Start Of Stem Elongation Research Articles

Wheat yield potential can be maximized by increasing red to far-red light conditions at critical developmental stages.

Sensing of neighbours via the Red to Far-Red light ratio (R:FR) may exert a cap to yield potential in wheat. The effects of an increased R:FR inside the canopy were studied in dense wheat mini canopies grown in controlled environments by lowering FR. To distinguish between effects exerted by light sensing and assimilate supply, the treatments were complemented with elevated CO2 , applied between different developmental timepoints to specifically impact tillering, spike growth, floret fertility and grain filling, in different combinations. The yield response to high R:FR was strongly dependent on the developmental stage in all three cultivars and pivoted between positive if applied after the start of stem elongation, and negative or null if applied before. Yield gains of up to 70% and 120% were observed, respectively, in two cultivars, associated with a higher number of tiller spikes and grains per spike in the main shoot. The response to the combination of high R:FR and elevated CO2 or CO2 alone were cultivar dependent. Taken together, our results suggest that R:FR exerts a significant control on yield potential in wheat and achieving a high R:FR from stem elongation to maturity is a promising lever towards a significant increase in grain yield.

Architectural Response of Wheat Cultivars to Row Spacing Reveals Altered Perception of Plant Density.

Achieving novel improvements in crop management may require changing interrow distance in cultivated fields. Such changes would benefit from a better understanding of plant responses to the spatial heterogeneity in their environment. Our work investigates the architectural plasticity of wheat plants in response to increasing row spacing and evaluates the hypothesis of a foraging behavior in response to neighboring plants. A field experiment was conducted with five commercial winter wheat cultivars possessing unique architectures, grown under narrow (NI, 17.5 cm) or wide interrows (WI, 35 cm) at the same population density (170 seeds/m2). We characterized the development (leaf emergence, tillering), the morphology (dimension of organs, leaf area index), and the geometry (ground cover, leaf angle, organ spreading, and orientation). All cultivars showed a lower number of emerged tillers in WI compared to NI, which was later partly compensated by lower tiller mortality. Besides, the upper leaf blades were larger in WI. Finally the leaf area index at flowering showed little difference between WI and NI treatments. The rate of leaf emergence and the final leaf number were higher in WI compared to NI, except for one cultivar. Around the start of stem elongation, pseudo-stems were more erect in WI, while around the time of flowering, stems were more inclined and leaves were more planophile. Cultivars differed in their degrees of responses, with one appearing to prospect more specifically within the interrow space in WI treatment. Altogether, our results suggest that altering interrow distance leads to changes in the perceived extent of competition by plants, with responses first mimicking the effect of a higher plant density and later the effect of a lower plant density. Only one cultivar showed responses that suggested a perception of the heterogeneity of the environment. These findings improve our understanding of plant responses to spatial heterogeneity and provide novel information to simulate light capture in plant 3D models, depending on cultivar behavior.

Nutrient stoichiometry in winter wheat: Element concentration pattern reflects developmental stage and weather.

At least 16 nutrient elements are required by plants for growth and survival, but the factors affecting element concentration and their temporal evolution are poorly understood. The objective was to investigate i) element concentration pattern in winter wheat as affected by crop developmental stage and weather, and ii) whether, in the short term, element stoichiometry reflects the type of preceding crop. We assessed the temporal trajectories of element concentration pattern (N, P, K, Ca, Mg, S, Mn, Fe, Cu, Na, Zn) across the life cycle (from seed to seed) of winter wheat field-grown in cool-temperate Sweden during two years with contrasting weather and when cultivated in monoculture or after different non-wheat preceding crops. We found strong influence of developmental stage on concentration pattern, with the greatest deviation from grain concentrations found in plants at the start of stem elongation in spring. Inter-annual differences in weather affected stoichiometry, but no evidence was found for a short-term preceding–crop effect on element stoichiometry. Winter wheat element stoichiometry is similar in actively growing plant tissues and seeds. Nitrogen exerts a strong influence on the concentration pattern for all elements. Three groups of elements with concentrations changing in concert were identified.

Regrowth of spring canola (Brassica napus) after defoliation

Regrowth of dual-purpose canola after grazing is important for commercial success and the aim of this research was to investigate the effects of defoliation on the development, growth, photosynthesis and allocation of carbohydrates. We conducted two pot experiments in which defoliation was conducted at multiple intensities with scissors. Experiment 1 determined changes in flowering date due to defoliation while Experiment 2 investigated the effects of defoliation on growth, photosynthesis and allocation of carbohydrates in canola. Time to the appearance of the first flower was delayed by up to 9 days after the removal of all leaves at the start of stem elongation (GS30), and up to 19 days if the elongating bud was also removed. Stem growth rate decreased by 56–86 % due to defoliation and tap roots did not increase in mass when plants were completely defoliated. Leaf area continued to expand at the same rate as in un-defoliated plants. The new leaf area established per gram of regrowth biomass over 20 days was 158 cm2.g-1 for the complete defoliation treatments compared with 27 cm2.g−1 for the half-defoliated treatment and 13 cm2.g−1 for the un-defoliated treatment. Despite a reduction in total biomass of up to 60 %, the proportion of dry matter partitioned to the leaves was 18 % for all treatments within 20 days after defoliation. Total non-structural carbohydrate levels were reduced rapidly in the stem by day two (predominately sucrose) and the tap root by day four (predominately starch) after defoliation and did not recover to match un-defoliated plant levels within 20 days. Residual leaves on defoliated plants maintained photosynthetic rate compared with the same leaf cohorts on un-defoliated plants in which photosynthetic rate decreased to 39 % by day 12. The rapid recovery of leaf area in defoliated canola was facilitated by the sustained high photosynthetic rate in remaining leaves, rapid mobilisation of stored sugars (stem) and starch (root), and a cessation of root and stem growth.

Assessment of in situ crop LAI measurement using unidirectional view digital photography

This study evaluated the performance of digital photography for measuring the green leaf area index (LAI) and green plant area index (GAI) of field crops by quantifying gap fraction either at nadir or at a 57.5° view angle. Clumping index was estimated using the logarithmic averaging method of Lang and Xiang (1986) to derive the total GAI. Measurement uncertainty associated with foliage inclination and view angles was assessed analytically, as was image classification. The GAI derived for corn, soybean and wheat crops was strongly linearly correlated with the destructive GAI for both the nadir and the 57.5° photographic methods (R2>0.83, root mean square error<0.63). Because the destructive LAI and GAI exhibited strong linear correlations for soybean and corn, LAI could be predicted from photographic methods. The LAI and GAI of the wheat canopy were poorly correlated because of a significant proportion of non-leaf tissues contributing to photosynthesis after the start of stem elongation. Clumping had a greater effect on the nadir photographic method than on the 57.5° method. The effective GAI from nadir viewing was better correlated to the destructive GAI than the photographic GAI, whereas the effective GAI from the 57.5° photographic method provided a greater underestimation of the destructive GAI than the photographic GAI. The extinction coefficient at nadir viewing was found to be 22% larger than the assumed value (i.e. k=0.61 vs. the theoretical value of 0.5). When gap reduction reached the asymptotic saturation level with increasing LAI, higher classification accuracy was required to achieve acceptable LAI measurement accuracy. The 57.5° photographic method was more affected by classification accuracy when LAI was higher than 1.5. With crop canopy development, the decrease in gap size and the decline in signal strength from shadows mean that high-quality photos are required to effectively differentiate gaps from plant tissues.

Tan spot - the most harmful wheat leaf disease in Latvia

Tan spot (&lt;i&gt;Pyrenophora tritici&lt;/i&gt;-&lt;i&gt;repentis&lt;/i&gt;) is one of the most important wheat diseases in Latvia. Significant spreading of this disease was observed from 1998. Field experiments were carried out at the Research and Training Farm "Peterlauki" of the Latvia University of Agriculture, during 1998-2003. Development of diseases was observed on 14 winter wheat varieties, dynamics of development was investigated on 'Donskaja polukarlikovaja' and 'Stava'. Assessments of the disease severity were carried out on the upper three leaves each week from the start of stem elongation to full ripening. Tan spot was observed at the stage of stem elongation in 2003, and only after flowering in 1999. Increase of the disease severity was slow until stage of milk ripeness, and only in late stages of wheat development sharp increase of the disease was observed. Total rate of infection (through the session of vegetation) was very slow (0,01-0,19), but during ripening rate achieved 0,5-0,6. The main reason of so unequal development of the disease seems changes in amount of infection sources. Other possible reason of rapid increase of the disease development is the relationship between leaf age and susceptibility to the disease. Further research is necessary for better understanding of tan spot life cycle.

Appraisal of Micronutrient Impact on Absorption of Macro- and Micronutrients in Tellar Cultivar of Soybean

In order to study the effects of applying the micronutrients zinc, boron, and manganese (which are added to the soil and sprayed on the crop) on the absorption of the macro- and micronutrients in soybean seeds, an experiment was carried out using the factorial design with the two factors of adding the micronutrients zinc, manganese, and boron to the soil and spraying them on the crop, with 16 treatments and four replications (a total of 64 trials). On the basis of the soil test which had been conducted, the required amounts of the micronutrients (40, 30, and 10 Kg.h of zinc sulphate, manganese sulphate, and boric acid, respectively) were added to the soil before seeding. In the spray treatments, zinc and manganese (0.30 %) and boron (0.20 %) were sprayed on the crop at the start of stem elongation a d at flower bud formation. Results of the comparison of the means showed that the highest concentration of nitrogen (6.65 %) and phosphorous (0.18 %) in the seeds were obtained when zinc was sprayed on the crop, the highest potassium concentration in the seeds (0.92 %) was achieved when manganese was added to the soil, and the highest zinc concentration in the seeds (52.5 ppm) was observed when zinc was applied to the soil. These results also indicated that, among the treatments of spraying the micronutrients on the crop, the highest manganese concentration in the seeds (24.77 ppm) was obtained when manganese was sprayed on the crop, that the highest boron concentration in the seeds(46.58 ppm) was achieved when boron was added to the soil (and that this boron treatment had a statistically significant difference with the others). Comparison of the interaction effects of the data showed that the highest seed nitrogen concentration (6.72 %) was observed when zinc was sprayed on the crop, that the highest seed phosphorous concentration (0.22 %) was obtained when boron was added to the soil, that the highest seed potassium concentrations (0.93 % and 0.94 %) were achieved when zinc and manganese were sprayed on the crop, respectively, that the highest seed zinc concentrations were observed by adding manganese to the soil plus spraying zinc on the crop (55.33 ppm) and by adding zinc to the soil plus spraying zinc on the crop(55 ppm), that the highest seed manganese concentration (23.67 ppm) was obtained by adding zinc to the soil plus spraying manganese on the crop or by adding manganese to the soil plus spraying boron on the crop, and, finally, that the highest seed boron concentrations (44 and 41.67 ppm) were achieved by spraying boron on the crop and by adding manganese to the soil plus spraying boron on the crop, respectively.

Field estimation of technological bread-making quality in wheat

The determination of the technological quality of bread wheat ( Triticum aestivum L.) requires a strong investment of time and money on behalf of the flour industry. For this reason, a field experiment was carried out over a 2-year period on a Vertisol under rainfed Mediterranean conditions with the objective of predicting, during the growing season, the technological quality of wheat at harvest with the use of a chlorophyll meter (Minolta SPAD 502). The SPAD meter readings were taken at the start of stem elongation and at anthesis determining the grain yield, alveogram parameters and gluten content at harvest. The chlorophyll meter readings at both growing stages were related to the grain protein content, alveogram index ( W), dough extensibility ( L), tenacity–extensibility ratio ( P/ L) and gluten content values. Dough tenacity ( P) was not related to the readings. The models were validated by the full cross-validation method, showing better reliability at anthesis than stem elongation. The grain yield was correlated separately for each year, due to the influence of rain variability on the grain yield. Under rainfed Mediterranean conditions, the SPAD meter is a very useful tool in predicting the technological quality of bread wheat in advance, eliminating the need for expensive instruments and, above all, reducing the analysis time dedicated to determining the technological quality.

Effects of the application rate and time of the growth regulator trinexapac-ethyl in seed crops of Lolium perenne L. in relation to spring nitrogen rate

To test the effects of the growth regulator trinexapac-ethyl (Moddus 250 EC) in the main seed crop of grasses in the Netherlands, 10 field trials were conducted in perennial ryegrass ( Lolium perenne L.). These field trials were carried out in first and second seed harvest crops during 1999–2002. Four rates of Moddus (untreated, 0.4, 0.8 and 1.6 L product ha −1) were applied at the start of stem elongation (DC 30–31, zero to one node) during the first two years. In addition, the effect of timing of the application of 0.8 L Moddus ha −1 was studied (untreated, DC30–31, DC31–33, DC33–37). In most trials, in addition to the normal amount, 45 kg N ha −1 extra spring nitrogen was applied. The work reported is valuable, and has relevance to all areas of the globe where this perennial ryegrass is grown for seed, e.g., northern Europe, the US (particularly, Oregon), New Zealand, Australia, Chile and Argentina. Crop development in spring was partly affected by weather conditions during the previous autumn and winter, so while Moddus was applied at the same crop development stage, the calendar dates varied for the different harvest years. Temperature sum from 1 November accounted for only 51.4% of the variation. Applications at higher rates increased the reduction of stem length, lodging of the crop and the density of panicles. Application later than DC30–31 resulted in shorter culm length and higher total dry matter weight of the crop. The application of the highest rate of Moddus (1.6 L ha −1) at the crop development stage DC30–31 never resulted in an unacceptable final phytotoxic effect. Effect of Moddus on seed yields was inconsistent; the potential seed yield increase was about 10%. In general, there was no significant interaction between the application of 0.8 L Moddus ha −1 at the crop development stage DC30–31 and the spring nitrogen rate. The results show that DC31–33 is the best time to apply 0.8 L Moddus ha −1. In second seed harvest crops of lawn types applying 0.8 L Moddus ha −1 together with increasing the amount of spring nitrogen can be considered.

Mechanical control of clover improves nitrogen supply and growth of wheat in winter wheat/white clover intercropping

The major objective for clover in a winter wheat/white clover intercropping system is to supply nitrogen (N) for the wheat. A field experiment was repeated in 2 years on a loamy sand in Denmark to investigate the possibilities for increasing N supply to the winter wheat by cutting and mulching the clover between the wheat rows. The clover was cut with a weed brusher on three different dates in each year. Intercropped wheat with unbrushed clover had a lower grain yield than wheat as a sole crop. Brushing increased wheat N uptake and wheat grain yields. Intercropping with two or three brushing dates gave higher wheat yields than wheat as the sole crop. The largest increases in grain N uptake, 21–25 kg N ha −1, were obtained for the brushings around wheat flag leaf emergence. The highest yield increases with a single brushing, 0.98–1.11 Mg DM ha −1, were obtained when brushing was performed during the stem elongation phase. The largest grain yields for treatments with two brushings were obtained with a first brushing at start of stem elongation and a second around flag leaf emergence. The first brushing probably provided N to increase the wheat leaf area index and thus the light interception, while the second brushing provided N to sustain the leaf area during grain filling and reduced clover biomass and therefore competition for water. Intercropping wheat and clover increased grain N concentrations by 0.11–0.39%-point compared with wheat as a sole crop. Intercropping may thus offer possibilities for improving the bread-making quality of organically grown wheat.

EFFECTS OF SOWING TIME ON NITRATE AND TOTAL NITROGEN CONCENTRATIONS IN FIELD-GROWN CANOLA (BRASSICA NAPUS L.) AND IMPLICATIONS FOR PLANT ANALYSIS

Canola was grown in a field experiment in the cropping belt of central New South Wales to determine the effect of sowing time on nitrate-nitrogen (N03-N) and total nitrogen (N) concentrations in relation to assessing the N status of the crop by plant analysis. Plants were sampled at the 5–6 leaf rosette stage (5–6RS), the start of stem elongation (SE), and the start of flowering (SF). The petiole of the youngest mature leaf (YML) was used for determination of NO3-N, and total N concentrations were determined in the YML petiole and lamina and the whole shoot. Critical N concentrations were derived from the relationships between the NO3-N or total N concentrations in these organs and dry-matter production at the time of sampling or seed yield at maturity. Delaying sowing from early to late May reduced nitrate-N concentrations at 5–6RS and SE, and total N concentrations at 5–6RS by about 50% in the YML petiole, but did not reduce total N concentrations to the same extent in the YML lamina or whole shoot (mean reduction for 5–6RS, SE, and SF: 6%). Nitrate-N and total N concentrations in all organs tested declined with plant age, but were similar at each sampling for dry-matter production at the time of sampling and for predicting potential seed yield. Concentrations of both NO3-N and total N in all organs tested were suitable for assessing the N status of young canola plants. After SE, however, the concentration of total N in the whole shoot was a more reliable indicator of plant N status as NO3-N was barely detectable in the YML petiole at SF, and the YML was difficult to identify. Seed yield decreased by 45–50% between the early and late May sowings, but the just-adequate N fertilizer rates (defined as producing 90% of maximum seed yield) were similar (90–93 kg N ha−1) for both sowing times. It was concluded that sowing time and accurate determination of the stage of crop development are important factors in interpreting the results of plant testing based on NO3-N or total N concentrations in canola.

Floral morphogenesis in Rudbeckia hirta in relation to polyamine concentration

Changes in polyamine concentration in the long day (LD) plant Rudbeckia hirta were examined over the course of floral initiation and development. Plants of R. hirta were grown to maturity under 9h, non‐floral‐inductive photoperiods. At maturity, half the plants were placed in ambient day length plus a 4‐h night interruption. Plants were sampled at 0, 4, 8, 12 or 16 days for polyamine content and floral initiation. Polyamines were extracted from fully expanded leaves and the meristems were examined histologically. In another experiment, polyamines were extracted from the meristems under paired LD and short day (SD) conditions every 2 days from 0 to 22 days. A rise in free polyamines was linked to important cytological events during floral initiation. Free putrescine and spermidine levels increased after 4 LD and continued until 14 to 16 LD when the levels in the meristem began to decline. Events of floral initiation began between 4 and 8 LD with cell proliferation and the start of stem elongation. Initiation was irreversible after 14 to 16 LD, the period when putrescine and spermidine began to decline. After 4 LD, the polyamine level was consistently higher in the photoinduced plants. Our results from this study, using direct histological comparisons of meristematic development and polyamine concentration, clearly demonstrate a correlation of polyamines and flowering.

Nucleotide sequence and expression of a novel glycine-rich protein gene from Arabidopsis thaliana

A clone containing a gene coding for a novel glycine-rich protein has been identified in an Arabidopsis thaliana genomic library. The gene codes for a 339 amino acid protein and is interrupted by a 686 bp intervening sequence. The gene is present in one copy only. Transcripts accumulate mainly in hypocotyls and stems and the highest level is observed in rosettes before the start of stem elongation. The protein contains 71% of glycine residues and is highly hydrophobic.

Effect of watertable on yield and root depth of winter wheat in the French West Central Atlantic Marshlands

The watertable in winter depends on the field drainage system and the structural stability of the soils. The yield of winter wheat and the nitrogen supply of the soil are positively correlated with a lower water-table. Therefore, the mean watertable in winter is a good environmental indicator for the yield potentialities For the explanation of yield variations, the depth of the root system was observed at the start of stem elongation and the anthesis. At the start of stem elongation, the root depth (E i) increases with a lower watertable in winter (r = 0.931). The root depth after anthesis (E f) depends on the root depth at stem elongation (E i) and on the climatic balance R (rainfall)-ET (evapotranspiration) between these two stages. For R>ET, R = ET and R<ET, root growth (dE = E f−E i) is respectively almost zero, decreases with increasing E i (“growth of roots making up for lost time”) or increases with increasing E i (“homothetic growth”). The root depth studies explain the relation between the pedoclimatic and environmental conditions and the yield of winter wheat.

Factors influencing the yield and feeding value of pasture grown for conservation

Abstract The growth of ryegrass/clover pasture was monitored for 10 weeks after 3 closing dates in spring. The pasture was closed (a) before the start of stem elongation (Treatment 1; 30 September 1980, 28 September 1981); (b) when the developing meristems were just below defoliation height (Treatment 2; 21 October 1980, 19 October 1981); and (c) when 65–70% of apical meristems were removed (Treatment 3; 12 November 1980, 9 November 1981). Within each treatment, increasing dry matter (DM) yield was accompanied by a decrease in digestibility and crude protein content of the sward during the growth period. Compared with Treatment 1, Treatment 2 did not show a significant decrease in DM production, but the sward which developed under Treatment 2 contained more stem material, and was 3–12 percentage units lower in digestibility throughout the growth period. The digestible dry matter (DDM) yield was reduced by 15–40% with respect to Treatment 1 when the treatments were compared at the same digestibility. At 70% digestibility, Treatment 2 yielded an average of 4.8 t DM/ha per year over both years, compared with a consistent 6.3 t DM/ha per year for Treatment 1. The removal of apical meristems from Treatment 3 at closing produced a more vegetative sward with lower DM and DDM production than Treatments 1 and 2. The production of vegetative leaves in Treatment 3 resulted in a similar digestibility between Treatments 1 and 3 over most of the 1980–81 growth period. However, in 1981–82 the presence of late flowering Cynosurus cris-tatus in the Treatment 3 sward resulted in the production of herbage containing more stem material in the early part of the growth period, and as a consequence, digestibility was reduced. In both years, after about 40 days growth, the completion of floral development in Treatment 3 prevented any subsequent fall in digestibility. The results indicate that early closing and cutting are essential to obtain conserved crops of high quality.

Response to Temperature in a Stand of Pearl Millet (Pennisetum typhoidesS. &amp; H.)

The development of individual tillers in stands of pearl millet was investigated in the glasshouse at mean air temp. of 19, 22, 25, 28 or 31°C. The rate of appearance of individual tillers was similar to that on the main culm but later tillers produced fewer leaves. Apical dissection showed that 2-5 leaf primordia failed to emerge from some tillers; the cessation of development preceded any external signs of premature senescence by 3-4 wk. The concept of thermal time was used to determine when leaf appearance ceased on individual tillers. Tiller development stopped synchronously at c. 430° days in all treatments, indicating that it was related to a common physiological or environmental condition. This period corresponded to the start of stem elongation and closure of the crop canopy

Assessment of a rapid method, using soil cores, for estimating the amount and distribution of crop roots in the field

A study was made of the relationship between the number of roots (Nr) observed on unit area of the freshly exposed, horizontal faces of soil cores, and the amounts of roots (per unit volume) present in the same cores. Soil cores, 7 cm diameter, were extracted to depths of 1 m from cereal crops in 1976 at three field sites located on clay soils. Sampling was either at the start of stem elongation, or at anthesis. Estimates of root length per unit soil volume (L) were derived from Nr by assuming random orientation of roots in the soil.

Gibberellins in Relation to Flowering and Stem Elongation in the Long Day Plant Silene armeria

Two long days induced some flowering and 4 or more long days caused 100% flowering in Silene armeria. On long days microscopically detectable flower primordia were first seen after 6 days, which is at least 1 day before the start of stem elongation. Both gibberellin A(3) and A(7) caused flowering on short days, but the results were variable and flowering was never 100%. Three different gibberellins were detected in Silene extracts. The pattern of gibberellins extracted from plants on short and long days was qualitatively the same, but on long days gibberellin content was up to 100% higher than on short days. Only small amounts of diffusible gibberellins were obtained from Silene shoot tips (including very young leaves) on short days. However, on long days the diffusible gibberellins increased by as much as 10-fold after 4 to 6 long days but then declined somewhat after 10 long days. The gibberellins extracted from the shoot tips at the completion of the diffusion period also increased under long days, although the increase was not as large as for the diffusible gibberellins. An A(5)-like gibberellin present in extracts was not detected in diffusates.Treatment with AMO 1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride) completely inhibited stem elongation on long days but had no effect on flowering. In addition, treatment with AMO 1618 caused at least an 80% decrease in the level of extractable gibberellin, while the diffusible gibberellin was reduced below the limits of detection in the d5 corn bioassay. When endogenous gibberellin levels were suppressed by pretreatment with AMO 1618 on short days, gibberellin A(3) caused more stem elongation in plants moved to long days than in plants left on short days. Thus the sensitivity of Silene plants to gibberellin with respect to stem growth is affected by photoperiod. It is concluded that in Silene endogenous gibberellins are a controlling factor for stem elongation but apparently are not required for flower formation.