Rate Of Dry Matter Accumulation Research Articles

Influence of light intensity on the rate of photosynthesis and dry matter accumulation in Oriental hybrid lily ‘Siberia’ at different developmental stages

SummaryWe investigated the effects of light intensity on various photosynthetic characteristics on a whole-plant (WP) basis, focussing on three developmental stages from leafing (when young leaves unfolded) to flowering in the Oriental hybrid lily ‘Siberia’. On a WP basis, the net photosynthetic rate (Pr) was low at the leafing stage, but increased rapidly at the visible flower bud and flowering stages. However, on a leaf area (LA) basis, plants at the leafing stage exhibited a high Pr, peaking at the visible flower bud stage and diminishing slightly at the flowering stage.The rapid increase in total LA due to plant growth and development had a strong influence on Pr on a WP basis. ‘Siberia’ plants were grown under various reduced levels of natural light (0%, 40%, or 60%), achieved by shading, to evaluate the contribution of photosynthetic assimilates at various developmental stages and to compare the consistency of these results with the photosynthetic characteristics of the plants. The final dry matter (DM) content on a WP basis was determined by the light intensity applied after the visible flower bud stage, but not before. These experiments indicated that, during the growth of ‘Siberia’ lily, photosynthesis determined DM accumulation after the visible flower bud stage. Low or high light intensities before or after this stage promoted stem elongation and leaf thickening, respectively. Therefore, shading during the early developmental stages and high sunlight during the later developmental stages were beneficial for the quality of Oriental hybrid lily cut flowers.

Physiological Factors Underpinning Grain Yield Improvements of Synthetic‐Derived Wheat in Southwestern China

ABSTRACTSynthetic hexaploid wheat (SHW) is a valuable source of genetic diversity for germplasm enrichment in wheat breeding. In China, SHW‐derived material has shown significant yield increases. A 3‐yr field experiment at Guanghan and Jiangyou in the Sichuan Basin of China was conducted to characterize the potential of three SHW‐derived cultivars (SDCs) with five local elite nonsynthetic‐derived cultivars as checks (NSCs). On average, SDCs showed an 11.5% or 951 kg ha−1 yield increase compared with NSCs. This yield gain was mainly attributed to increases in both grain number m−2 (5.7%) and thousand kernel weight (5.9%). A higher rate of aboveground dry matter accumulation, especially in the early growth stages, was observed in the SDCs. The SDCs also had better partitioning to the grain, as evidenced through an increased harvest index (HI). The SDCs had a relatively compact and erect plant type with medium and upper leaves having a mean extinction coefficient at 45° (EC45°) increase of 8.4% above the NSCs at 20‐d after flowering. Correlations between grain yield components and physiological traits were analyzed. We concluded that the use of SHW has the potential to significantly increase wheat yield grown under rain‐fed environments with low photosynthetically active radiation.

Effects Of Seed Vigor On Growth And Grain Yield Of Maize

Abstract Reduction in seed vigor is a consequence of seed aging which may influence field performance of crops. Thus, a field study was conducted as RCB design with 6 replicates to evaluate the effects of seed vigor on maize (cv. Ksc 301) growth and yield. A sub-sample of maize seeds was kept as control and two other sub-samples were artificially aged for 9 and 12 days. So, three seed lots (V1, V2 and V3), with different vigor were provided and sown in the field. Mean emergence time significantly increased, but mean emergence percentage decreased as seed vigor increased. The lowest leaf area index (LAI), dry matter accumulation (DMA) and crop growth rate (CGR) were obtained for plants from the lowest vigor seed lot (V3). At the later stages of growth, the highest relative growth rate (RGR) was recorded for V1 plants, followed by V2 and V3 plants. Poor stand establishment and growth of plants from V2 and V3 seed lots led to yield loss by 23.7 % and 41.5 %, respectively. These results showed that production and cultivation of high vigor seeds are necessary to ensure satisfactory field performance of maize.

Dry-Matter Partitioning across Parts of the Wheat Internode during the Grain Filling Period as Influenced by Fertilizer and Tillage Treatments

Dry-matter transportation and redistribution is an important factor influencing grain weight during the grain filling period. This study, carried out over two consecutive winter wheat growth seasons (2010/2011 and 2011/2012), examined how dry-matter partitioning across segments of the wheat internode during grain filling period is influenced by fertilizer and tillage treatments. The contributions of current assimilates and remobilization of dry matter to final grain weight were calculated. To precisely illustrate the changes in dry matter during the grain filling period, the whole wheat stem was divided into two parts, the top three part and bottom two part. The former included three segments: the exposed part of the uppermost internode (EXUI), the enclosed part of the uppermost internode (ENUI), and the penultimate internode (PI). The latter included two segments: the lower internode (ERI) and the lowest internode (ESTI). During postanthesis, two different phases characterized by different rates of dry-matter accumulation could be distinguished. The first phase was the dry-matter accumulation; the second phase was mobilization to grains. The bottom two parts contributed more dry matter during pre-anthesis to the final grain; on the other hand, the top three parts contributed more dry matter to the final grain during postanthesis. On average, for the bottom two parts, the ERI segment had the greatest contribution of pre-anthesis dry matter to grain weight (CRAP) (3.68% in 2010/2011 and 5.31% in 2011/2012 growth seasons). For the top three parts, the EXUI segment had the greatest contribution of postanthesis photosynthetic assimilate to grain weight (CAPA) (99.71% in 2010/2011 and 99.08% in 2011/2012 growth season). The top three parts achieved maximum dry weight at 15 days after anthesis (daa), 5 days earlier than the bottom two parts. The heavy rainfall in the late grain filling period of 2011/2012 growth season inhibited postanthesis dry mobilization, and to maintain the grain filling requirements, more dry matter stored during pre-anthesis was redistributed. The present results suggest that rainfall occurring late in the grain filling period may have adverse impact on postanthesis accumulation. To avoid this phenomenon, early sowing with plastic film cover and split nitrogen application may be recommended. Fertilizing with 195 kg hm−2 (120 + 75) N plus 45000 kg hm−2 of ox manure and 120 kg hm−2 phosphate with wheat straw retention during the summer fallow period under conservation minimum tillage produced the greatest stem dry matter at anthesis.

Comparative growth, dry matter accumulation and photosynthetic rate of seven species of Eucalypt in response to phosphorus supply

Plantations of eucalypts as short-rotation tree crops are rapidly expanding in tropical and sub-tropical regions, including southern China, where the soils are acidic and available phosphorus (P) is limited. We investigated seedling growth, dry matter accumulation, and the dynamics of photosynthetic rate and chlorophyll content of seven Eucalyptus species/hybrids (E. dunnii, E. grandis, E. grandis × E. camaldulensis, E. urophylla × E. camaldulensis, E. urophylla × E. tereticornis, E. grandis × E. tereticornis, E. urophylla × E. grandis) in response to different levels of P supply (0, 6, 12 and 18 mg·kg−1 KH2PO4). The photosynthetic rate and the chlorophyll content significantly declined as the P supply declined in almost a linear fashion for all species as the P stress period extended. In the absence of P supply, height growth of seedlings of all species was significantly impaired, while root collar diameter growth and whole plant dry matter accumulation was not affected by the level of P supply in most of the species. Significant inter-species variations in growth, dry matter accumulation and photosynthetic rate in response to P supply were detected. Eucalyptus dunnii had the lowest growth performance across all levels of P supply while E. Urophylla × E. tereticornis showed superior growth performance. From a practical point of view, E. Urophylla × E. tereticornis is suggested as a candidate hybrid for planting on slightly P-deficient sites in southern China while E. dunnii, being a slow-growing species, is not suitable for short-rotation plantation. On plantation sites where severe P deficiency exists, P fertilization needs to be considered to boost rapid growth of seedlings so as to meet the management objectives of short-rotation plantation.

秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

Straw is rich in organic carbon,nitrogen( N),phosphorus( P),potassium( K),silicon( Si) and other nutrients that can improve physical,chemical and biological properties,increase crop yield,and lower fertilizer costs.Straw is mainly composed of cellulose,hemicellulose and lignin,and the C /N ratio is generally about 60—80; straw is therefore not easily decomposed by microorganisms in soil. Straw also needs to absorb a certain amount of N,for which it competes with crops,affecting seedling growth. Returning straw that contains a certain proportion of fertilizer N and P can mediate the soil C /N ratio,accelerate straw decomposition,and relieve the competition for inorganic nitrogen from microorganisms during the decomposition process. To explore the decomposition patterns of straw,we designed an experiment in Jiangxi to examine changes in dry matter production,soil properties,and biological processes in response toreturning straw. The amount of crushed straw used( 3000 kg /hm2) was determined by an examination of the effects of different amounts of returning straw on early rice. We researched the effects of returning straw containing different ratios of fertilizer on rice yield,dry matter accumulation and distribution,and soil fertility. We used a single application of straw as a control. Other treatments were SN1( 3000 kg/hm2 of crushed straw + 150 kg /hm2N),SN2( 3000 kg/hm2 of crushed straw+ 225 kg /hm2N),SP1( 3000 kg/hm2 of crushed straw + 75 kg /hm2P2O5),SP2( 3000 kg/hm2 of crushed straw + 112. 5kg / hm2P2O5),SNP1( 3000 kg/hm2 of crushed straw + 150 kg /hm2 N + 75 kg /hm2P2O5),SNP2( 3000 kg/hm2 of crushed straw + 225 kg /hm2 N + 112. 5 kg /hm2P2O5),SNPK1( 3000 kg/hm2 of crushed straw + 150 kg /hm2 N + 75 kg /hm2P2O5+ 37. 5 kg /hm2K2O),SNPK2( 3000 kg/hm2 of crushed straw + 225 kg /hm2 N + 112. 5 kg /hm2P2O5+ 56. 3 kg /hm2K2O). The results demonstrate the following:( 1) Compared with the control,the returning straw with low levels of N,P,and K significantly increase the grains per spike,1000-grain weight,seed-setting rate,filled degree of grain and overall crop yield at rates of 9. 32%,4. 28%,13. 70%,2. 74% and 26. 38%,respectively.( 2) The differences in dry matter accumulation between different growth periods are significant. Dry matter accumulation is greatest in the tilling to heading period and the filling to maturity period in all treatment groups.. The following proportion of total dry matter accumulation occurred in those two periods combined: 78. 61%,79. 22%,81. 97%,77. 95%,77. 27%,78. 13%,78. 20%,79.08%,and 78. 47% in the control group,SN1,SN2,SP1,SP2,SNP1,SNP2,SNPK1 and SNPK2,respectively. The heading to filling period is a stage of rapid accumulation of material,but because of its short duration,dry matter accumulation and the ratio of accumulation to the total amount of dry matter was lower than in the other growth periods.With growth,the ratio of stem-sheath length to total plant length continuously decreased from a range of 66. 68% —77. 00%in the booting stage to a range of 25. 97% —34. 79% in the maturity period. In addition,in the SNPK1 treatment,the ratio of leaf length to the total plant length reduced from a range of 23. 00% —33. 32% in the booting stage to a range of 7.41% —21. 03% in the maturity period. The dry weight ratio of the stem-sheath to the whole plant in the booting stage,heading stage,and at maturity was significantly higher in the treatment groups than in the control group,and was highest in the SNPK1 treatment. The dry weight ratio of the leaf to the whole plant is opposite; the ratio is highest in the control group.( 3) Compared with the control group,in the treatment groups,the pH increased by 1. 97% —4. 33%,organic carbon content increased by 3. 76% —25. 05%,total nitrogen content increased by 14. 75% —45. 90%,alkaline hydrolysis nitrogen content increased by 3. 49% —39. 90%,total phosphorus content increased by 10. 00% —55. 00%,available phosphorus content increased by 10. 45% —50. 88%,total potassium content increased by 18. 27% —100%,and available potassium content increased by 9. 39% —79. 72%; the C /N ratio decreased by 6. 02% —23. 59%. These results demonstrate that returning straw that contains fertilizer improves rice yield and dry matter accumulation rates; this translates to a higher potential yield of rice crops,and an increase in the level of soil nutrients. The combined effect of returning rice straw to fields with low levels of N,P,and K is significant. This study will provide a theoretical basis for the use of straw to increase soil fertility in southern regions of China,where rice farming is abundant.

播种期对晚季香稻香气2-乙酰-1-吡咯啉含量和产量的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 播种期对晚季香稻香气2-乙酰-1-吡咯啉含量和产量的影响 DOI: 10.5846/stxb201305211129 作者: 作者单位: 华南农业大学农学院,华南农业大学农学院,华南农业大学农学院,华南农业大学农学院,华南农业大学农学院,华南农业大学农学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31271646）；广东省自然科学基金项目（8151064201000017）；广东省农业攻关项目（2011AO20202001）；广东省农业标准化项目（4100F10003） Effects of sowing date on 2-acetyl-1-pyrroline content and yield of late season aromatic rice Author: Affiliation: College of Agriculture,South China Agricultural University,College of Agriculture,South China Agricultural University,College of Agriculture,South China Agricultural University,College of Agriculture,South China Agricultural University,College of Agriculture,South China Agricultural University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了确定华南双季稻区晚季香稻的适宜播种期，在大田条件下以桂香占和农香18为材料，研究了播种期对香稻香气2-乙酰-1-吡咯啉（2-AP）、脯氨酸代谢酶活性和产量的影响。结果表明：（1）7月20日播种的香稻的2-AP含量最高，2-AP含量较高的播期其游离脯氨酸含量、籽粒脯氨酸氧化酶活性以及脯氨酸脱氢酶活性维持在较高水平。（2）7月15日播种的桂香占和7月20日播种的农香18的产量最高，产量较高的播期具有较高的收获指数、干物质积累量和群体生长率。（3）试验条件下晚季香稻的适宜播种期为7月15日-7月20日。 Abstract:Aromatic rice, a famous rice type with high nutritional value and a distinct aroma, has been planted in South and Southeast Asian countries since ancient times. Recently, it has gained in popularity and gained a significant market share in the global rice trade resulting in higher prices and increased production in many countries. However, in China, a minimal area has been planted with aromatic rice because of its low resistance to disease, low yield and other disadvantages of the aromatic rice cultivars. As the standard of living has improved, China has begun to focus on the production of quality food, so researchers have started to pay more attention to aromatic rice and have bred some aromatic rice cultivars. However, finding ways to increase the concentration of the aroma of aromatic rice has proved challenging based on the low yield and poor quality of existing cultivars. 2-Acetyl-1-pyrroline (2-AP) is a buttered-popcorn-like aromatic compound found in both basmati and jasmine aromatic rice, and is considered a primary aromatic component of aromatic rice; this highly volatile and lipophilic compound occurs in the stems, leaves and grains of aromatic rice. L-proline is widely considered to be the nitrogen source for 2-AP and Δ-pyrroline-5-carboxylic acid (P5C) and has been proposed as one of the main precursors required for 2-AP synthesis. P5C is the common intermediate in the metabolic pathways of proline, ornithine and glutamic acid synthesis. Among these three pathways, the proline pathway is the major pathway used for the synthesis of 2-AP, in which proline to P5C is mediated by proline dehydrogenase, which is then used to synthetize 2-AP. Genetic factors play a major role in determining the aroma content of aromatic rice, and environmental factors and cultivation practices have a substantial effect on the quality of aromatic rice. The aroma of aromatic rice can be increased using low-density cultivation techniques, shallow irrigation, low levels of nitrogen, and moderate use of trace element fertilizers containing elements such as zinc, iron and lanthanum. However, unsuitable post-harvest conditions and some plant growth regulators can reduce the 2-AP content in aromatic rice considerably. Using better packaging materials, such as vacuum packing in nylon pouches, can retard volatilization of the aromatic compounds in aromatic rice. Temperature during grain filling, ripening and storage also plays an important role in the development of the aroma of aromatic rice; lower temperature, especially at night, has positive effects on aroma formation during the grain filling and ripening stages compared with higher temperature. Additionally, 2-AP content declines over time and is significantly affected by the temperature during storage. The sowing date affects proline and 2-AP content in aromatic rice as a result of variations in light and temperature conditions. Hence, a field experiment was carried out using Guixiangzhan and Nongxiang18 cultivars to determine an appropriate sowing date for late season aromatic rice in South China's double-cropping region and to study the effects of different sowing dates on aroma (2-AP), activities of proline metabolic enzymes and yield. The results show (1) Aromatic rice sown on 20 July achieved the highest 2-AP content. Treatments having higher 2-AP content also had a higher free proline content, higher proline oxidase activities in grain and higher levels of proline dehydrogenase. (2) Guixiangzhan sown on 15 July and Nongxiang18 sown on 20 July achieved the highest grain yield, and both had a high harvest index, high levels of dry matter accumulation and rapid crop growth rates. (3) The appropriate late season sowing date for aromatic rice was between 15 July and 20 July. 参考文献 相似文献 引证文献

Produção, composição química e taxa de lotação de sistemas forrageiros constituídos por coastcross-1 sobressemeada com azevém e trevos

O objetivo dessa pesquisa foi avaliar a produção de forragem, os teores de proteína bruta e fibra em detergente neutro, e taxa de lotação de três sistemas forrageiros constituídos por Coastcross-1 (Cynodon dactylon L. Pers.) + azevém (Lolium multiflorum Lam., cv. Comum); Coastcross-1 + azevém + trevo vermelho (Trifolium pratense L., cv. Estanzuela 116) e Coastcross-1 + azevém + trevo branco (Trifolium repens L., cv. Yi). O experimento foi conduzido entre 26 de abril de 2007 e 22 de abril de 2008, sendo conduzidos 11 pastejos, seis no período hibernal e cinco no estival. Para avaliação foram utilizadas vacas em lactação da raça Holandesa que receberam suplementação alimentar com concentrado à razão de 0,9% do peso corporal/dia. Avaliou-se a massa de forragem de pré e pós-pastejo, as composições botânica e morfológica e os teores de proteína bruta e fibra em detergente neutro. O delineamento experimental foi inteiramente casualizado com três tratamentos (sistemas forrageiros), duas repetições (piquetes) e avaliações independentes (ciclos de pastejos). No período hibernal foram observados resultados superiores (P<0,05) nos sistemas forrageiros consorciados com leguminosas para produção de forragem e taxa de acúmulo diário de matéria seca. Para a taxa de desaparecimento de matéria seca e taxa de lotação não foram observadas diferenças entre os sistemas forrageiros. Foi observado efeito residual do trevo vermelho sobre a Coastcross-1 + azevém, com valor superior (P<0,05) para o teor de proteína bruta e menor teor de fibra em detergente neutro.

Simple agrometeorological models for estimating Guineagrass yield in Southeast Brazil

The objective of this work was to develop and evaluate agrometeorological models to simulate the production of Guineagrass. For this purpose, we used forage yield from 54 growing periods between December 2004-January 2007 and April 2010-March 2012 in irrigated and non-irrigated pastures in São Carlos, São Paulo state, Brazil (latitude 21°57'42″ S, longitude 47°50'28″ W and altitude 860m). Initially we performed linear regressions between the agrometeorological variables and the average dry matter accumulation rate for irrigated conditions. Then we determined the effect of soil water availability on the relative forage yield considering irrigated and non-irrigated pastures, by means of segmented linear regression among water balance and relative production variables (dry matter accumulation rates with and without irrigation). The models generated were evaluated with independent data related to 21 growing periods without irrigation in the same location, from eight growing periods in 2000 and 13 growing periods between December 2004-January 2007 and April 2010-March 2012. The results obtained show the satisfactory predictive capacity of the agrometeorological models under irrigated conditions based on univariate regression (mean temperature, minimum temperature and potential evapotranspiration or degreedays) or multivariate regression. The response of irrigation on production was well correlated with the climatological water balance variables (ratio between actual and potential evapotranspiration or between actual and maximum soil water storage). The models that performed best for estimating Guineagrass yield without irrigation were based on minimum temperature corrected by relative soil water storage, determined by the ratio between the actual soil water storage and the soil water holding capacity.irrigation in the same location, in 2000, 2010 and 2011. The results obtained show the satisfactory predictive capacity of the agrometeorological models under irrigated conditions based on univariate regression (mean temperature, potential evapotranspiration or degree-days) or multivariate regression. The response of irrigation on production was well correlated with the climatological water balance variables (ratio between actual and potential evapotranspiration or between actual and maximum soil water storage). The models that performed best for estimating Guineagrass yield without irrigation were based on degree-days corrected by the water deficit factor.

Timing Nitrogen Applications for Quality Tops and Healthy Root Production in Carrot

When carrots (Daucus carota L.) are mechanically harvested, sufficient nitrogen (N) must be balanced between the roots and carrot tops; weak tops reduce yield. A 2-year study was conducted in Montcalm County, Michigan, where four replications of four N treatments (45, 90, 135, and 180 kg ha−1), were arranged in a randomized complete block design. Results showed the importance of determining pre-existing N sources, in as much as the deep taproot of carrot accessed unmeasured N in the subsoil and nitrate concentrations in irrigation water added N. The greatest yield occurred at 153–189 kg ha−1 available N while tops continued to take up N through 200–232 kg ha−1. When the last N application was made less than 35 days before harvest, the rate of N uptake exceeded dry-matter accumulation rate.

Effects of fertilization and row spacing on microenvironment within population canopy and dry matter accumulation of waxy maize

在田间试验条件下, 以糯玉米"凤糯6号"为试验材料, 研究了相同密度下, 不同施肥量(600 kg·hm^-2、750 kg·hm^-2、900 kg·hm^-2, 基肥、追肥等量)和不同行距配置(50 cm、60 cm、70 cm和80 cm)对糯玉米群体冠层内温度、光照强度、相对湿度、CO₂浓度、光温分布以及群体水分利用率、群体干物质积累和蒸煮品质的影响。结果表明: 糯玉米群体冠层内微环境除了受灌浆时期、一天中不同时间段影响, 还受行距和施肥量影响。行距70 cm时, 糯玉米群体冠层内平均温度最小; 行距为70 cm、施肥量600 kg·hm^-2时, 灌浆初期、中期和后期的光照强度都表现出最大值, 分别为236.2 μmol·m²·s^-1、275.3 μmol·m^-2·s^-1和285.4 μmol·m^-2·s^-1; 冠层相对湿度在行距70 cm、施肥量900 kg·hm^-2时最大, 在灌浆3个时期最高相对湿度分别比最低值高41.99%、33.98%和36.11%; 灌浆初期CO₂浓度最大值发生在行距80 cm、施肥量为600 kg·hm^-2时, 为362.4 mg·m^-3, 灌浆中期和后期最大值发生在行距70 cm、施肥量为600 kg·hm^-2时, 为363.4 mg·m^-3和385.7 mg·m^-3。在行距70 cm、施肥量为900 kg·hm^-2时, 灌浆3个时期水分利用效率最高, 分别比最低值高14.75%、15.18%、14.46%; 干物质积累量和生长率最大, 分别为5 066.4 kg·hm^-2和14.3 kg·hm^-2·d^-1、383.2 kg·hm^-2和15.3 kg·hm^-2·d^-1以及 13 213.4 kg·hm^-2和19.7 kg·hm^-2·d^-1。糯玉米蒸煮品质即感官品质、气味、风味、色泽、糯性、柔嫩性、皮厚薄等在行距70 cm、施肥量为900 kg·hm^-2时最佳。

Growth of Potato Plants of the ‘Asterix’ Cultivar and Accumulation of Nutrients

The objective of this research work was to quantify both the development of potato plants of the ‘Asterix’ cultivar and the accumulation of nutrients by the plants. The experiment was carried out at Perdizes, state of Minas Gerais, Brazil, in a randomized complete block design with seven treatments (sampling moments) and three replications. The spatial arrangement of the plants in the field was of 0.80 m between rows and 0.35 m between plants in the row. Plant samples were taken 30, 42, 54, 66, 78, 90, and 114 days after planting (DAP) for the determinations of plant dry matter and accumulated nutrients. The potato plant was slow to grow up to 42 DAP and the highest rate of dry matter accumulation was observed between 51 and 90 DAP. Plant cycle was of 97 days and total productivity of 44 t ha-1. Total macro nutrients accumulated by the plants up to 90 DAP were of 369.3, 184.0, 42.7, 18.0, 16.2, and 13.8 kg ha-1 of K, N, Ca, P, Mg, and S, respectively. The micronutrients Fe, Mn, Zn, B, and Cu were found to have reached values of 1,225, 525, 439, 164, and 96 g ha-1, respectively.

Photosynthetically relevant foliar traits correlating better on a mass vs an area basis: of ecophysiological relevance or just a case of mathematical imperatives and statistical quicksand?

Plant biologists have long had a choice of the dimensions in which to express their studied traits and/or processes. For example, a plant physiologist working at the leaf level might typically measure and report photosynthetic rates as a flux per unit leaf area (e.g. μmol CO₂ m⁻² s⁻¹) whereas a biochemist might typically express the same process per unit chlorophyll. An agronomist or forester would usually be more interested in dry matter accumulation rate per unit ground area (Mg ha⁻¹ yr⁻¹) or sometimes even as a relative growth rate (g DW g⁻¹ DW d⁻¹). Although expressing leaf-level photosynthesis on an area basis seems intuitive and was for decades the standard practice, starting with Field & Mooney (1986) and then Reich & Walters (1994), there has been an increasing tendency to express the photosynthetic characteristics of leaves on a dry-weight basis (typically nmol CO₂ g⁻¹ s⁻¹). This trend has been due, at least in part, to stronger correlations for mass-based photosynthetic rates with foliar properties thought to be important in their modulation (Reich et al., 1998). Weaker associations between foliar properties when expressed on an area-basis have also provided one rationale for the inclusion of mass-based measures of photosynthesis, nitrogen and phosphorus into a so-called 'leaf economics spectrum' (Wright et al., 2004) and with mass-based measures of photosynthetic carbon exchange subsequently underlying further analyses (Shipley et al., 2006). Some modelling studies investigating the relative importance of nitrogen vs phosphorus as modulators of leaf photosynthetic capacity have likewise been parameterized on a mass rather than an area-basis because of the apparently superior model fit of the former (Domingues et al., 2010).

Effect of Dry Matter Accumulation Characteristics on Yield of Winter Wheat Analyzed by Dynamic Simulation Model

To disclose the quantitative relationship between yield and dry matter accumulation in winter wheat, we designed three field experiments to obtain wheat populations with varying sowing date, basic seedlings, amounts of basic fertilizers, date and quantity of topdressed nitrogen fertilizer, irrigation amounts before wintering, amounts and date of irrigation after regreening of wheat in 2009–2010 and 2010–2011 growing seasons. Dry matter accumulation before wintering was represented by dry weight per plant and total stem and tiller numbers at prewintering stage, while dry matter after wintering was described by the Logistic curve characteristics based on relative accumulated temperature (R GDDi ). The grain yield and yield components of winter wheat were closely related to characteristic parameters such as maximum rate of dry matter accumulation and two inflection points in the curve for dry matter accumulation rate. Paired-sample t-test was used to validate the models established, and no significant difference was observed between the simulated and observed values. The results indicate that the Logistic model is able to describe the process of dry matter accumulation and the formation of grain yield and its components in winter wheat. The models established can be used in analysis of population regulation in winter wheat.

Canopy Physiology and Characteristics of Yield Components during Reproductive Stage in Soybean Hybrids

Utilization of soybean hybrid is an effective way to increase soybean yield. We used two soybean hybrids(HybSoy-1and HybSoy-2) and two conventional varieties(CV) with the same maturity(Jiyu 72 and Jilin 30) as materials to explore physiological characters of canopy, traits of yield and yield components, and the physiological mechanism of increasing yield in soybean hybrid at reproductive stage. The result showed that, from 2010 to 2011, compared with CV, the yields of soybean hybrids were increased by 13.9% and 16.7%. Leaf chlorophyll contents at late growth stages, photosynthetic rates at R2(full bloom)–R7(beginning maturity) and leaf area indices(LAI) at R2–R4(full pod) were all significantly higher than those of CV; the maximum LAI of HybSoy-1 and HybSoy-2 in 2010 were 8.09 and 8.30, far more than those of CV, and LAI at late growth stages were not decreased sharply. Biomasses of all varieties reached a peak at R6 stage, while those of soybean hybrids at R2–R7 were higher than those of conventional varieties with significant difference between them at P0.05 and P0.01; the means and maximum accumulation rates of biomasses were 0.06 g d–1and 0.20 g d–1more than those of conventional varieties, respectively; and the days of speeding up or slowing down dry matter accumulation rate were ahead of 3.09 days and 5.85 days than those of CV, respectively, so premature advantage of dry matter accumulation was also obvious. As for yield components, there was no significant difference between hybrids and conventional soybean varieties on 100-seed weight, grain weight and pod weight of main stem, but grain weight and pod weight of branch in soybean hybrids were significantly higher than those in conventional varieties.There was no significant difference in the ratio of grain weight to biomass and the ratio of grain weight to stem weight between soybean hybrids and conventional soybean varieties. All results showed that the yields of soybean hybrids mainly depend on the strong canopy, high speed of dry matter accumulation, and higher biomass.

Phenological Response of Rice Plants to Different Micronutrients Application under Water Saving Paddy Fields on Calcareous Soil

Due to a reduction of world water resources, rice cultivation has shifted from flooded to aerobic condition. This shift may alter soil physico-chemical conditions and cause reduced availability and uptake of nutrients, especially boron and zinc in calcareous soils, and may ultimately reduce yield. Thus a field experiment in a calcareous soil was conducted in which basal application of boron & zinc alone, or in combination, was undertaken in rice grown aerobically (T1), flooded for the entire growth period (T2) or flooded for two weeks after transplanting, given supplemental irrigation up to panicle initiation and then flooded from panicle initiation to physiological maturity (T3). The study showed that rice crop was significantly reduced growth in term of Leaf Area Index (LAI), Leaf Area Duration (LAD), Crop Growth Rate (CGR), Total Dry Matter accumulation (TDM) and Net Assimilation Rate (NAR) when it was grown in aerobic condition. However, the crop was not affected significantly different from normal flooded rice (T2) when it was grown in modified rice culture (T3). Application of zinc alone or in combination with boron enhanced chlorophyll contents in T2similar to T3 while the crop grown in aerobic condition (T1) had significantly lower chlorophyll content

Characteristics of Dry Matter Accumulation and Translocation in Rice Cultivars with High Yield and High Nitrogen Use Efficiency

The difference of dry matter production and translocation characteristics in low-yielding and low N-efficiency, high-yielding and medium N-efficiency, high-yielding and high N-efficiency rice cultivars was investigated using six representative japonica varieties under their optimum N supply levels, respectively. The results indicated that: with the increase of rice productivity, the total dry matter production amount significantly increased by 20.29% on average, and the dry matter accumulation amount and population growth rate increased on average by 15.05%, 27.04%, 24.75% and 15.05%, 28.38%, 23.00%, during the period before N-n (critical stage of productive tillering), from jointing to heading, and from heading to maturing, respectively, and decreased during the period from N-n to the jointing. Among the high-yielding varieties, with the nitrogen use efficiency increased, the tiller number per unit area at each growth stage showed a downward trend, and significantly reduced on average by 5.76%, 11.61%, 7.01%, and 5.70% at N-n, jointing, heading and maturing, respectively, but ratio of productive tillers to total tillers significantly increased. At each growth stage, the dry matter accumulation amount showed a declined tendency, and reduced on average by 12.18%, 10.54%, 8.29%, and 5.01% at N-n, jointing, heading and maturity, respectively, but harvest indexsignificantly increased. During the period from heading to maturing, dry matter accumulation rate increased on average by 5.40%, the population growth rate increased on average by 5.19%. The results above showed that proper control for population growth before heading, maintaining a high growth rate after heading and a higher harvest index were the important dry matter accumulation characteristics of the cultivars with high-yielding and high nitrogen use efficiency.

Análise de crescimento e produtividade de cultivares de arroz de terras altas dos tipos tradicional, intermediário e moderno

A utilização da técnica de análise de crescimento permite caracterizar e entender o comportamento diferenciado de cultivares de arroz de terras altas. Este trabalho objetivou caracterizar, por meio da análise de crescimento, os componentes fisiológicos e o desempenho agronômico, bem como as diferenças existentes entre cultivares de arroz de terras altas do tipo tradicional, intermediário e moderno. O experimento foi conduzido em condições de terras altas, favorecidas pelo uso de irrigação suplementar. O delineamento experimental utilizado foi em blocos ao acaso, com três tratamentos constituídos por cultivares do tipo tradicional (Caiapó), moderno (Maravilha) e intermediário (BRS Primavera) e oito repetições. Foram estimados o índice de área foliar (IAF), taxa de crescimento da cultura (TCC), taxa de crescimento relativo (TCR), taxa assimilatória líquida ou aparente (TAL) e área foliar específica (AFE), além da produtividade de grãos e componentes de produção. As cultivares dos grupos intermediário e tradicional apresentaram os maiores acúmulos de matéria seca total e as dos grupos tradicional e moderno os maiores IAFs. A cultivar do grupo intermediário apresentou os maiores índices de TCC, TCR, TAL e AFE, bem como a maior produtividade de grãos, em decorrência dos maiores valores de fertilidade das espiguetas e massa de 1.000 grãos.

Production parameters and forage loss of oat and rye grass pastures managed with beef heifers fed diets with energy supplementation

Production parameters of intercropped pastures of oat and rye grass managed with beef heifers supplemented with brown rice meal and/or protected fat were evaluated. Twenty-eight Charolais × Nellore crossbred heifers at initial average age of 18 months and initial average live weight of 274.9 kg were utilized in the experiment. Animals were kept on oat + rye grass pastures and distributed in the following treatments: no-supplementation (NS): heifers kept only in pastures; Megalac (MEG): supplementation with protected fat; brown rice meal (BRM): supplementation with BRM; BRM + MEG: supplementation with BRM plus protected fat. The greater participation of oat leaf was from July 5th to August 10th, 2009 and of rye grass, from August 30th to September 26th, 2009. The crude protein content increased until the 55th day (225.1 g/kg). Pasture total digestible nutrients presented a cubic behavior, with an average of 722.0 g/kg. The highest supply of leaf blades, 5.17 kg of dry matter/100 kg of live weight, was found in the second period. Pasture intake increased throughout the periods. Forage mass and support capacity of the animal did not differ between treatments, presenting means of 1245.02 kg of dry matter/ha and 882 kg of live weight/ha, respectively. Stoking rate, forage loss and pasture intake were not affected by the treatments. Supplementation of beef heifers with rice meal and/or protected fat did not change production parameters of oat + rye grass pastures or pasture intake. Increase in daily accumulation rate of dry matter and supporting capacity of the animals increases forage losses.

Acúmulo de nitrogênio, fósforo e potássio pelo algodoeiro sob irrigação cultivado em sistemas convencional e adensado

O adensamento da cultura do algodão aumenta a competição entre plantas por recursos, como luz, nutrientes e água; logo, o período de florescimento é reduzido e, consequentemente, a marcha de acúmulo de matéria seca é alterada. O objetivo deste trabalho foi determinar a marcha de absorção de N, P e K pelo algodoeiro, identificando a época de maior absorção e a quantidade absorvida e exportada em espaçamentos adensado (48 cm - 20,58 plantas m-2), intermediário (75 cm - 13,30 plantas m-2) e convencional (96 cm - 10,39 plantas m-2). Foram amostradas três plantas úteis por parcela aos 46, 69, 99, 139, 148 e 166 dias após a emergência (DAE), em que foram determinados o acúmulo de matéria seca, N, P e K. O acúmulo de matéria seca nas plantas cultivadas no espaçamento de 48 cm foi maior no início do desenvolvimento, igualando-se às demais ao final do ciclo, o que resultou em maior acúmulo de N entre os 69 e 99 DAE, no menor espaçamento. O adensamento antecipa o pico de absorção de nutrientes, sugerindo a antecipação das adubações de cobertura com N e K no algodoeiro cultivado nesse sistema. Para condições de fertilidade média/alta, a dose de nutrientes a ser aplicada não precisaria ser alterada em função do aumento da densidade de plantas, pois não há variação nas quantidades de N, P e K exportados por kg de algodão produzido, em fibra ou em caroço.