Combined effects of salinity and phosphorus availability on growth,gas exchange,and nutrient status of Catapodium rigidum

The combined effects of NaCl-salinity and phosphorus deficiency on biomass production, nutritional status, and photosynthetic activity were studied in Catapodium rigidum: an annual Poacea with fodder potential. Plants were grown in hydroponic conditions for 55 days under two phosphorus (P) supply: 5 (low) or 180?µmol KH₂PO₄ (sufficient), in the absence or presence of 100?mM NaCl. Obtained results demonstrated that both salinity and P deficiency treatments applied separately reduced substantially plant growth and CO₂ assimilation rate with a more marked impact of salt stress. Salinity has no substantial effect on both shoot P concentrations and phosphorus acquisition efficiency independently of P availability. The highest decrease in plant growth (?91%) was observed in plants simultaneously submitted to both stresses suggesting an additive effect of the two stresses and that P deficiency increased the susceptibility of C. rigidum to salinity. This may be linked to a significant decrease in potassium acquisition (?95%), K/Na selectivity ratio (?73%), stomatal conductance (?66%), CO₂ assimilation rate (?64%), and shoot water content (66%). Furthermore, plants cultivated under combined salinity and sufficient P supply displayed higher stomatal conductance, CO₂ assimilation rate, K/Na selectivity ratio, and plant growth than plants cultivated under combined effects of salinity and P deficiency. These results suggest that adding P to saline soils could be an alternative for alleviating the negative effects of salinity and may ameliorate salinity tolerance.     

磷钾肥对云南旱作马铃薯产量和养分吸收的影响

在云南省曲靖地区的低肥力和中高肥力试验地分别开展旱作马铃薯的田间小区试验,研究磷钾施用量对马铃薯生物量、养分利用、产量和经济效益的影响。结果表明：相同施肥量的条件下,中高肥力试验地的东山组马铃薯产量远高于低肥力的越州组,产量相差10305．00～20140．20 kg·hm－2;越州组NP2K3（N ,150 kg·hm－2;P2O5,90 kg·hm－2;K2O ,405 kg·hm－2）处理产量产值最高,NP2K1（N ,150 kg·hm－2;P2O5,90 kg·hm－2;K2O ,135 kg·hm－2）处理净收益最高;东山组NP2K2（N ,150 kg·hm－2;P2O5,90 kg·hm－2;K2O ,270 kg·hm－2）处理产量、产值及净收益均是最高;两组试验的马铃薯干重变化趋势相似,NP2K2处理的干重积累量较多,无钾无磷处理干重积累少;马铃薯体内累积K最多,其次为N ,最后为P ,NPK养分吸收积累的高峰期在马铃薯块茎膨大期到淀粉积累期;东山组的马铃薯PK利用效率明显高于越州组。NP1K2（N ,150 kg·hm－2;P2O5,45 kg·hm－2;K2O ,270 kg·hm－2）处理的P肥利用率和P素农学效率较高,P肥利用率和P素农学效率都有随施P量增加而降低的趋势。NP2K1处理的K肥利用率和K素农学效率最高,K肥利用率和K素农学效率均有随施K量增加而降低的趋势。     

黄土源区施加磷肥对小麦光合性能、水分利用效率及茎流速率的影响

通过陕西长武黄土塬区的田间试验,对3个磷肥施用水平(0,90、180 kg/hm2,即F0、F1和F2)下小麦的光合性能、瞬时水分利用效率及开花期植株茎流速率的变化进行了研究,分析了不同施磷水平下小麦产量的差异,对叶片蒸腾速率和植株茎流速率做了回归分析.结果显示:不同磷肥处理下叶片净光合速率日变化均为双峰曲线,上午9时...     

Extracellular Matrix, Esterase and the Phytotoxin Prehelminthosporol in Infection of Barley Leaves by Bipolaris sorokiniana

Light microscopy and cryo-scanning electron microscopy showed that hyphae of Bipolaris sorokiniana adhered to the wax surfaces of barley leaves by means of an extensive extracellular matrix (ECM). Prehelminthosporol, the major non-host specific phytotoxin formed by B. sorokiniana was immunolocalized in large amounts in the ECM surrounding the hyphae. Similarly, esterase activity involved in degradation of the cuticular wax surface was found in the ECM. Therefore, it appears that the ECM is not only important for adhesion of the fungus to its host, but also functions as a sink of phytotoxins and lytic enzymes important for infection of the host plant.     

Differential metabolic response of barley genotypes,varying in resistance,to trichothecene‐producing and ‐nonproducing (tri5−) isolates of Fusarium graminearum

Resistance of barley to Fusarium graminearum was studied using a pair each of resistant and susceptible black and yellow barley lines. The spikelets were inoculated with a trichothecene‐producing isolate, a trichothecene‐nonproducing isolate (tri5^?), or a mock solution. Spikelets were collected 72 h after inoculation and metabolites were analysed using a LC‐hybrid MS system. Metabolite abundances were used to identify the constitutive (RRC) and induced resistance‐related metabolites (RRI). The pathogen virulence factor, DON, and its plant detoxification product, DON‐3‐O‐glucoside (D3G), were also identified and designated as resistance‐indicator (RI) metabolites. The RRC, RRI and RI metabolites were putatively identified. Jasmonic acid was significantly induced in barley following inoculation with a trichothecene‐producing isolate, but not with a tri5^? isolate. The former isolate reduced the induction of both the number and amount of RR metabolites. The metabolites cinnamic acid, sinapoyl alcohol, coniferin, catechin and naringin were identified only in response to the inoculation with a tri5^? mutant. The abundances of p‐coumaric acid, coniferaldehyde and sinapaldehyde increased more in response to the tri5^? mutant than to the trichothecene‐producing isolate. The total amount of DON synthesized and its conversion to D3G varied greatly between the resistant and susceptible black barley, but not in yellow barley. Interestingly, an increase in the amount of total DON produced was associated with a decrease in the conversion of DON to D3G. The roles of RRC, RRI and RI metabolites in plant defence and their further use as potential biomarkers in screening are discussed.     

过去300年来新疆奇台县水资源利用的变化及其环境响应

针对新疆奇台县水资源短缺及其生态影响的实际问题,运用人地关系的理论与历史地理学的研究方法,关注事件的过程研究,通过重建研究区人口数量和耕地面积的增长变化,探究一个较长时段内人类利用水资源的变化过程及其对环境影响的阶段性特点。研究表明：在过去300年的时间内,奇台县的水资源利用分为三个特征性阶段：开发利用山水河时期（17...     

Consistent responses of yield and resistance of wheat cultivars to the root-lesion nematode,Pratylenchus thornei,in the Australian northern subtropical region,but not in the temperate southern region

To understand the yield response of cereal cultivars to Pratylenchus thornei, eight experiments were conducted within the subtropical northern, and temperate southern grain-producing regions of Australia. Wheat cultivars (Triticum aestivum) ranging from susceptible to moderately resistant to P. thornei were grown in Year 1 to establish a range of population densities. In Year 2 before sowing, P. thornei was quantified in each plot and six cereal cultivars were each grown on a similar range of population densities (average minimum to maximum of 3.4–60.6 P. thornei/g soil); P. thornei was quantified again at harvest. In the four experiments in the northern region there was a significant, negative logarithmic response of yield of the three most intolerant/susceptible cultivars as P. thornei population densities increased (yield decreased 172–479 kg/ha per unit increase in log_e-transformed P. thornei/g soil). The responsiveness of yield to increasing P. thornei population densities diminished as the tolerance and resistance of the cultivars improved. In the southern region, there was no relationship between yield and P. thornei in three experiments and minor, positive increases in one experiment (1.6 kg/ha per unit increase in P. thornei/g soil). Across both regions, the change in P. thornei population densities from sowing to harvest was logarithmic and positive, and generally greatest in the northern region. The contrast of responses of cereal cultivars between the regions, despite similar population densities of P. thornei, is indicative of the influence of the environment particularly on tolerance, therefore management with a regional focus is essential.