The Translocation of 14C-Sucrose and 14C-Benzyl Adenine in Winter Wheat (Tritkum aestivum L.) in the Period of Kernel Formation

The transport and distribution of ^14C-sucrose and ^14C-BA were studied in internode segments with ear of two winter wheat cultivars with a different mass of kernels in the period of kernel formation. While ^MC-sucrose was transported and accumulated intensively in the developing ear, ^14C-BA was transported much less and only a small part of it was found in the ear. With the ear development the accumulation of both ¹⁴C-sucrose and ¹⁴C-BA in the ear increased but the ¹⁴C-BA distribution pattern (ratio of the internode/kernel and the rest of the ear) did not change significantly. In the period of one to two weeks after anthesis the accumulation of ¹⁴C-sucrose and ¹⁴C-BA was higher in the kernels of the Slavia cv., i.e. in the cultivar with a higher mass of kernels.     

Pre-anthesis Interaction of Cytokinins and ABA in the Transport of 14C-sucrose to the Ear of Winter Wheat (Triticum aestivum L.)

The effect of the application of abscisic acid (ABA, 10⁻⁴ mol 1⁻¹), benzyl adenine (BA, 10⁻⁶ mol - 1⁻¹), N⁶-m-hydroxybenzyl-adenosine (HBA, 10⁻⁶ mol - 1⁻¹) and combinations of these cytokinins with ABA on the transport of ¹⁴C-sucrose into the developing kernels of winter wheat, their number and mass, was studied. Growth substances were applied in the period 10 to 5 days before anthesis and their effects were examined 4 and 18 days after anthesis on ears that were detached 10 days before anthesis and then cultivated on a complete nutrient solution. The stimulating effect of HBA on the transport of ¹⁴C-sucrose, number of kernels and their mass was higher than that of BA. ABA partly decreased the stimulating effect of cytokinins and reduced up to several days after anthesis the transport of ¹⁴C-sucrose to the developing kernels, their number and mass. The results revealed that a higher level of cytokinins in the period before anthesis could effectively interact with the inhibiting effect of ABA in that period and influence the accumulation of assimilates in the kernels.     

Translocation of 14C-sucrose within the Ear in Durum and Aestivum Wheat Varieties

Excised ears of Triticum durum (HD 4502 and B 449) and T. aestivum (Kalyansona and Kundan) varieties were cultured in ¹⁴C-sucrose, and the uptake and distribution of ¹⁴C within the ear was examined. Species-level differences in the distribution of ¹⁴C to spikelets at basal, middle and apical positions in the wheat ear (vertical distribution) were observed. T. aestivum var. Kalyansona and Kundan showed no limitation in vertical translocation of ¹⁴C-sucrose, whereas in T. durum there was a decrease in the distribution of ¹⁴C to apical spikelets. Within a spikelet, the distribution of ¹⁴C-sucrose to distal grains was significantly less than that to proximal grains in all the genotypes.     

Genotypische Unterschiede in der Translokation von zwischengelagertem 14C aus dem Halm in die Körner bei Sommerweizen (Triticum aestivum L.)

Genotypic differences in the translocation of temporarily stored ¹⁴C from the stem to the grains in spring wheat (Triticum aestivum L.)
In three field experiments with two spring wheat genotypes (Kolibri and breeding line 93117 ), changes in the total nonstructural carbohydrates (TNC) of the stem were observed after anthesis. Maximum values were measured in the third or fourth week following anthesis when stems contained 300 to 400 mg TNC. Thereafter TNC content declined up to maturity.
Flag leaves of individual shoots or all plants in micro-plots were labelled with ¹⁴C 5 days prior to anthesis, at anthesis or 5 days after anthesis to observe long term movements of assimilates during grain filling. After a chase period of two to three days, 60 to 80 % of total ¹⁴C recovered in the shoot was in the stem. From total ^l4C recovered two to three days after labelling, Kolibri had translocated 12.5 to 27.0 % into the grains by maturity whereas this portion was significantly higher for the breeding line 93117 (22.5 to 43.9 %). It was concluded that genotypes differ in the translocation of soluble carbohydrates from the stem to the grains. These differences were not related to parameters describing the 'source-sink' relationship, such as leaf area, grain number or grain size. However, the lower translocation rates of Kolibri coincided with a lower TNC concentration in the stem dry matter. This was due to a higher stem weight at anthesis, a longer period of stem elongation and a higher incorporation of assimilates into structural carbohydrates in non elongating stem parts after anthesis. It was therefore suggested that the accumulation of TNC in the stem and the remobilisation of these reserves for grain filling are determined partly by factors related to the carbohydrate metabolism in the stem.     

施氮水平对冬小麦旗叶光合特性的调控效应

在大田试验条件下,对大穗型小麦品种兰考矮早八旗叶光合特性及氮素调控效应进行了研究。结果表明,旗叶叶绿素含量随籽粒灌浆进程呈逐渐降低的趋势。PSⅡ潜在活性、PSⅡ光化学的最大效率、荧光光化学猝灭系数等随生育进程呈先升高后降低的变化趋势,且均在开花期达到最大值,之后逐渐下降;荧光非光化学猝灭系数则在成熟期达到最大值。氮肥对旗叶光合特性有一定的调控效应,Chl,F_v/F_o,F_v/F_m及qP均随施氮水平的增加呈增加的趋势,其中Chl和F_v/F_o以N3（180 kg hm^-2）处理最大,F_v/F_m和qP（除孕穗期外）以N4（360 kg hm^-2）处理最大;qN则随施氮水平增加呈降低的趋势,以N4处理最小。适宜的施氮量（180 kg hm^-2）改善了兰考矮早八的光合色素性状,提高PSⅡ潜在活性及PSⅡ光化学的最大效率,减少荧光非光化学猝灭系数,从而有助于籽粒产量的提高。     

花后灌水对小麦籽粒品质性状及产量的影响

在池栽防雨条件下,研究了小麦花后不同灌水时期、不同灌水次数对籽粒产量及品质性状的影响。结果表明,在花前限量灌水条件下（135 mm）,花后灌水（45～90 mm）可显著提高小麦籽粒产量及蛋白质产量;虽然多数品质性状在花后不灌水（CK）条件下获得最大值,但灌1水未引起品质性状的明显变化;随灌水次数增加,各品质性状变劣     

不同生育时期施氮对冬小麦氮素分配及叶片代谢的影响

通过＾１５Ｎ示踪结合叶片代谢变化研究二棱期,雌雄蕊原基形成期和四分体期分别施氮对冬小麦籽粒产量和蛋白质含量的影响机理。结果表明：四分体形成期和雌雄蕊原基形成期施氮处理,收获期营养器官中＾１５Ｎ原子百分超显著降低,籽粒中＾１５Ｎ原子百分超明显增加,并提高了开花后叶片硝酸还原酶活性和叶片衰老后期的光合作用速率,显著增加了籽粒产量和籽粒蛋白质含量。     

施氮水平对两个冬小麦品种面粉色泽及面条品质的影响

在大田条件下,研究了不同施氮水平对豫麦49-198和兰考矮早八面粉色泽及面条品质的影响。结果表明,两品种面粉及面糊的色泽等级值(CGV)、红色度(a*)和黄色度(b*)随施氮量的增加而增大,亮度(L*)随施氮量的增加而下降。随着放置时间的延长,面片的CGV、a*、b*升高,而L*值下降。质构仪分析表明,随着施氮量的增加,两品种面条的硬度、黏合性、咀嚼性呈上升趋势,以360 kg hm^-2处理的值最高,并且和其他处理之间的差异达显著水平。     

冀东冬小麦灌浆期与千粒重的试验研究

通过对195份冬小麦资源品种（系）的抽穗期、灌浆时间与千粒重的试验分析表明；冀东冬小麦的抽穗期主要在5月1－14日，而5月7－12日是抽穗的高峰期，达到总量的80．4％；灌浆时间在35－45d之间，以37－41d的品种最多，占品种总数的88．2％。随抽穗的推迟、灌浆期的缩短，千粒重呈显著下降趋势，相关系数分别为r=-0.4365和r=0.8924.     

施用不同种类硫肥对豫麦49产量和品质的影响

于2000－2002年在土壤有效硫含量为15.8 mg.kg^-1的大田试验条件下,不同种类硫肥以60 kg.hm^-2纯S施入,研究了施用不同硫肥对冬小麦产量及品质的影响。结果表明,施用硫肥处理使小麦在籽粒灌浆中后期明显保持较高的群体光合速率(CAP),在灌浆后期,不施硫肥处理的小麦CAP分别低于施硫磺粉、石膏、过磷酸钙、硫铵、硫酸钾各处理9.8%、13.3%、11.9%、40.3%和43.7%。施硫提高了小麦旗叶硝酸还原酶（NR）活性,增大了生育后期的物质积累,实现了生物积累量和收获指数的同步提高,最终显著提高了粒重和籽粒产量;施硫促进籽粒灌浆过程中的麦谷蛋白积累量,且对淀粉糊化参数指标如糊化温度、低谷粘度、高峰粘度和最终粘度影响较大,有利于改善小麦品质。在本试验条件下,增施不同种类硫肥对豫麦49产量和品质均有促进效果,其中以过磷酸钙效果较佳。     

Recovery of 15N-Labelled Urea Applied to Wheat (Triticum aestivum L.) in the Ethiopian Highlands as Affected by P Fertilization

Soil degradation and depletion of soil nutrients are among the major factors threatening sustainable cereal production in the Ethiopian highlands. Fertilizer use as a means of mitigating nutrient depletion has become widely accepted. The fate of fertilizer nitrogen (N) applied to a semidwarf bread wheat system was determined in microplots receiving 41 kg N ha^?1 in the form of urea labelled with 5.617 % atom excess ¹⁵N, without and with the application of phosphorus (P) at 20 kg P ha^?1. The study was conducted in three different agro‐ecological zones at 2200, 2400 and 2800 m above sea level (masl) (Kulumsa, Asasa and Bekoji, respectively) in the south‐eastern Ethiopian highlands. Yield and yield response to N diminished with elevation, while the response to P increased with elevation, with a significant increase in wheat grain yield observed at Bekoji (2800 masl). N harvest index and N use efficiency improved in response to P application at Asasa (2400 masl). Crop removal accounted for 25–64 and 36–64 % of the applied N without and with P, respectively. The corresponding fractions of ¹⁵N recovered in the soil ranged from 2.9 to 3.5 % and from 3.2 to 3.7 %, respectively. Recoveries of applied ¹⁵N were 67 and 52 % at Kulumsa and Asasa, but only 25 % at the highest elevation site, Bekoji. Fertilizer P significantly enhanced N recovery at Asasa (60 %) and Bekoji (36 %), but not at Kulumsa, where the soil had a high level of residual P from previous applications. The fraction of ¹⁵N recovered in the soil–plant system was rather low at Bekoji. However, the rate of ¹⁵N recovery was significantly improved (by 37 %) when fertilizer P was added to the soil. Across all locations, the unaccounted ¹⁵N may have been lost primarily through denitrification and volatilization.     

Assimilation, Dissimilation and Accumulation of 14C in Two Maize (Zea mays L.) Hybrids of Different Drought Tolerance

The effects of exposure in the vegetative phase of growth to 5- or 10-day spells of soil drought (30% field water capacity) on assimilation, dissimilation and accumulation of ¹⁴C and on dry matter growth were studied in two maize hybrids, nos. 8344 and 8388 (Garst Seed Co.) of high and low drought tolerance. Under control water regime in soil there was no difference in ¹⁴CO₂ uptake and dry matter growth between hybrids. After five days of drought ¹⁴CO₂ assimilation dropped by about 75% referred to unit weight of dry matter in hybrid 8344 and by 56% in hybrid 8388. After 10 days of drought ¹⁴CO₂ assimilation rate was reduced by 75% in both hybrids. Soil drought increased the ¹⁴C dissimilation. There were no significant differences between hybrids in all treatments, with the exception of 5 days drought; after this treatment the dissimilation rate of hybrid 8344 was higher than that of 8388. Changes of translocation of ¹⁴C and its accumulation in particular organs occurred in drought treated plants; the amount of ¹⁴C accumulated in roots of plants of hybrid 8344 increased, while that of hybrid 8388 decreased. Changes of ¹⁴C accumulation in roots were positively correlated to changes of dry matter of those organs. One day after 10 days of drought assimilation and dissimilation rates in both hybrids were about 60% of controls.     

Slow Export of Photoassimilate from Stay-green Leaves during Late Grain-Filling Stage in Hybrid Winter Wheat (Triticum aestivum L.)

Hybrid winter wheat (cv. XN901) shows a strong hybrid vigor in terms of yield potential and its leaves and stems stay green when its kernels reach maturity. Much of its pre-stored carbon reserve is left unused in its stems and leaves. In this study, photosynthesis and translocation of carbon assimilates of the hybrid wheat were investigated at its late grain-filling stage. Feeding labelled ¹⁴CO₂ to flag leaves of XN901 showed that its export to grains was much slower than that of an ordinary cultivar (Shaan 229) that is currently used in production. Within 24 h of labelling, Shaan 229 and XN901 exported 59 % and 40 %, respectively, of the ¹⁴C from their flag leaves. At the sink side, 52.1 % of the fed ¹⁴C in Shaan 229 was exported to its grains within the first 24 h while XN901 deposited only 15.8 % of the fed ¹⁴C in the grains at the same period. Photosynthetic rates and chlorophyll contents in the flag leaves declined much more slowly in XN901 than in Shaan 229 during the late grain-filling stage. Hybrid wheat XN901 also had a longer grain-filling period (6 days longer), higher grain yield (15 % more), but lower harvest index (19 % less) than Shaan 229. Its grain-filling rate was lower but declined more slowly at the late grain-filling stage than that of Shaan 229. Results indicate that the strong hybrid vigour of XN901 leads to an unfavourably delayed senescence which results in the much unused carbon reserve in its straws. Raising harvest index should be the key aim to materialize its yield potential.     

硫肥对两个不同穗型冬小麦品种光合特性及产量的影响

在大田土壤有效硫含量15.8 mg.kg^-1试验条件下，研究了不同硫肥处理对冬小麦多穗型品种豫麦49和大穗型品种豫麦66光合特性和产量的影响。结果表明，60 kg.hm^-2纯硫基施或基施与拔节期追施各50%处理与对照相比，提高了群体光合速率（CAP）、旗叶蒸腾速率（T_r），同时提高了叶片叶绿素（Chl）含量，尤其显著地提高了旗叶净光合速率（P_n），延缓了灌浆后期P_n的下降。施硫处理产量显著高于对照，以60 kg.hm^-2纯硫分基施与拔节期追施各50%处理效果最好。两品种光合特性和产量对不同硫肥处理的反应表现出差异，施硫对豫麦66旗叶光合速率的影响大于豫麦49。纯硫120 kg.hm^-2处理的光合特性指标和产量低于其他硫肥处理。据此，作者对两种穗型冬小麦品种合理施用硫肥的技术措施提出了建议。     

Effects of soil drought during the vegetative phase of seedling growth on the uptake of 14co2 and the accumulation and translocation of 14C in cultivars of field bean (vicia faba L. Var. Minor) and field pea (pisum sativum L.) Of different drought tolerance

During the vegetative phase of growth of two field bean and two field pea cultivars of different drought tolerance, the effect of short and prolonged soil drought on gas exchange (CO₂ i H₂O), leaf water potential (ψ), stomatal diffusive resistance (r_S), uptake of CO₂, and the distribution and accumulation of ¹⁴C was studied. Differences in the response to drought conditions between resistant and susceptible cultivars were marked. After 5 days of soil drought, the decrease in net photosynthesis and transpiration rate and the increase of stomatal resistance were greater in the drought-resistant cultivars than in the drought-susceptible ones. In contrast, after 10 days of drought the decrease of leaf P_N (CO₂ assimilation rate), E (rate of transpiration) and ψ (water potential) was greater in the susceptible cultivars than in the resistant ones. Significant differences between the resistant and the susceptible cultivars were also observed in the assimilation and translocation of ¹⁴C by the green parts of the plant. The amount of carbon accumulation in roots in drought-susceptible cultivars increased less than in the drought-resistant cultivars. For treatments in which optimal soil watering was resumed after 5 or 10 days of drought there was no evidence of effects of drought on the majority of measurements, but the drought-resistant cultivars showed a general tendency for a more rapid recovery. Our results confirm the existence of genetic variability in drought tolerance among the cultivars of field bean and field pea. The recorded differences in the response to drought of experimental cultivars may indicate that, under water deficit in the soil and in plant tissues, they may use different strategies to avoid the damaging effects of temporary limitation of water supply; for example, the drought-resistant cultivars may more effectively conserve tissue hydration through effective stomatal closure. Also, the observed changes in carbon assimilation and accumulation might be the reason for their different responses to drought. The change in radioactivity losses in the control and stressed plants may result from the differences in demand for energy to maintain cell structure and function. Similarly, the less intense carbon accumulation in the roots of the sensitive cultivars could be caused by more harmful effects of drought on root growth.     

Growth Properties and Ion Distribution in Different Tissues of Bread Wheat Genotypes (Triticum aestivum L.) Differing in Salt Tolerance

Four bread wheat genotypes differing in salt tolerance were selected to evaluate ion distribution and growth responses with increasing salinity. Salinity was applied when the leaf 4 was fully expanded. Sodium (Na⁺), potassium (K⁺) concentrations and K⁺/Na⁺ ratio in different tissues including root, leaf‐3 blade, flag leaf sheath and flag leaf blade at three salinity levels (0, 100 and 200 mm NaCl), and also the effects of salinity on growth rate, shoot biomass and grain yield were evaluated. Salt‐tolerant genotypes (Karchia‐65 and Roshan) showed higher growth rate, grain yield and shoot biomass than salt‐sensitive ones (Qods and Shiraz). Growth rate was reduced severely in the first period (1–10 days) after salt commencements. It seems after 20 days, the major effect of salinity on shoot biomass and grain yield was due to the osmotic effect of salt, not due to Na⁺‐specific effects within the plant. Grain yield loss in salt‐tolerant genotypes was due to the decline in grain size, but the grain yield loss in salt‐sensitive ones was due to decline in grain number. Salt‐tolerant genotypes sequestered higher amounts of Na⁺ concentration in root and flag leaf sheath and maintained lower Na⁺ concentration with higher K⁺/Na⁺ ratios in flag leaf blade. This ion partitioning may be contributing to the improved salt tolerance of genotypes.     

Intraspecific Variation in Nitrogen Uptake and Nitrogen Utilization Efficiency in Wheat (Triticum aestivum L.)

Twenty wheat ( Triticum aestivum L.) varieties differing in plant height were grown in soil culture and evaluated for differences in nitrogen uptake and nitrogen utilization efficiency (NUE) at limited (40 kg N ha⁻¹) and normal (120 kg N ha⁻¹) nitrogen supply. Nitrogen uptake showed 1.4- and 1.5-fold varietal variation at harvest for limited and normal N supply, respectively. NUE for dry matter production (NE1) exhibited 1.28- and 1.38-fold genotypic variation while NUE for grain production (NE2) varied by 1.25- and 1.21-fold at limited and normal N supply, respectively. Tall varieties were found to have higher N uptake and NUE for dry matter production, while dwarf cultivars had greater NUE for grain production. Nitrogen uptake was found to be strongly positively associated with dry matter production (r=0.85 and r =0.77 at limited and normal N supply, respectively), indicating an important effect of growth rate on N uptake. NUE for biomass production, as well as for grain production, was reduced as the supply of nitrogen was increased.     

14CO2 Assimilation and Translocation of 14C-Photosynthates by Different Parts of Indian Mustard (Brassica juncea L.)

The role of leaves, stem and reproductive parts in ¹⁴CO₂ fixation and subsequent photosynthate translocation was studied in Indian mustard ( Brassica juncea L.) at three growth stages. The data indicated that leaves, stem and pods are important sources of photosynthates for seed filling. At bud emergence stage leaves are the principle site of ¹⁴CO₂, fixation. The contribution of leaves declines at subsequent stages, where as the contribution of pod walls increased from bud emergence stage to ripening stage. The contribution of the stem remains more or less constant at all three growth stages studied. Although stem can fix ¹⁴CO², at bud emergence and flowering stages it imported ¹⁴C-photosynthates from leaves. However, stem exported photosynthates during subsequent growth stages.