% to 2% during canopy closure. This increase was attributable to (1) inefficient use of the relatively high irradiances before Leaf Emergence, and (2) greater photoefficiency (increased ox) at low irradiances after Leaf Emergence. Nutrient concentrations (dissolved nitrate and phosphate) in both streams increased coincident with Leaf Emergence, implying a cascade of shade effects through primary producers to abiotic components of the eco- system. Shade effects also propagated to higher trophic levels: growth rates of grazing snails (Elimia clavaeformis) in both streams decreased substantially from April to June, consistent with modeled decreases in the productivity of their food resource (periphyton). Snail growth rates were almost zero in White Oak Creek and were negative in Walker Branch during summer when streambed PAR was lowest. The multilevel effects of Leaf Emergence reported in this study accentuate the importance of light variation in aquatic ecosystems and illustrate the close coupling between streams and their surrounding terres- trial ecosystems.
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Stream ecosystem responses to forest Leaf Emergence in spring
Ecology, 2001Co-Authors: Walter R Hill, Patrick J Mulholland, E R MarzolfAbstract:Streams in deciduous forests undergo marked transitions from light-replete to light-limited ecosystems every spring when leaves emerge on streamside trees. During the course of Leaf Emergence and enlargement, shade from leaves on streamside trees can reduce photosynthetically active radiation (PAR) falling on the streambed from >1000 to
A D Robson - One of the best experts on this subject based on the ideXlab platform.
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Leaf Emergence of spring wheat receiving varying nitrogen supply at different stages of development
Annals of Botany, 1994Co-Authors: Nancy Longnecker, A D RobsonAbstract:Abstract We examined effects of nitrogen (N) supply on Leaf Emergence of spring wheat ( Triticum aestivum L.) grown in sand with nutrient solution containing different N concentrations (9NO 3 : 1NH 4 ). In expt 1, the cultivar 'Gamenya' received nutrient solution twice weekly containing a constant N supply ranging from 50 to 2400 μM N. In expts 2 and 3, cultivars 'Aroona' and 'Gamenya' were irrigated hourly with nutrient solution containing either low (L = 50 μM N) or high (H = 2000 μM N) N supply. In expt 2, the N supply to half of the plants receiving L and H was changed at the double ridge stage of apical development, producing plants receiving LL, LH, HL and HH. In expt 3, N supply was changed firstly when the main stem apex was vegetative (one to two leaves) and secondly when the main stem apex was at double ridge stage (four to five leaves), producing plants receiving LLL, LHL, HLH and HHH. Leaves on the main stem and primary tillers were counted. Rate of Leaf Emergence was estimated from regression of number of leaves against thermal time; the phyllochron was calculated as 1/ rate of Emergence. Severely N-deficient plants (which had at least a 60% reduction in shoot dry weight) had slower rates of Leaf Emergence (expt 1). Fluctuating N supply sometimes, but not always, changed the rate of Leaf Emergence (expts 2 and 3). The N supply before double ridge stage had bigger effects on the phyllochron than that afterwards (expt 3). The phyllocrons of the main stems were generally lower than those of tillers, with a greater difference between stems in N-deficient plants. Low N supply at the vegetative apex stage decreased the total number of leaves on the main stem, while low N supply after double ridge did not.
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Leaf Emergence tiller growth and apical development of nitrogen dificient spring wheat
Crop Science, 1993Co-Authors: Nancy Longnecker, E J M Kirby, A D RobsonAbstract:Conflicting reports exist about the effect of N supply on the rate of Leaf Emergence. We examined effects of N deficiency on Leaf and tiller Emergence, tiller initiation and apical development in ‘Aroona’ and ‘Gamenya’ spring wheat (Triticum aestivum L.). Four levels of N (e.g., 50 μM N = N₅₀) were supplied by hourly irrigation with complete nutrient solution of plants growing in sand. The control plants in Exp. 1 (N₁₆₀₀) had 64 g kg⁻¹ N intheshoots at the two-Leaf stag e, compared with 33 in N₅₀, 50 in N₃₀₀, and 58 in N₈₀₀. Compared with control plants, dry matter of N₅₀ plants was 10%, N₃₀₀ 50%, and N₈₀₀ 80%. Results in Exp. 2 were similar. The rate of Leaf Emergence was decreased in all N₅₀-treated and some N₂₀₀-treated plants, but not or N₃₀₀-treated plants. Tiller bud initiation was decreased in the treatment. The number of tiller buds was correlated with total number of leaves; if a Leaf emerged, N deficiency did not affect tiller initiation. Nitrogen treatment did not alter the sequence of tiller Emergence, but tiller Emergence was delayed or did not occur in N₅₀, N₂₀₀, and N₃₀₀ plants. Nitrogen treatment had little effect on the rate of apical development. The double-ridge stage of development was delayed ≈2 d for both cultivars at the two lowest N treatments. Terminal spikelet production was also delayed by ≈2 d at these N treatments in Aroona, but not in Gamenya spring wheat. The rate of primordia initiation was decreased in N₅₀ and N₃₀₀ plants, resulting in fewer spikelet primordia. The level of N deficiency affected plant response to the stress.
Nancy Longnecker - One of the best experts on this subject based on the ideXlab platform.
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Nitrogen Deficiency Slows Leaf Development and Delays Flowering in Narrow-Leafed Lupin
Annals of Botany, 1997Co-Authors: Qifu Ma, Nancy Longnecker, Miles DracupAbstract:Abstract Effects of nitrogen (N) supply on Leaf and flower development inLupinus angustifoliusL. cv Merrit were examined in a temperature-controlled glasshouse. Low N supply (0.05 or 0.4 m M N) had little effect on Leaf initiation but slowed Leaf Emergence on the main stem compared with plants receiving high N supply (6.0 or 6.4 m M N), or with symbiotic N2-fixation. Plants experiencing transient N deficiency had slower Leaf Emergence than plants with a continuous supply of 6.4 m M N. Nitrogen supply did not affect the time of floral initiation, which occurred within 4 weeks of sowing, by which time nine to ten leaves had emerged. However, the flowering of low-N plants was delayed by 68 to 220 °C d (i.e. 4–14 d) even though they had fewer leaves. The effect of N deficiency on flowering time was largely a result of slower Leaf Emergence.
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Leaf Emergence of spring wheat receiving varying nitrogen supply at different stages of development
Annals of Botany, 1994Co-Authors: Nancy Longnecker, A D RobsonAbstract:Abstract We examined effects of nitrogen (N) supply on Leaf Emergence of spring wheat ( Triticum aestivum L.) grown in sand with nutrient solution containing different N concentrations (9NO 3 : 1NH 4 ). In expt 1, the cultivar 'Gamenya' received nutrient solution twice weekly containing a constant N supply ranging from 50 to 2400 μM N. In expts 2 and 3, cultivars 'Aroona' and 'Gamenya' were irrigated hourly with nutrient solution containing either low (L = 50 μM N) or high (H = 2000 μM N) N supply. In expt 2, the N supply to half of the plants receiving L and H was changed at the double ridge stage of apical development, producing plants receiving LL, LH, HL and HH. In expt 3, N supply was changed firstly when the main stem apex was vegetative (one to two leaves) and secondly when the main stem apex was at double ridge stage (four to five leaves), producing plants receiving LLL, LHL, HLH and HHH. Leaves on the main stem and primary tillers were counted. Rate of Leaf Emergence was estimated from regression of number of leaves against thermal time; the phyllochron was calculated as 1/ rate of Emergence. Severely N-deficient plants (which had at least a 60% reduction in shoot dry weight) had slower rates of Leaf Emergence (expt 1). Fluctuating N supply sometimes, but not always, changed the rate of Leaf Emergence (expts 2 and 3). The N supply before double ridge stage had bigger effects on the phyllochron than that afterwards (expt 3). The phyllocrons of the main stems were generally lower than those of tillers, with a greater difference between stems in N-deficient plants. Low N supply at the vegetative apex stage decreased the total number of leaves on the main stem, while low N supply after double ridge did not.
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Copper supply and the Leaf Emergence rate of spring wheat
Plant and Soil, 1993Co-Authors: Nancy Longnecker, Jenny Slater, Alan RobsonAbstract:Copper deficiency can delay flowering and plant maturity. However, the effect of copper deficiency on the rate of Leaf Emergence has not been quantified. We tested the hypothesis that low copper supply decreases the rate of Leaf Emergence of wheat (Triticum aestivum L. cv Gamenya). Copper foliar sprays are commonly applied to wheat. We examined the response of the rate of Leaf Emergence to a foliar application of copper sulphate.
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Leaf Emergence tiller growth and apical development of nitrogen dificient spring wheat
Crop Science, 1993Co-Authors: Nancy Longnecker, E J M Kirby, A D RobsonAbstract:Conflicting reports exist about the effect of N supply on the rate of Leaf Emergence. We examined effects of N deficiency on Leaf and tiller Emergence, tiller initiation and apical development in ‘Aroona’ and ‘Gamenya’ spring wheat (Triticum aestivum L.). Four levels of N (e.g., 50 μM N = N₅₀) were supplied by hourly irrigation with complete nutrient solution of plants growing in sand. The control plants in Exp. 1 (N₁₆₀₀) had 64 g kg⁻¹ N intheshoots at the two-Leaf stag e, compared with 33 in N₅₀, 50 in N₃₀₀, and 58 in N₈₀₀. Compared with control plants, dry matter of N₅₀ plants was 10%, N₃₀₀ 50%, and N₈₀₀ 80%. Results in Exp. 2 were similar. The rate of Leaf Emergence was decreased in all N₅₀-treated and some N₂₀₀-treated plants, but not or N₃₀₀-treated plants. Tiller bud initiation was decreased in the treatment. The number of tiller buds was correlated with total number of leaves; if a Leaf emerged, N deficiency did not affect tiller initiation. Nitrogen treatment did not alter the sequence of tiller Emergence, but tiller Emergence was delayed or did not occur in N₅₀, N₂₀₀, and N₃₀₀ plants. Nitrogen treatment had little effect on the rate of apical development. The double-ridge stage of development was delayed ≈2 d for both cultivars at the two lowest N treatments. Terminal spikelet production was also delayed by ≈2 d at these N treatments in Aroona, but not in Gamenya spring wheat. The rate of primordia initiation was decreased in N₅₀ and N₃₀₀ plants, resulting in fewer spikelet primordia. The level of N deficiency affected plant response to the stress.
Walter R Hill - One of the best experts on this subject based on the ideXlab platform.
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Effects of riparian Leaf dynamics on periphyton photosynthesis and light utilisation efficiency
Freshwater Biology, 2002Co-Authors: Walter R Hill, Sarah M. DimickAbstract:1. Streambed light regimes change dramatically when riparian trees gain leaves in spring and lose them in autumn. This study examined the effect of these changes on periphyton photosynthetic characteristics, primary production, and light utilisation efficiency in two eastern Tennessee streams. 2. Photosynthesis–irradiance responses were measured at intervals covering Leaf Emergence and abscission in spring and autumn. Photosynthetic efficiency (αchl) increased with declining streambed irradiances during spring Leaf Emergence, but returned to pre-Emergence values after autumn Leaf fall. The onset of photosaturation (Ik) displayed the opposite pattern, decreasing during Leaf Emergence and increasing after Leaf fall. Both αchl and Ik were closely associated (P
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stream ecosystem responses to forest Leaf Emergence in spring
Ecology, 2001Co-Authors: Walter R Hill, Patrick J Mulholland, E R MarzolfAbstract:Streams in deciduous forests undergo marked transitions from light-replete to light-limited ecosystems every spring when leaves emerge on streamside trees. During the course of Leaf Emergence and enlargement, shade from leaves on streamside trees can reduce photosynthetically active radiation (PAR) falling on the streambed from >1000 to <30 Vmol.m-2*s-l. In this study, we examined the effects of Leaf Emergence at multiple levels in two headwater streams in eastern Tennessee. Primary production estimated from both photosynthesis-irradiance measurements of periphyton in the laboratory and whole- steam diurnal oxygen measurements decreased dramatically over the course of canopy closure. Monthly carbon fixation estimates for periphyton in White Oak Creek declined from 354 pg C/cm2 in April to 66 pg C/cm2 in June, while carbon fixation in Walker Branch declined from 495 to 168 pg C/cm2. Periphyton photosynthesis became increasingly efficient at low irradiances (ox increased more than threefold) as ambient streambed irradiances declined, but this increase in efficiency only partially compensated for the photon scarcity caused by riparian shade. Ecological photosynthetic efficiency (percentage of incident PAR energy fixed by photosynthesis) estimated from static models, whole-stream measurements, and ambient PAR was a negative exponential function of incident PAR, increasing from <0.3% to 2% during canopy closure. This increase was attributable to (1) inefficient use of the relatively high irradiances before Leaf Emergence, and (2) greater photoefficiency (increased ox) at low irradiances after Leaf Emergence. Nutrient concentrations (dissolved nitrate and phosphate) in both streams increased coincident with Leaf Emergence, implying a cascade of shade effects through primary producers to abiotic components of the eco- system. Shade effects also propagated to higher trophic levels: growth rates of grazing snails (Elimia clavaeformis) in both streams decreased substantially from April to June, consistent with modeled decreases in the productivity of their food resource (periphyton). Snail growth rates were almost zero in White Oak Creek and were negative in Walker Branch during summer when streambed PAR was lowest. The multilevel effects of Leaf Emergence reported in this study accentuate the importance of light variation in aquatic ecosystems and illustrate the close coupling between streams and their surrounding terres- trial ecosystems.
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Stream ecosystem responses to forest Leaf Emergence in spring
Ecology, 2001Co-Authors: Walter R Hill, Patrick J Mulholland, E R MarzolfAbstract:Streams in deciduous forests undergo marked transitions from light-replete to light-limited ecosystems every spring when leaves emerge on streamside trees. During the course of Leaf Emergence and enlargement, shade from leaves on streamside trees can reduce photosynthetically active radiation (PAR) falling on the streambed from >1000 to