Dry Matter Remobilization Research Articles

Stem reserve accumulation and mobilization in wheat (Triticum aestivum L.) as affected by sowing date and N – P – K levels under Mediterranean conditions

Some parts of the dry matter accumulated in the wheat stem during the vegetative period are translocated to grain during the grain-filling period. This study assesses the changes in dry matter accumulation in wheat, and the translocation of different internodes of the main stem as affected by some cultural practices. Field experiments, including 3 sowing dates (early, conventional, and late), and 4 N - P - K levels, F_1 - (0 - 0 - 0), F_2 - (110 - 90 - 80), F_3 - (70 - 50 - 40) and F_4 - (150 - 130 - 120), were conducted at the Agricultural Faculty of Shahid Chamran University during 2008 and 2009. The main stem internodes length, weight, dry matter accumulation, and mobilization were measured. Our results showed that the behaviors of the 4 N - P - K levels were similar as they ranged in the same order for pre-anthesis and post-anthesis dry matter accumulation; also, differences in fertilizer application induced similar changes in dry matter accumulation and remobilization. Dry matter translocation was an average of 2% higher for all fertilized treatments, when compared to the control, which has shown the low influence of fertilization on this efficiency in our study. The effect of sowing dates in pre-anthesis dry matter contribution to reproductive organs was much more than the influence associated with the N - P - K levels. However, we recorded differences in dry matter, mobilization efficiency, and mobilization dry matter among sowing dates. The early sowing dates show the best value for mobilized dry matter and dry matter in all stem internodes. Nevertheless, mobilization efficiency had lowest value at this time. The highest mobilization efficiency in all stem internodes was associated with lowest N - P - K level application; also, mobilized dry matter decreased with increasing fertilizer application with all sowing dates and stem internodes, except with early sowing dates for peduncle internodes. With a delay in sowing date, and/or increase in N - P - K levels, the amount of dry matter remobilization decreased, mainly due to a decrease in stem weight. However, the sowing dates had greater influence on dry matter accumulation and remobilization than the fertilizer application.

Grain yield and quality of winter wheat in different planting patterns under deficit irrigation regimes

Limited water resources restrict winter wheat grain yield and quality in the Huang-Huai-Hai Plain of North China, and establishing optimal planting patterns according to crop water requirements is the key factor for achieving rational water use. In this paper, 4 planting patterns were applied, namely, uniform row (30 cm; traditional pattern), wide (40 cm)-narrow (20 cm) row, furrow (double lines in the furrow with 20 cm spacing, and 40 cm between furrows), and seed bed (double lines on the bed with 20 cm spacing, and 40 cm between beds). Each planting pattern was irrigated twice during the jointing and heading stages, and total irrigation water was controlled at 120 mm. Grain yield was significantly (LSD, P < 0.05) higher in the furrow planting pattern than in the uniform row, wide-narrow row, and seed bed planting patterns, by 73.4, 64.3, and 53.4 g/m<sup>2</sup>, respectively, in 2004–2005 and by 54.3, 42.6, and 30.2 g/m<sup>2</sup>, respectively, in 2005–2006, mainly because of a significant (LSD, P < 0.05) increase in the spike and kernel numbers. These results were caused by changes in the contribution of dry matter remobilization to grain yield (CDMRG); the CDMRG was higher in the furrow planting pattern than in the uniform row, wide-narrow row, and seed bed planting patterns by 5.1%, 4.3%, and 2.9%, respectively. Gliadin and glutenin contents in the furrow planting pattern were 4.67% and 5.85%, respectively, and were significantly (LSD, P < 0.05) higher than those in the uniform row, wide-narrow row, and seed bed planting patterns; however, the furrow planting pattern had no significant (LSD, P < 0.05) effect on albumin and globulin contents. Dough development time (DDT) and dough stable time (DST) in the furrow planting pattern were 5.6 min and 8.8 min, respectively; they were significantly (LSD, P < 0.05) improved compared to those in the uniform row, wide-narrow row, and seed bed planting patterns; however, there were no significant (LSD, P < 0.05) differences in dough breakdown time (DBT) between any of the planting patterns. These results suggest that the furrow planting pattern combined with deficit irrigation during the jointing and heading stages can be applied to winter wheat production in the Huang-Huai-Hai Plain of North China.

Evaluation of yield potential and stress adaptive trait in wheat genotypes under post anthesis drought stress conditions.

Twenty winter wheat genotypes were evaluated under both post-anthesis drought stress and normal conditions in Ardabil Agricultural Research Station in two successive growing seasons 2005 - 2007 using randomized complete block design with three replications. The results showed that there were significant differences between genotypes in stem reserve under both normal and post anthesis drought stress conditions. Post-anthesis drought stress did not affect kernel numbers per spike. The rate of dry matter accumulation by kernels considerably decreased by water deficit. Dry weight of vegetative organs decreased in grain filling period under stress and normal conditions, contrasting anthesis stage. But, the rate of translocated dry matter was much higher in genotypes nos. 14, 15, 16, 18, 19 and 20 under drought stress condition. 1000 GW and weight of kernels per spike were more severely reduced by water deficit. The positive correlation of grain yield with grain weight per spike, 1000 GW, remobilization of dry matter, harvest index and stress tolerance index (STI) and significant negative correlation of grain yield with drought susceptibility index (SSI) revealed that selection must be exercised for high harvest index, grain weight per spike, 1000 GW, remobilization of dry matter and STI in stress condition. The negative correlation of ‘STI’ with ‘SSI’ indicated the efficiency of ‘STI’ as a selection criterion for identifying the drought tolerant with high yield potential in winter wheat genotypes. Key words: Winter wheat, drought stress, dry matter, remobilization.

Grain yield, dry matter accumulation and remobilization, and root respiration in winter wheat as affected by seeding rate and root pruning

Field experiments conducted in 2007/08 and 2008/09 at the Changwu Agricultural Research Station on the Loess Plateau of China comprised three seeding rates (SR1: 225 seeds m −2, SR2: 280 seeds m −2, and SR3: 340 seeds m −2) and two root pruning treatments (W: root pruning in the over-wintering period and S: root pruning at the spring-growth stage), with the un-pruned wheat plants as controls. In the severe drought toward the end of the growing season of 2008, grain yield decreased as the seeding rate increased, but under the more favorable conditions in 2009 the reverse was true. Averaged over the seeding rates, grain yield was significantly increased in both W and S in both years; grain yield and yield components were higher in W; and S recorded the highest water use efficiency. The interaction between seeding rate and root pruning was not statistically significant. Leaf area index (LAI) and tiller density were higher as seeding rates increased whereas in W and S, increased LAI and decreased tillers significantly, but had no effect on fertile tillers. The rate of leaf photosynthesis was lower and root respiration was significantly higher at higher seeding rates, whereas in root pruning treatments, significantly higher leaf photosynthetic rate and lower root respiration were observed. Soil water contents were lower as seeding rate increased. A significant decrease in water use before stem elongation was observed in W, while S consumed less soil water than W and the control over the whole growing season. Post-heading accumulation of dry matter and its remobilization from vegetative parts to the grain was significantly greater at higher seeding rates. Post-heading accumulations of dry matter and grain yield were also significantly greater in W and S than the un-pruned plants, although pruning reduced both dry matter remobilization and its contribution to grain yield. The possibility of reducing the proliferation of roots to increase yields at higher seeding rates and conserving the soil water at different growing stages in water-limited environments is discussed.

Post-anthesis dry matter and nitrogen dynamics in durum wheat as affected by nitrogen and temperature during grain filling

Durum wheat (Triticum turgidum L. var. durum Desf.) is commonly grown in Mediterranean conditions, where temperature stress during grain filling can limit productivity. This research was performed to evaluate the effect of temperature during grain filling on dry matter and nitrogen dynamics in two Italian durum wheat varieties, Appio and Creso, grown with different nitrogen availabilities. The experiment compared two different temperature regimens, one within the normal range occurring during grain filling in Central Italy, the other within the normal range occurring in the southern regions of Italy (20/15 °C and 28/23 °C day/night, respectively). Plants were grown in pots outdoor until anthesis and afterward were placed in growth chambers. Results showed that nitrogen fertilization and post-anthesis temperature affected growth, accumulation and partitioning of dry matter and N in durum wheat which, in turn, modified grain yield and N content. Grain yield was better expressed at 20/15 °C, while grain protein concentration was favoured under the 28/23 °C temperature regime. Higher temperature promoted remobilization of dry matter and restrained current photosynthesis, but reduced grain yield, indicating that the loss of photosynthesis could not compensate for the gain from increased remobilization. Grain N content, on the contrary, was promoted under the higher temperature regime, as high temperature reduced N remobilization but did not inhibit root water and nitrogen uptake, given that no water shortage occur.

Effects of defoliation on grain yield and water use of winter wheat

SUMMARYField and pot experiments were conducted to investigate the effects of defoliation on crop performance and the possibility of using defoliation as a method for conserving soil moisture. The study was conducted during 2006–2008, over two growing seasons of winter wheat (Triticum aestivumL.) in the North China Plain. Three levels of defoliation (mild, moderate and severe) were imposed on winter wheat in the field during the following crop phases and conditions: at heading, at anthesis under water deficit conditions and at anthesis under two or three levels of irrigation. Additional pot experiments with three levels of defoliation under two water regimes were arranged. The results showed that both the intensity of defoliation and the timing of defoliation significantly reduced grain production. Under wet conditions the reduction was over 20%, while under dry conditions the reduction wasc. 12%. Yield reduction was greater for defoliation at heading than at anthesis and it was mainly caused by a reduction in kernel weight. Mild defoliation (top three leaves retained) did not affect grain yield. Moderate defoliation (top two leaves retained) slightly reduced grain production. Root length density in the topsoil profile was significantly reduced by severe defoliation at anthesis under wet conditions, but it increased under dry conditions. Dry matter remobilization to grains under moderate and mild defoliation was increased and resulted in a relatively higher harvest index (HI). The photosynthetic rate of the leaves remaining after defoliation was enhanced under all soil moisture conditions. Although defoliation reduced the seasonal water use (ET), the yield reduction was much greater than the reduction in ET under severe defoliation, resulting in lower water use efficiency (WUE). The results show that conserving soil moisture by removing leaves might not be an economic choice. Under the conditions of the present study, the WUE of winter wheat was not improved by defoliation; however, in very dry conditions the reduction in ET by defoliation might help the crop survive.

Blast fungus inoculation reduces accumulation and remobilization of pre-anthesis assimilates to rice grains

The importance of stored assimilates for grain development in cereals has been widely recognized, particularly in cereals exposed to stress during the grain filling period. This study was conducted to investigate the effect of the blast fungus Magnaporthe grisea on dry matter accumulation, remobilization and utilization in rice ( Oryza sativa L.) under field conditions. Four rice varieties with various levels of susceptibility to rice blast were grown in 2003 and 2004 under high and low disease intensity, caused by early inoculation and natural infection respectively. High disease intensity reduced plant height, dry matter accumulation, the harvest index and grain yield. Plants grown under high disease intensity translocated fewer stored assimilates to the grain than plants grown under low disease intensity. Dry matter translocation from the vegetative parts to the grain was significantly correlated with dry matter at anthesis (r=0.65, P l). High stress from early leaf blast caused by inoculation with the blast fungus affected overall plant growth and lowered the production of pre-anthesis assimilates, as well as causing severe levels of neck blast that resulted in a low translocation rate during the filling period, and therefore a lower grain yield than in naturally infected plants.

Remobilization of Dry Matter and Nitrogen in Maize as Affected by Hybrid Maturity Class

The length of the growing cycle is one of the most important traits determining hybrid adaptability to the environment. The objective of this research was to compare in a field trial the pattern of dry matter and nitrogen accumulation and remobilization of four commercial maize hybrids belonging to FAO maturity group 400, 500, 600 and 700. The duration of the periods emergence-silking and silking-physiological maturity increased with the increase of hybrid maturity class. Silking occurred 6 days later in the latest maturing hybrid than in the earliest one, and physiological maturity 21 days later. Hybrids differed for biomass production at silking and at physiological maturity. At silking, plant dry weight and leaf area increased with hybrid maturity, owing to greater leaves and stalks. The lengthening of the period emergence-silking allowed a greater accumulation of assimilates in the plant, thus increasing the source of remobilization in the following period. The increase of the length of the period silking-maturity from hybrid 400 to hybrid 700 brought to an increase of dry matter accumulation coupled to a reduction of dry matter remobilization. Increases in hybrid maturity class resulted also in an increase of post-silking N uptake and N remobilization from vegetative plant parts. Thus, the longer period silking-maturity was associated with an increased photosynthetic activity of the plant, which hampered the rate of leaf senescence and deterred the mobilization of reserve carbohydrates for grain filling. Conversely, the longer was the hybrid cycle, the greater was the quantity of both N uptake from soil and remobilized N from vegetative plant parts.

Effect of Nitrogen Rates on Dry Matter Remobilization of Three Rice Cultivars

Effect of Nitrogen Rates on Dry Matter Remobilization of Three Rice Cultivars

Evidences for the association between carbon isotope discrimination and grain yield—Ash content and stem carbohydrate in spring wheat grown in Ningxia (Northwest China)

Carbon isotope discrimination (Δ) has been repeatedly reported to positively correlate with grain yield in wheat grown under post-anthesis stress environments. Several hypotheses have been put forward to explain this association. However, there is few reported direct evidence clarified the relationship between Δ and grain yield, which is the objective of the present work. The relationships between Δ and grain yield (GY), harvest index (HI), ash content ( m a), specific stem dry weight (SSDW) and carbohydrate in stem, were studied in a collection of 20 bread wheat cultivars (landraces, released cultivars and advanced lines) in Yinchuan of the Ningxia region (Northwest of China) in three successive years (2006, 2007 and 2008). Relationships between GY, HI, stem specific dry weight, accumulation and mobilization of stem reserved carbohydrate and Δ were analyzed. The effects of year, sampling time and genotypes on measured traits were significant. Positive correlations between grain yield and Δ were noted in 2007 and 2008 when stress occurred after anthesis, but not in 2006 when soil water condition was nearly optimal. Significant and positive correlations among m a L m, grain Δ and harvest index were found. Stem water-soluble carbohydrate content (SWSCC) and specific dry weight 7 days after anthesis was positively associated with Δ. Remobilization efficiency of stem water-soluble carbohydrate and total carbohydrate (the sum of water-soluble carbohydrate and starch) was also found to be significantly and positively correlated to Δ. There were negative relationships between Δ G m, Δ S m, and SSDW at maturity. In conclusion, Δ may predict yield when irrigation does not meet crop's water requirement and wheat experiences a slight water stress after anthesis in central region of Ningxia. Δ or m a L m is related to the efficiency of carbon partitioning to the grain. Basal mature stem Δ seems to be an integrated character reflecting both early carbohydrate assimilation and dry matter remobilization to grain during grain-filling.

Improving Wheat Grain Yield under Water Stress by Stem Hydrocarbon Reserve Utilization

Current assimilation and remobilization of dry matter during grain filling in wheat subjected to different levels of water deficit during phenological growth stage. The experiment was conducted as split plot. Time of water stress and levels considered as main and sub plots, respectively. water stress treatments exposed at jointing, anthesis and seed filling stage and levels of water stress include, Full Irrigation (FI), Low Water Stress (LWS), Moderate Water Stress (MWS) and High Water Stress (HWS). Grain yield and dry matter accumulation and remobilization were negatively affected by water stress. The lowest grain yield was obtained from HWS and when water stress occurred at anthesis. Dry matter accumulation at LWS was 4.87%, at MWS was 14.86% and at HWS was 26.55% lower than FI, respectively. Spike density and the number of kernel per spike were affected similarly and decreased with water deficit increased. The decrease in the number of spikes per unit area due to LWS, MWS and HWS was 13, 23 and 30% compared to FI, respectively. As the water stress was imposed at jointing stage, the lowest number of spikes per unit area and when imposed at anthesis, the lowest number of kernel per spike was obtained. With increase in water stress intensity, the contribution of mobilized DM (DMRC) to grain yield increased. The highest DMRC value obtained from HWS with 25.37%.

Different Irrigation and Nitrogen Fertilizer Treatments on Some Agro-Physiologic Traits in Rapeseed (Brassica napus L.)

In order to investigate the effect of irrigation and nitrogen fertilizer on agronomical and physiological traits of two winter rapeseed varieties, an experiment was established in a randomized complete block design as split-plot factorial arrangement with four replications in 2005-2006 at Agricultural Research Station of Khorramabad, Iran. Irrigation as main-plot factor consisted of four levels (I60, I90, I120 and I150). Sub-plot factors included nitrogen in four levels (N0, N70, N140, and N210 kg N ha(-1)) and two varieties (Zarfam and SLM046). Thousand-seed weight (TSW) in all irrigation and nitrogen levels was lower in the 2006 than that of the 2005. Seed oil percentage (SOP) was decreased with increasing water use only in second year. As nitrogen rate increased, SOP decreased and seed oil yield (SOY) increased in the 2006 significantly (p < 0.05). With increasing water supply, SOY increased in first year. Zarfam variety had a higher TSW and SOP in both years. According to combined analysis results, seed and oil yield were not significantly affected by irrigation treatments and rapeseed varieties. Seed yield had not significant difference between 70 to 210 kg N ha(-1) treatments. Both Water Use Efficiency (WUE) and dry matter remobilization efficiency (DMRE) were increased by decreasing water supply in I90 to I150 treatments. But N0 and N210 resulted in the lowest WUE and DMRE, respectively. Considering all traits, the first year of experiment was better than second year. The irrigation x variety interaction had a significant (p < 0.01) effect on seed yield and WUE. Generally, I150N70V1 combination is recommended in the region of the study due to high performance in production of seed and oil yield.

Remobilization of Dry Matter, Nitrogen and Phosphorus in Durum Wheat as Affected by Genotype and Environment

Field studies were carried out to determine dry matter (DM), nitrogen (N) and phosphorus (P) assimilation until anthesis and DM, N and P remobilization during grain filling in wheat. Twentyfive durum wheat (Triticum durum L.) varieties were grown in Tuscany at Grosseto and at Arezzo. At Grosseto 76% of DM was assimilated during pre-anthesis while at Arezzo the amount was 81%. At Grosseto 44% and at Arezzo 35% of N was accumulated until anthesis, while 33% of P was stored until anthesis in both localities. Cultivar differences in DM and N remobilization were positively related to pre-anthesis dry matter and N content at anthesis (r &gt; 0.74). Environmental contraints on carbon, N and P availability in the plant are crucial factors in determining grain yield and N and P content in grain, affecting both accumulation and remobilization. In the low rainfall site of Grosseto, most of the grain yield originated from dry matter accumulation, while in the wetter environment of Arezzo remobilization and accumulation contributed equally to grain yield. Conversely, at Grosseto grain N content relied most on remobilization and at Arezzo remobilization and accumulation contributed equally. Finally, at Grosseto and at Arezzo accumulation of P was the main source of grain P content.

Study the Effect of Nitrogen Fertilizer Management on Dry Matter Remobilization of Three Cultivars of Rice (Oryza sativa L.)

In order to study the effect of nitrogen fertilizer management on dry matter remobilization among three rice cultivars, a field experiment was carried out at the Rice Research Institute of Iran-Deputy of Mazandaran (Amol). In 2005, a split-split experiment in the basis of randomized complete block design with 3 replications and 3 factors were used in which fertilizer rate (100, 150 and 200 kg ha(-1) from urea source), fertilizer split application (3 levels in variable ratios in transplanting, tillering and heading stages and cultivars (Tarom, Shafagh and Bahar1) were the treatments. Results showed that nitrogen fertilizer rates and split application had significant effect on dry matter remobilization amount in total shoot, stem and leaves (except flag leaf) in which among cultivars, Shafagh had the highest amount in terms of stem and total shoot dry matter remobilization. This amount was obtained at the 100 kg ha(-1) nitrogen fertilizer and the first split application treatment. The highest rate of dry matter remobilization in leaves (except flag leaf) related to Bahar1 that obtained in 200 kg ha(-1) nitrogen fertilizer level. Also, flag leaf of Bahar1 had the highest dry matter remobilization amount, although was not affected by nitrogen fertilizer rates and split application. Thus, it seams that this part has important role in current photosynthesis at post anthesis stage compared with dry matter remobilization. According to our findings, flag leaf in Tarom cultivar not only has no significant role in dry matter remobilization, but also act as a powerful sink for photosynthetic assimilates.

Post-anthesis dry matter and nitrogen dynamics in durum wheat as affected by nitrogen supply and soil water availability

Durum wheat ( Triticum durum Desf.) is commonly grown in dryland conditions, where environmental stress during grain filling can limit productivity and increase the dependency on stored assimilate. We investigated current assimilation and remobilization of dry matter and nitrogen during grain filling in N fertilized and unfertilized durum wheat subjected to different levels of water deficit during grain filling. Two durum wheat varieties, Appio and Creso, were grown in open-air containers with three rates of nitrogen fertilizer (not applied, N0; normal amount, NN; high amount, NH) and four water regimes during grain filling (fully irrigated treatment, FI; low, LWS, moderate, MWS and high water stress, HWS) across 2 years. Grain yield and dry matter and N accumulation and remobilization were positively affected by N availability and negatively by water stress during grain filling. The reduction of grain yield by severe post-anthesis water stress amounted to 27 and 37% for N0 and NN, respectively, and was associated with a decrease in kernel weight. There was also a small negative effect on the number of kernels per spike. Conversely, the duration of grain filling was not modified either by water stress or by nitrogen treatments. Severe water stress also reduced dry matter accumulation and remobilization by 36 and 14% in N0 plants and by 48 and 25% in NH plants. Similarly, N accumulation and N remobilization was reduced by 43% and by 16% in N0 plants and by 51% and by 15% in NH plants. Conversely, low and moderate water stress did not substantially modify the patterns of dry matter and nitrogen deposition in grain. Although remobilization of dry matter and N was less affected by water stress than accumulation, it was not able to counterbalance the reduction of assimilation and consequently it was not able to stabilize grain yield under drought.

Dry matter accumulation and remobilization of durum wheat as affected by soil gravel content

Soil gravel content affects many soil physical properties, i.e. bulk density, porosity, water infiltration and storage, as well as crop yield. Little is known regarding the influence of soil gravel content on grain yield of durum wheat ( Triticum durum Desf.). In this paper the accumulation of dry matter during the vegetative and reproductive periods and the contribution of pre-anthesis assimilates to grain yield have been evaluated in two durum wheat varieties grown on soils with 0, 10, 20, and 30% gravel content. The two varieties showed similar behaviour and more soil gravel decreased plant biomass both at anthesis and at maturity. Soil gravel content greatly reduced grain yield and dry weight of all plant parts both at anthesis and maturity. Post-anthesis dry matter accumulation was 16% lower in plants grown on 30% gravel soil and dry matter remobilization was 53% lower, compared to plants grown in gravel-free soil. The differences in growth rate were attributed to the restriction of the volume of soil available for root growth.

Post-anthesis accumulation and remobilization of dry matter, nitrogen and phosphorus in durum wheat as affected by soil type

The objective of the research was to quantify the changes in the accumulation of dry matter and N and P content of four durum wheat ( Triticum durum Desf.) varieties grown on two soil types (sandy-loam and clay-loam), differing for texture, nitrogen content and water holding capacity. Plants were grown in containers and were rainfed until anthesis; irrigation was performed during grain filling to avoid water stress. The difference in total vegetative weight and nitrogen and phosphorus content of plants between anthesis and maturity was used to indirectly estimate the relative contribution of pre-anthesis assimilation and remobilization to grain yield. The behaviour of the four varieties was similar as they ranked in the same order for pre-anthesis and post-anthesis dry matter accumulation and grain yield and differences in soil characteristics induced similar changes in dry matter, N and P accumulation and remobilization. Soil type greatly affected the patterns of dry matter, N and P accumulation and remobilization. Plants grown on clay-loam soil had higher dry weight and N and P content both at anthesis and at maturity and higher grain yield at maturity, compared to plants grown on sandy-loam soil and the remobilization of dry matter, N and P were 75, 140 and 55% higher. Most of the grain carbohydrates originated from photosynthates produced during grain fill, as the contribution of remobilization of dry matter to grain yield did not reach 30%, while most of the grain N and P originated from the remobilization of N and P accumulated prior to anthesis as remobilization of N accounted for 73–82% of grain N content and remobilization of P accounted for 56–63% of grain P content.

Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate

The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat ( Triticum durum Desf.) varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400 seeds m −2. Variety × seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo > Simeto > Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400 seeds m −2 primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400 seeds m −2, but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.

N application increases pre-anthesis contribution of dry matter to grain yield in wheat grown on a duplex soil

The effect of fertilizer N on the growth, post-anthesis water deficits and remobilization of dry matter in spring wheat was measured on a duplex soil at East Beverley, Western Australia. Nitrogen was applied at 15, 30 and 60 kg N ha-1 with half being applied at seeding and the remainder at 35 days after sowing (DAS), immediately before the onset of tillering. The applied N generated differences in early growth (76-117 g m-2) and dry matter at anthesis (410-693 g m-2), mainly through the effect of N on tiller number (120-171 m-2) and tiller size. It also generated differences in the water deficit, particularly after flowering. During the first 21 days after anthesis, midday flag leaf water potential fell at rates of 0.04, 0.07 and 0.13 MPa day-1 at 15, 30 and 60 kg N ha-1 respectively. Grain yield at 60 kg N ha-1 was increased by 20% relative to that of 15 kg N ha-1. The increase in grain yield resulted from an increase in the number of ears and grain number per ear. The high N treatment probably induced the increase in the number of fertile tillers (tillers with an ear), but reduced the grain size by 16% relative to the low N treatment. Contribution of preanthesis dry matter to grain yield was 193 g m-2 for the wheat receiving 60 kg N ha-1, 71 g m-2 for wheat which received 30 kg N ha-1 and only 16 g m-2 for wheat which received 15 kg N ha-1. This indicates that at high N supply, grain growth was substantially supported by pre-anthesis stored assimilates.

Reduced Irradiance Affects Dry Weight Partitioning in Easter Lily

Abstract The effects of reduced irradiance on dry weight partitioning in Easter lilies was examined by forcing vernalized bulbs of Lilium longiflorum Thumb. ‘Nellie White’ during two growing seasons. Forcing commenced in a glasshouse under standard growing conditions; immediately following flower bud initiation (FBI), plants were transferred to a range of irradiance reduction treatments (0%, 20%, 50%, or 85% reduction) in the greenhouse or to complete darkness in a growth chamber. Greenhouse irradiance reduction treatments resulted in alterations in whole-plant source-sink relationships. Total plant dry weight and overall plant quality were reduced in shaded plants. The depletion rate of mother bulb dry matter was not affected by reduced irradiance, whereas daughter bulb reserve loss was increased by irradiance reduction treatments. There was no daughter bulb reserve remobilization in plants grown in complete darkness after FBI. Flower bud and open flower dry weights were progressively reduced as irradiance was reduced. With an 85% irradiance reduction, plants forced from 17.5-cm bulbs had 63% bud abortion, whereas, with 20.0-cm bulbs, only 12% of the buds aborted. Plants grown in complete darkness after FBI became etiolated, and flowers failed to open. These results demonstrate differences in the ability of various morphological regions of the bulb to respond to reductions in greenhouse irradiance. Since the daughter bulb response to reduced irradiance was relatively slow, additional remobilization of dry matter from the daughter bulb is probably of minimal benefit during short periods of reduced irradiance in commercial greenhouses.