甜菜当年抽薹过程中脂肪酸和蛋白质水解氨基酸组分的变化

对GA3和温光诱导当年抽薹的甜菜与当年抽薹甜菜品种进行研究,探讨当年抽薹过程甜菜中脂肪酸和蛋白质水解氨基酸组分的变化。结果表明:无论是诱导当年抽薹,还是当年抽薹的品种,在抽薹过程中饱和脂肪酸(棕榈酸+硬脂酸)含量迅速上升;不饱和脂肪酸(油酸、亚油酸和亚麻酸)含量下降;饱和脂肪酸和不饱和脂肪酸的含量分别由棕榈酸和亚麻酸的含量决定。甜菜当年抽薹过程中,蛋白质含量和氨基酸总量均增加。蛋白质氨基酸中Glu、Gly、Ala、Met、Asp、Ser、Thr、Lys、Lue等氨基酸组分变化规律一致,抽薹前至抽薹时先升高,抽薹后又迅速下降,与不抽薹的对照非常接近。抽薹可能与这些氨基酸的变化有关。     

LEAF PHOTOSYNTHESIS,BIOMASS PRODUCTION AND WATER AND NITROGEN USE EFFICIENCIES OF TWO CONTRASTING NAKED VS. HULLED OAT GENOTYPES SUBJECTED TO WATER AND NITROGEN STRESSES

Water and nitrogen (N) are the two most important factors influencing the growth and yield of oat (Avena sativa). A pot culture study was conducted to determine the physiological and biomass production of contrasting oat genotypes to water and N supply conditions. With sufficient water, biomass yield of the naked ‘Shadow’ was 12.4% and 10.0% greater than ‘Bia’ in the treatments 750 and 1250 mg N pot^?1, respectively, but ‘Bia’ produced greater grain yield than ‘Shadow’. Under severe water stress conditions, increasing N supply decreased P_N mainly due to the reduction of g_s and E. ‘Shadow’ had higher chlorophyll and leaf N than ‘Bia’, while there were no differences in plant total N, NuptE and NUE. With increasing N application and water stress, WUE_L and WUE_P both increased. NUE was inversely related with increasing N rates and water stress levels, resulting in a trade-off relationship between WUE_P and NUE.     

热胁迫下丹参迷迭香酸代谢途径关键酶基因的表达研究

为探索热胁迫对丹参迷迭香酸途径关键酶基因表达的影响,采用定量RT-PCR法,以Actin与GAPDH作为内参基因,0~48h叶片cDNA作为模板,对迷迭香酸途径7个关键酶基因PAL、C4H、4CL、TAT、HPPD、HPPR和RAS的表达进行分析。通过试验结果构建出这7个关键酶基因0~48h代谢途径表达图谱。其中,PAL、C4H和RAS受热胁迫影响表达量下降;TAT、4CL和HPPD表达量呈先上升后下降趋势;HPPR表达量前期变化不大,后期呈下降趋势。结果表明热胁迫对迷迭香酸途径关键酶基因表达有极显著影响。该表达时序谱的建立为进一步研究热胁迫与酚酸类成分累积之间的关系奠定了基础。     

ALLOCATION OF NITROGEN AND DRY MATTER FOR TWO SOYBEAN GENOTYPES IN RESPONSE TO WATER STRESS DURING REPRODUCTIVE GROWTH

Drought stress significantly limits soybean [Glycine max (L.) Merr.] yield in the Southeastern United States. The Plant Introduction 416937 (PI), which has lower yields than adapted cultivars under favorable conditions but a relatively lesser yield reduction under water-stress conditions, has been identified as a potential source of drought avoidance germplasm. It is unclear whether the mechanism of drought avoidance is associated with shoot or root. Also unclear is the effect of the PI's restricted yield potential on the extent of its yield reduction in response to a water stress. To determine the differences in response between the PI and an adapted cultivar, Deltapine 105, to reproductive sink size and water stress, inoculated PI and Deltapine plants were grown in sand-filled pots in controlled-environment chambers. The fixed rooting volume of the pot culture restricts the influence that genotypic differences in rooting patterns may have in accessing soil water. During the 24-day period of pod development between R-3 and R-6 growth stages, plants were subjected to one of two water regimes, either well-watered or water-stressed to a leaf water potential of about ?0.95 MPa. Within each water treatment, plants of both genotypes were depodded at the R3 stage to remove all pods (full depodding), one-half of the pods (partial depodding), or no pods (no depodding). Tissues of plants harvested at the R6 stage were separated, dried to a constant mass, weighed, and analyzed for nitrogen. Photosynthate production was calculated from dry matter and nitrogen content. Photosynthate production and nitrogen fixation by Deltapine plants were unaffected within a pod load by the mild water stress, but both photosynthate production and nitrogen fixation by the PI plants were diminished by the mild water stress except when a reproductive sink was absent. It thus appears that a sizeable component of the drought tolerance observed in field experiments for the PI plants may be attributed to root characteristics. Leaf nitrogen concentration decreased during water stress in Deltapine plants but not in the PI plants. Also, the decrease in nitrogen concentration in stems was greater in response to increased reproductive load for Deltapine plants than for the PI plants. These data suggest that the PI does not remobilize leaf nitrogen as readily as Deltapine.     

MEASUREMENT OF LOSSES FROM FERTILIZER NITROGEN DURING INCUBATION IN ACID SANDY SOILS AND DURING SUBSEQUENT GROWTH OF RYEGRASS, USING 15N-LABELLED FERTILIZERS

Ammonium sulphate and calcium nitrate both containing excess ¹⁵N were applied to four acid sandy soils; two were from old arable fields and two from grassland, selected so that one of each pair was about pH 5 and the other about pH 6 (in water). The soils were incubated for 6 weeks at 21°C in large glazed earthenware pots, one set with the nitrification inhibitor 2-chloro-6-(trichloromethyl)-pyridine added and another without inhibitor. Ammonium and nitrate N were determined at intervals, and the total-N at the start and after 6 weeks. The atom per cent ¹⁵N in the mineral-N extracted from soils treated with ammonium sulphate was determined after 0, 3, and 6 weeks, and in the total-N of all the soils given N-fertilizer at 0 and 6 weeks. Much added N was immobilized at first, but some was re-mineralized during the second half of the incubation. Mineral-N extracted from soils treated with ammonium sulphate contained less ¹⁵N than the fertilizer added, showing that part of the apparent re-mineralization during the second half was from unlabelled soil organic matter. After incubating for 6 weeks less than 5 per cent of the N added as nitrate was lost but about 5 per cent of the labelled-N added as ammonium sulphate was lost from the two grassland soils. Adding the inhibitor prevented this loss. After incubating, the soil remaining in each jar was halved to provide duplicate pots and sown with ryegrass. A similar series of pots with the same treatments (but with unlabelled fertilizer) was also prepared from the soils that had been stored slightly moist and at 21°C; these were sown with ryegrass. All pots were harvested after 42 days and again after 70 days. More than 93 per cent of the labelled-N was recovered in plants and soil, except from the two grassland soils to which calcium nitrate was added. It is concluded that while a little nitrogen may be lost during nitrification in some of these soils, more nitrogen may be lost during the growth of grass, when nitrate is present in relatively large amounts. The nitrification inhibitor decreased yields of grass at the first cutting on grassland soils treated with ammonium, but increased them on soil treated with nitrate, suggesting that changing the proportions of nitrate to ammonium by adding the inhibitor alters the growth rate and yield of grass.     

近20年太湖流域典型区土壤养分时空变化及驱动机理

长期的定位采样试验研究了近 2 0年锡山市甘露乡土壤表层 ( 0～ 2 0cm)中有机质、全氮、速效氮、速效磷、速效钾等土壤养分的时空变化趋势 ,并分析了土壤养分波动与国家政策、耕作方式、农业投入和单位面积农业纯收益之间的相互关系。结果表明 :2 0年间土壤养分质量总体上呈现先减后增的变化趋势。有机质呈现先减后增的变化趋势 ,且与耕作措施的改变有密切关系。全氮和速效氮呈持续上升趋势 ,上升幅度大于 1 0 0 % ,与氮肥使用量不断上升密切相关。速效磷、速效钾呈持续下降趋势 ,与磷肥、钾肥使用过少有关。国家政策和耕作方式、种植制度对SNQI影响十分明显 ,标准农业投入与土壤养分质量指数呈正相关关系 ,单位面积标准农业纯收益与土壤养分质量指数呈负相关关系