Seasonal changes in leaf nitrogen pools in two Salix species

Leaf nitrogen distribution pattern was studied four times during the growing season in a 2-year-old Salix viminalis L. and Salix dasyclados Wimm. plantation in Estonia. We measured the vertical distributions of leaf nitrogen concentration, dry mass, leaf area and light environment (as fractional transmission of diffuse irradiance, a(d)) in the canopy. The light-independent nitrogen pool was evaluated as the intercept of the leaf nitrogen concentration versus a(d) relationship, and the nondegradable nitrogen pool was evaluated as the nitrogen remaining in abscised leaves. A strong vertical gradient of mass-based leaf nitrogen concentration was detected at the beginning of the growing season, and decreased steadily during canopy development. This decline had at least three causes: (1) the amount of nitrogen in the foliage was larger at the beginning of the growing season than at the end of the growing season, probably because of pre-existing root systems; (2) with increasing leaf area index (LAI) during the growing season, the proportion of leaf nitrogen in total canopy nitrogen that could be redistributed (light-dependent nitrogen pool) decreased; and (3) the photosynthetic photon flux density gradient inside the canopy changed during the season, most probably because of changes in leaf area and leaf angle distributions. Total canopy nitrogen increased almost proportionally to LAI, whereas the light-dependent nitrogen pool had a maximum in August. Also, the proportion of the light-dependent nitrogen pool in the total canopy nitrogen decreased steadily from 65.2% in June to 17.2% in September in S. dasyclados and from 63.3 to 15.1% in S. viminalis. The degradable nitrogen pool was always bigger than the light-dependent nitrogen pool.     

Leaf photosynthetic properties in a willow (Salix viminalis and Salix dasyclados) plantation in response to fertilization

Specific leaf area (SLA), nitrogen and chlorophyll concentrations and photosynthetic characteristics were studied in upper and lower canopy leaves of Salix viminalis and S. dasyclados grown at two nutrition levels. Fertilization increased SLA and leaf mass-based nitrogen concentration in most cases. Positive effects of fertilization on leaf light-saturated photosynthetic rate (A _max ^A ) and maximum carboxylation rate (V _cmax) were not detected. Significant differences between the leaves from upper and lower canopy layers in area-based nitrogen, A _max ^A , SLA, mass-based chlorophyll, V _cmax and stomatal conductance were found for most plots. We attempted to estimate the fraction of non-photosynthetic nitrogen and found that it tended to be higher due to fertilization. Thus, the insensitivity of leaf photosynthesis to fertilization could be caused by higher proportion of non-photosynthetic nitrogen in the leaves of fertilized plots. Though leaf-level photosynthesis was not increased by fertilization, considerably higher leaf area index of fertilized plots still resulted in increased canopy carbon gain.     

甘薯细胞壁蔗糖转化酶基因IbCWIN家族成员鉴定及表达分析

甘薯是重要的粮食、饲料、工业原料作物和新型的生物能源作物,细胞壁蔗糖转化酶是植物源、库组织蔗糖代谢的关键酶,但关于甘薯细胞壁蔗糖转化酶基因IbCWIN家族成员的研究尚未见报道。本研究测定供试品种不同组织部位的蔗糖淀粉含量,利用生物信息学方法对IbCWIN基因家族的理化性质、保守结构域、系统进化关系、启动子作用元件、组织特异性表达模式进行分析。结果表明,甘薯茎中蔗糖含量最高,须根和叶次之,块根最低;块根淀粉含量最高,极显著高于其他部位。甘薯中含有10个IbCWIN基因,编码氨基酸442～1115个,蛋白质分子量范围49.56～124.44kD,等电点为5.0～9.1。分布在8条染色体上,都含有Glyco₃2保守结构域及相同或相似的保守基序motif,属于糖基水解酶基因家族GH32。IbCWIN与木薯MeCWINV同源性高, IbCWIN基因家族启动子区域含有多种类型的顺式作用元件。qRT-PCR结果表明,IbCWIN基因家族在甘薯不同组织中均有表达且有多种表达模式,其中IbCWIN2和IbCWIN9在块根中表达量显著高于其他组织部位。本研究为下一步探索甘薯IbCWI...     

The prevalence of microalbuminuria and proteinuria in cats with diabetes mellitus

The prevalence of microalbuminuria (MA) and proteinuria was evaluated in 66 cats with diabetes mellitus (DM), 35 nondiabetic cats with other illness, and 11 healthy nondiabetic cats with use of the E.R.D.-HealthScreen Feline Urine Test. The MA prevalence was higher in the diabetic than in the nondiabetic sick and healthy control cats (70%, 39%, and 18% respectively, P < .0001). In addition, prevalence of proteinuria defined by a protein/creatinine ratio (UPC) > 0.4 was significantly higher in the diabetic cat than in the control cats (70%, 35%, and 9% respectively, P < .0001). There was a significant but weak correlation between the results of MA and UPC (P < .0001, r = 0.43). Our results showed that MA is common in cats with DM. Further studies are required to evaluate the prognostic value of the presence and the severity of MA in cats with DM.     

Urinalysis interpretation: how to squeeze out the maximum information from a small sample

The urinalysis is an essential part of the diagnostic evaluation for all urinary and many metabolic diseases. Its assessment includes evaluation of physical characteristics (color, clarity, and volume), biochemical parameters (urine pH, blood, glucose, ketones, bilirubin, urobilinogen, and protein) and microscopic sediment evaluation (RBC, WBC, organisms, epithelial cells, crystals, and casts). Many of these parameters are influenced by collection method and therefore, it is essential to interpret accordingly. Knowledge of factors that can interfere with the accuracy of some test results can decrease improper interpretation. When all of these parameters are evaluated in combination with clinical signs, physical examination, thorough history and other laboratory tests, a diagnosis will often be attained.     

Estimation of shoot biomass productivity in Estonian Salix plantations

Shoot biomass production was estimated in two Estonian short rotation forest (SRF) plantations during the first rotation cycle (1994–1997). The plantations were established with six clones of Salix viminalis and one clone of Salix dasyclados in 1993. The plantation, located on well-composed organic soil, was characterised by higher productivity (6.2 t DM ha⁻¹ per year) compared with the plantation on poor mineral soil (5.2 t DM ha⁻¹ per year). Fertilisation of the latter plantation increased its productivity to 11.0 t DM ha⁻¹ per year, which is the value close to a predicted maximum for Swedish climatic conditions. In fertilised plots, clone 81090 of S. dasyclados was characterised by the highest productivity among all clones, but also by high stool mortality. Clones 78021 and 78183 of S. viminalis had the most stable and relatively high productivity and can therefore be recommended as promising planting material for SRF in Estonia.

When estimating production, the use of proper allometric relations between shoot dry weight and diameter is of crucial importance. Additional measurements on 1-year-old shoots in 1998 showed that besides shoot age also clone and fertilisation are significant factors influencing allometric relations. The dry weight of fertilised shoots was about 10% lower than that of non-fertilised shoots of the same height and diameter. Older shoots were heavier than younger shoots with a similar diameter.     

Quantitative trait locus analysis of wheat quality traits

Milling and baking quality traits in wheat (Triticum aestivum L.) were studied by QTL analysis in the ITMI population, a set of 114 recombinant inbred lines (RILs) generated from a synthetic-hexaploid (W7985) × bread-wheat (Opata 85) cross. Grain from RILs grown in U.S., French, and Mexican wheat-growing regions was assayed for kernel-texture traits, protein concentration and quality, and dough strength and mixing traits. Only kernel-texture traits showed similar genetic control in all environments, with Opata ha alleles at the hardness locus Ha on chromosome arm 5DS increasing grain hardness, alkaline water retention capacity, and flour yield. Dough strength was most strongly influenced by Opata alleles at 5DS loci near or identical to Ha. Grain protein concentration was associated not with high-molecular-weight glutenin loci but most consistently with the Gli-D2 gliadin locus on chromosome arm 6DS. In Mexican-grown material, a 2DS locus near photoperiod-sensitivity gene Ppd1 accounted for 25% of variation in protein, with the ppd1-coupled allele associated with higher (1.1%) protein concentration. Mixogram traits showed most influence from chromosomal regions containing gliadin or low-molecular-weight glutenin loci on chromosome arms 1AS, 1BS, and 6DS, with the synthetic hexaploid contributing favorable alleles.Some RI lines showed quality values consistently superior to those of the parental material, suggesting the potential of further evaluating new combinations of alleles from diploid and tetraploid relatives, especially alleles of known storage proteins, for improvement of quality traits in wheat cultivars.Contribution number 06-77J from the Kansas Agricultural Experimental Station.