Understanding Dry Matter and Nitrogen Accumulation with Time-Course for High-Yielding Wheat Production in China

Understanding the time-course of dry matter (DM) and nitrogen (N) accumulation in terms of yield–trait relationships is essential to simultaneously increase grain yield and synchronize N demand and N supply. We collected 413 data points from 11 field experiments to address patterns of DM and N accumulation with time in relation to grain yield and management of winter wheat in China. Detailed growth analysis was conducted at the Zadok growth stages (GS) 25 (regreening), GS30 (stem elongation), GS60 (anthesis), and GS100 (maturity) in all experiments, including DM and N accumulation. Grain yield averaged 7.3 Mg ha⁻¹, ranging from 2.1 to 11.2 Mg ha⁻¹. The percent N accumulation was consistent prior to DM accumulation, while both DM and N accumulation increased continuously with growing time. Both the highest and fastest DM and N accumulations were observed from stem elongation to the anthesis stage. Significant correlations between grain yield and DM and N accumulation were found at each of the four growth stages, although no positive relationship was observed between grain yield and harvest index or N harvest index. The yield increase from 7–9 Mg ha⁻¹ to >9 Mg ha⁻¹ was mainly attributed to increased DM and N accumulation from stem elongation to anthesis. Although applying more N fertilizer increased N accumulation during this stage, DM accumulation was not improved, indicating that N fertilizer management and related agronomic management should be intensified synchronously across the wheat growing season to simultaneously achieve high yields and match N demand and N supply.     

Dry Matter Partitioning between Plant Organs in Wheat Cultivars Differing in Productivity and Drought Resistance

In microplot field experiments conducted over the course of 12 years, the accumulation of dry matter was recorded in the leaves, stems, and ears of the primary shoots of plants of four cultivars of spring wheat (Triticum aestivumL.) differing in productivity and drought resistance. The contribution of organs to the accumulation of dry matter by the shoot from emergence to anthesis was calculated, and relative changes in the weight of the ear after anthesis were assessed. In all the cultivars, the contribution of the leaves was the same; however, the share of the ear was greater in short-stem cultivars of the intensive type in which the leaves were more active during the time of grain filling. Furthermore, this load increased, and the relative increment in the ear weight after flowering decreased in the years of drought, because the contribution of the leaves did not depend on water supply during the growing season. During these years, the contribution of the ear increased in the plants of all the cultivars. The authors conclude that, in arid regions, in addition to drought resistance, the cultivar should display such a ratio between the ear weight and the weight of leaves that would still ensure satisfactory grain filling     

Carbohydrate, Nitrogen and Dry Matter Accumulation and Partitioning of Maize Hybrids Under Drought Stress

Maize (Zea mays L.) productivity under drought stress dependsto some extent upon a hybrid's capacity to produce and translocateassimilate to its developing kernels during the stress periodand/or after the stress is relieved. The objective of this studywas to evaluate differences in carbon and nitrogen accumulationand partitioning under drought stress among maize hybrids thatdiffer in yield potential and/or physiological metabolism duringreproductive development. The hybrids B73 x LH38, FS854, B73xMol7and US13 were subjected to drought stress from the 7th leafstage until pollination was completed, at which time the soilof the stressed plots was replenished with water. For d. wtand chemical constituent determinations, plants of each hybridwere harvested from the irrigated and drought stressed plotsat silking, mid-grain fill, and physiological maturity. Averagedover hybrids, vegetative biomass at silking was reduced 25%as a result of the drought stress treatment, with B73 x LH38and FS854 accumulating more total biomass during the later portionof grain fill than the other two hybrids under both soil moisturetreatments. At silking, the total non-structural carbohydratecontent of the hybrids' vegetative tissue was not changed asa result of drought stress, whereas their reduced nitrogen (N)contents were decreased by an average of 33%. B73 x LH38 andFS854 had greater grain carbohydrate and reduced N contentsunder irrigation and smaller decreases in those variables asa result of soil moisture deficit than did the other two hybrids.These results indicate that the greater drought tolerance ofB73 x LH38 and FS854 to stress imposed during vegetative andearly reproductive development resulted from their more activeN uptake and assimilation and sugar production during the laterportion of grain fill and from their more efficient partitioningof assimilate to the developing kernels. Zea mays L., maize, drought stress, nitrogen, carbohydrates, hybrids, partitioning     

Effect of Seawater on Photosynthesis and Dry Matter Accumulation in Developing Rice Grains

To understand the physiology of rice under seawater salinity, potted rice plants were irrigated with different concentrations of Japan seawater (electrical conductivity 0.9, 5.7, 11.5, or 21.5 mS cm^-1) from 10 d after transplanting (DAT) to 35 DAT, and from 75 to 100 DAT. Seawater salinity decreased the net photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, transpiration rate, leaf water and osmotic potentials, and relative water content, and increased leaf temperature. The contents of chlorophylls, carotenoids, and total sugars significantly decreased in the leaves but content of non-reducing sugars decreased only slightly. With increasing salinity the Na⁺ concentration increased, while Ca²⁺, Mn²⁺, and K⁺ concentrations decreased. Salinity decreased the contents of sugars and proteins, dry mass, and rate of dry mater accumulation in developing grains.     

Characterization of Spring Wheat Genotypes Differing in Drought-Induced Abscisic Acid Accumulation: II. LEAF WATER RELATIONS

Aspects of the water relations of spring wheat (Triticum aestivumL.) are described for cultivars Highbury (low ABA) and TW269/9(high ABA), and low and high ABA accumulating F⁶selections derivedfrom a cross between them. In a pot experiment, pressure-volume (P-V) curves were constructedfor main stem leaf four (MSL4) of well-watered plants of Highburyand TW269/9. Estimates of solute potential (²) from these curveswere similar for the two cultivars, but varied with the timeof sampling and the time allowed for hydration in dim light. In a field experiment with four low and four high ABA F⁶lines,P-V curves for flag leaves from both droughted and irrigatedplants gave at both zero turgor (^p) and zero water potential(¹) which differed with degree of stress, sampling time andgenotype. ¹was strongly dependent on the initial_L of the leafand was reduced on average by c. 0.4 MPa per MPa decline ininitial L.5, was lower (more negative) by c. 0.1-MPa in theafternoon than in the morning. Overall, was also 0.1 MPa lowerin low ABA lines than in high ABA lines. In another field experiment, flag leaves of five low and fivehigh ABA F⁶lines were sampled over a 4 week period from droughtedplots and _L and 5, measured (the latter by osmometry with expressedsap). For these leaves 5, at zero p or zero _L was consistentlylower by 0.3–0.5 MPa than estimates of 5, from the P-Vcurves with flag leaves. However, data for the low ABA lineswere again lower (by c. 0.1 MPa) than those for high ABA lines. The consequences of these differences in 1 are discussed inrelation to the stimulation of ABA accumulation in low and highABA selections. Key words: Water potential, Solute potential, P-V curves, Wheat (Triticum aestivum), Drought stress     

Effect of Nitrogen on Growth, Yield and Photorespiratory Activity in Spring Wheat

Spring wheat plants growing in pots in controlled environmentrooms were given extra nitrogen after flag leaf emergence. Theeffect of nitrogen on growth, yield, the activity of ribulose1,5–bisphosphate carboxy–lase/oxygenase and thedistribution of¹⁴C in photorespiratory intermediates and indifferent parts of the plants was determined. Extra nitrogenincreased the movement of ¹⁴C to the ear and increased grainyield by 29 per cent, mainly because of an increase in grainnumber. Though extra nitrogen delayed senescence of the leaves,the growth of the ear in the later stages was not increasedin proportion to the extra green area. The relative inefficiencyof leaf area with extra nitrogen, which has also been foundin the field, was not due to a reduction in photosynthesis perunit leaf area. Nor was there evidence of an increase in photorespirationas reflected by a greater flow of carbon into the photorcspiratorymetabolites glycine and serine, or an increase in the activityof ribulose 1,5–bisphosphate oxygenase relative to thecarboxylase. We suggest that there may be an increase in theloss of carbon in dark respiration. Triticum aesttvum, nitrogen, growth, yield, photorespiration     

Effect of Nitrogen and Water Stress on Photosynthesis and Nitrogen Content in Wheat

The relationships between photosynthesis, leaf nitrogen content and water stress were studied in ten genotypes of wheat differing in the presence of dwarfing genes. Net photosynthetic rate (P_N) was mostly higher at ear emergence stage than at anthesis stage. P_N decreased with water stress (leaf water potential from –2.0 to –2.5 MPa), and with reduced leaf N content in all genotypes studied. Among the various genotypes, single dwarf and wild types showed higher P_N rate and maintained higher leaf N content under different N doses and water supply as compared to the other types studied.     

Comparison of Whole System of Carbon and Nitrogen Accumulation Between Two Maize Hybrids Differing in Leaf Senescence

A field experiment was conducted to investigate the carbon (C) and nitrogen (N) balance in relation to grain formation and leaf senescence in two different senescent types of maize (Zea mays L.), one stay-green (cv. P3845) and one earlier senescent (cv. Hokkou 55). In comparison with Hokkou 55, P3845 had a higher N concentration (N_c) in the leaves and a higher specific N absorption rate by roots (SAR_N), which indicated that a large amount of N was supplied to the leaves from the roots during maturation. This resulted in a higher photosynthetic rate, which supports saccharide distribution to roots. Thus, stay-green plants maintained a more balanced C and N metabolism between shoots and roots. Moreover, the coefficients of the relationship between the relative growth rate (RGR) and N_c, and between the photon-saturated photo-synthetic rate (P _sat) and N_c were lower in P3845. The P _sat per unit N_c in leaves was lower in the stay-green cultivars, which indicated that high yield was attained by longer green area duration and not by a high P _sat per unit N_c in the leaf. Consequently, a high P_sat caused a high leaf senescence rate because C and N compounds will translocate actively from the leaves.     

Water Deficit as a Driver of the Mutualistic Relationship between the Fungus Trichoderma harzianum and Two Wheat Genotypes

The aim of this study was to assess the occurrence of mutualistic interactions between the fungus Trichoderma harzianum and two wheat genotypes, Triticum aestivum cv. Talhuén and T. turgidum subsp. durum cv. Alifén, and the extent to which water deficit affected these interactions. Two wheat genotypes were cultivated in the presence or absence of T. harzianum and in the presence or absence of water deficit. T. harzianum was in turn cultivated in the presence or absence of wheat plants and in the presence or absence of water deficit. To evaluate the plant-fungus interactions, the root volume, dry biomass, and fecundity of wheat were determined, as was the population growth rate of the fungus. Trichoderma harzianum exerted a positive effect only on plants subjected to water deficit. The population growth rate of T. harzianum was negative in the absence of wheat plants and reached its highest level in the presence of plants under conditions of water deficit. These results confirm the occurrence of a mutualistic interaction between wheat and T. harzianum and show that it is asymmetric and context dependent.     

黄芩干物质累积和氮磷钾吸收、分配规律研究

为了探讨黄芩干物质累积和氮、磷、钾吸收与分配的特点及两者间的相互关系,通过田间试验和采样分析,研究了黄芩不同生育期植株的干物质和氮、磷、钾累积量.结果表明,黄芩干物质的累积量随生育进程不断地增加,出苗后52～85 d干物质累积量占总累积量的61.62％.在整个生育期,黄芩对K2O的吸收累积量最大,N次之,P2O5最小,N、P2O5、K2O吸收比例约为2.8∶1.0∶2.9,并且黄芩地上部氮磷钾的累积量大于根部,不同生育期,根部N、P2O5、K2O的累积比例呈现增加—降低—增加的趋势.黄芩对氮磷钾的积累量与干物质积累量呈极显著正相关关系.在供试的土壤和施肥条件下,每生产100 kg的黄芩根需要从土壤和肥料中吸收6.34 kg的N,2.60 kg的P2O5,7.02 kg的K2O.     

Effect of Drought on Metabolism and Partitioning of Carbon in Two Wheat Varieties Differing in Drought-tolerance

A model was constructed to describe the partitioning of carbonon the third and seventh day from anthesis for well-wateredand droughted plants of two wheat varieties (Triticum aestivumL. cv. Warigal and Condor). The glasshouse-grown plants weredetillered so that a simplified model could be derived for themain stem. The 9-d drought treatment, imposed just after anthesisduring the period of cell division in the grains, reduced grainyield by 18 per cent in Warigal and 30 per cent in Condor. Netcarbon fixation was up to 60 per cent higher in Warigal thanCondor towards the end of the drought period and this correlatedwith better osmotic adjustment in the flag leaf. Carbon partitioningbetween plant organs responded to water deficit more rapidlythan net carbon fixation. On day 3, carbon allocation to theroots of droughted plants was maintained in Condor and increasedby 14 per cent in Warigal, whereas carbon allocation to theear decreased in both varieties. However the roots did not competewell with the ear when the water deficit became more severe.Warigal accumulated 3 times more stem reserves than Condor underdrought. In the roots, the pattern of carbon allocation betweenrespiration and carbon accumulation changed soon after impositionof drought. Although total root respiration decreased underdrought it became more energy efficient, particularly for Warigal,as less respiration took place via the alternative pathway.On day 3, the larger carbon allocation to the roots and thelower root respiration accounted for the 4-times larger sugaraccumulation in droughted roots of Warigal compared with thoseof Condor. Osmotic adjustment in mature leaves and roots maybe of importance for the maintenance of vital processes andfor recovery after drought. Triticum aestivum L., wheat, drought, carbon, partitioning     

Fruit Set, Abscission and Dry Matter Accumulation on Girdled Branches of Macadamia

The patterns of fruit growth, abscission and dry matter accumulationwere determined for ungirdled macadamia branches and comparedwith the patterns on girdled branches. The relationships betweenfruit set, fruit drop, and the number of available leaves werealso assessed. Approximately 50 leaves were required to supportdevelopment of each fruit on girdled branches, so that finalfruit numbers on girdled branches were higher or lower thanon ungirdled controls, depending on leaf number. High leaf numbersdid not cause any increase in fruit size on girdled branches,but low leaf numbers resulted in fruit volumes up to 23% lowerthan the controls. The number of fruits set on ungirdled brancheswas independent of the number of leaves on the branch. Defoliationof ungirdled branches had no effect on the number of fruitsset, with fruit set on these branches apparently being supportedalmost entirely from carbohydrates obtained elsewhere in thetree. Three phases of fruit drop were observed, with maximaat 2, 6-7, and 10 weeks post-anthesis, separated by phases ofrelatively low fruit drop at 4 and 8 weeks post-anthesis. Themaximum dry weight increase of the crop occurred between 10and 20 weeks post-anthesis, when there was very little fruitdrop. Therefore, although limited availability of assimilatesmay influence fruit retention in macadamia, there is no simplerelationship between structural carbon demand and fruit drop.Copyright1994, 1999 Academic Press Macadamia integrifolia Maiden and Betche, Macadamia tetraphylla L. A. S. Johnson, Proteaceae, macadamia, fruit set, fruit drop, girdling     

水稻光合生产与干物质累积的动态模拟

在综合已有研究成果的基础上,兼顾模型的机理性与实用性的平衡,构建了水稻光合生产与干物质累积的模拟模型．模型采用高斯积分法有效地计算冠层每日的总光合量,并考虑了冠层消光系数随生理发育时间（PDT)的动态变化,模型较充分地量化了生理年龄、温度、叶片含氮量及水分亏缺因子等对光合作用的影响及维持呼吸系数与PDT的动态变化关系、利用独立的试验资料对模型核实的结果显示,模型可以较好地预测不同生长条件下的生物量累积动态,具有较强的机理性与实用性．     

水分亏缺对冬小麦净光合速率影响程度研究

水分亏缺对冬小麦净光合速率影响程度研究王慧（西北大学城市与资源学系,西安７１００６９）ＥｆｆｅｃｔｏｆＷａｔｅｒＤｅｆｉｃｉｔｏｎＮｅｔＰｈｏｔｏｓｙｎｔｈｅｓｉｓＲａｔｅｏｆＷｉｎｔｅｒＷｈｅａｔ．ＷａｎｇＨｕｉ（ＤｅｐａｔｍｅｎｔｏｆＵｒｂａｎ...     

Effect of Phosphorus Deficiency and Water Deficit on Phosphatase Activities from Wheat Leaves

Wheat was sown in a phosphorus (P) deficient soil. Plants atlow levels of applied P had lower growth rates and lower concentrationsof phosphate in the shoots than plants grown with ‘highP’. Activities of both insoluble and soluble phosphataseincreased with P deficiency in the mature leaves. Soluble phosphataseactivities increased 2.5–3.0 fold as the concentrationof phosphate in the leaves fell from 0.4% to 0.1% dry weightThis increase was not a consequence of reduced growth, as severenitrogen deficiency had no effect on phosphatase activity. Soluble phosphatase activities were higher in young than inmature leaves, and also increased 3–4 fold with severewater deficit. However these increases in activity were notaccompanied by low concentrations of phosphate. Moreover, solublephosphatase activities in mature leaves of plants grown underconditions of water deficit rapidly decreased after rewatering.In contrast, the high soluble phosphatase activities in matureleaves of P deficient wheat persisted for up to 12 d after theresupply of P to adequate levels.     

Effect of Root and Shoot Meristem Temperature on Shoot to Root Dry Matter Partitioning and the Internal Concentrations of Nitrogen and Carbohydrates in Maize and Wheat

Maize (Zea mays L.) and spring wheat (Triticum aestivum L.)were grown in nutrient solution at uniformly high air temperature(20 °C), but different root zone temperatures (RZT 20, 16,12 °C). To manipulate the ratio of shoot activity to rootactivity, the plants were grown with their shoot base includingthe apical meristem either above (i.e. at 20 °C) or withinthe nutrient solution (i.e. at 20, 16 or 12 °C). In wheat, the ratio of shoot:root dry matter partitioning decreasedat low RZT, whereas the opposite was true for maize. In bothspecies, dry matter partitioning to the shoot was one-sidedlyincreased when the shoot base temperature, and thus shoot activity,were increased at low RZT. The concentrations of non-structuralcarbohydrates (NSC) in the shoots and roots were higher at lowin comparison to high RZT in both species, irrespective of theshoot base temperature. The concentrations of nitrogen (N) inthe shoot and root fresh matter also increased at low RZT withthe exception of maize grown at 12 °C RZT and 20 °Cshoot base temperature. The ratio of NSC:N was increased inboth species at low RZT. However this ratio was negatively correlatedwith the ratio of shoot:root dry matter partitioning in wheat,but positively correlated in maize. It is suggested that dry matter partitioning between shoot androots at low RZT is not causally related to the internal nitrogenor carbohydrate status of the plants. Furthermore, balancedactivity between shoot and roots is maintained by adaptationsin specific shoot and root activity, rather than by an alteredratio of biomass allocation between shoot and roots.Copyright1994, 1999 Academic Press Wheat, Triticum aestivum, maize, Zea mays, root temperature, shoot meristem temperature, biomass allocation, shoot:root ratio, carbohydrate status, nitrogen status, functional equilibrium     

Water Stress Induced Proline Accumulation in Contrasting Wheat Genotypes as Affected by Calcium and Abscisic Acid

Proline accumulation and mobilization in roots of 7-d-old seedlings of wheat genotypes varying in sensitivity towards water stress were compared. Water stress was induced by polyethylene glycol (PEG-6000; osmotic potential −1.5 MPa) in the presence of 0.1 mM abscisic acid (ABA), 1 mM calcium chloride, 0.5 mM verapamil (Ca²⁺ channel blocker), 0.5 mM fluridone (inhibitor of ABA biosynthesis). While both the genotypes did not differ in total proline accumulation, rate of proline accumulation and utilization was higher in tolerant genotype C 306 as compared to susceptible genotype HD 2380. The treatment with ABA and CaCl₂ caused further increase in proline accumulation during stress and reduced its mobilization during recovery. The membrane stability and elongation rate of roots was observed to be higher at ABA and calcium treatment in both the genotypes under stress. As was evident from inhibitor studies, the tolerant genotype was more responsive to ABA and the susceptible one to calcium. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Effects of Elevated Atmospheric Carbon Dioxide and Water Stress on Ligth Interception, Dry Matter Production and Yield in Stands of Groundnut (Arachis hypogaea L.

Stands of groundnut (Arachis hypogaea L.), a C₃ legume, weregrown in controlled-environment glasshouses at 28 °C (±5°C)under two levels of atmospheric CO₂ (350 ppmv or 700 ppmv) andtwo levels of soil moisture (irrigated weekly or no water from35 d after sowing). Elevated CO₂ increased the maximum rate of net photosynthesisby up to 40%, with an increase in conversion coefficient forintercepted radiation of 30% (from 1–66 to 2–16g MJ^–1) in well-irrigated conditions, and 94% (from 0–64to 1·24 g MJ^–1) on a drying soil profile. In plantswell supplied with water, elevated CO₂ increased dry matteraccumulation by 16% (from 13·79 to 16·03 t ^–1) and pod yield by 25% (from 2·7 to 3·4t ha^–1).However, the harvest index (total poddry weight/above-grounddry weight) was unaffected by CO₂ treatment. The beneficial effects of elevated CO₂ were enhanced under severewater stress, dry matter production increased by 112% (from4·13 to 8·87 t ha^–1) and a pod yield of1·34t ha^–1 was obtained in elevated CO₂, whereascomparable plotsat 350 ppmv CO₂ only yielded 0·22 t ha^-1.There was a corresponding decrease in harvest index from 0·15to 0·05. Following the withholding of irrigation, plants growing on astored soil water profile in elevated CO₂ could maintain significantlyless negative leaf water potentials (P<0·01) for theremainder of the season than comparable plants grown in ambientCO₂, allowing prolonged plant activity during drought. In plants which were well supplied with water, allocation ofdry matter between leaves, stems, roots, and pods was similarin both CO₂ treatments. On a drying soil profile, allocationin plants grown in 350 ppmv CO₂ changed in favour of root developmentfar earlier in the season than plants grown at 700 ppmv CO₂,indicating that severe waterstress was reached earlier at 350ppmv CO₂. The primary effects of elevated CO₂ on growth and yield of groundnutstands weremediated by an increase in the conversion coefficientfor intercepted radiation and the prolonged maintenance of higherleaf water potentials during increasing drought stress. Key words: Arachis hypogaea, elevated CO₂, water stress, dry matter production