PEG-6000干旱胁迫对沙芦草种子萌发特性的影响及其抗旱性评价

采用不同浓度PEG-6000模拟干旱胁迫的方法对7份不同来源的沙芦草种质的种子萌发特性及其抗旱性进行鉴定和评价.结果表明:不同浓度PEG-6000胁迫对沙芦草种子的相对发芽率、相对发芽势、相对抗旱指数、相对活力指数、相对幼苗长、相对幼苗重均有明显抑制作用;低浓度PEG-6000干旱胁迫对相对幼根长具有促进作用,高浓度具有抑制作用.在PEG干旱胁迫下,7份沙芦草种子的相对发芽率、相对发芽势、相对幼苗长和相对根长差异较大,而相对抗旱指数、相对活力指数和幼苗重差异较小.通过隶属函数法综合评价认为,7份沙芦草种质材料的抗旱性顺序依次为3号＞7号＞2号＞4号＞6号＞l号＞5号材料.     

Conservative stocking or maximum profit: A grazing management dilemma?

Abstract

Swards in the False Thornveld of the Eastern Cape are generally stocked considerably in excess of the rate currently recommended for maximised production on a sustained basis. Economic analysis of the relationship between stocking rate and production per ha reveals that there is no financial justification for such heavy stocking. Moreover, conservative stocking rates increase the farmer's ability to withstand drought without adversely affecting profit. Veld condition also plays a considerable role in determining financial return per ha. Despite these observations, farmers continue to stock heavily and this is accompanied by veld deterioration. A possible explanation is that the productive value of land is relatively insignificant when compared with its investment value.     

Effect of calf death loss on cloned cattle herd derived from somatic cell nuclear transfer: Clones with congenital defects would be removed by the death loss

To increase public understanding on cloned cattle derived from somatic cell nuclear transfer (SCNT), the present review describes the effect of calf death loss on an SCNT cattle herd. The incidence of death loss in SCNT cattle surviving more than 200 days reached the same level as that in conventionally bred cattle. This process could be considered as removal of SCNT cattle with congenital defects caused by calf death loss. As a result of comparative studies of SCNT cattle and conventionally bred cattle, the substantial equivalences in animal health status, milk and meat productive performance have been confirmed. Both sexes of SCNT cattle surviving to adulthood were fertile and their reproductive performance, including efficiency of progeny production, was the same as that in conventionally bred cattle. The presence of substantial equivalence between their progeny and conventionally bred cattle also existed. Despite these scientific findings, the commercial use of food products derived from SCNT cattle and their progeny has not been allowed by governments for reasons including the lack of public acceptance of these products and the low efficiency of animal SCNT. To overcome this situation, communication of the low risk of SCNT technology and research to improve SCNT efficiency are required.     

Problems of Display Postures in the Charadrii (Aves: Charadriiformes)

Studies of displays in the Charadrii (= waders or shorebirds) show that the same posture in different species, even quite closely related, may have a different function in a given context. As a corollary to this, two species even in the same genus may have quite different display postures to convey the same message. The problem is thus twofold: (a) to interpret the function of the display in the bird's world and (b) to trace the evolution of the display within a single well-defined suborder of birds such as the Charadrii. Threat displays are especially informative in such studies, but courtship, distraction and other displays are also useful. The value of display postures in the systematics of the waders is discussed.     

The impact of fish and drought on frog breeding in temporary waters in Zimbabwe

The breeding of frogs in four ponds near Harare, Zimbabwe, was investigated during a wet rainy season (2000/01) and a dry one (2001/02). During 2000/01 eight and nine species bred in two ponds in abandoned gravel pits that never contained fish, but only four species bred in these in 2001/02 and the relative abundance was reduced by about 50%. Pond 3 was a small dam that filled after the rains and was invaded by fish once it overflowed. Five species bred in it in 2000/01, but breeding activity was curtailed once it was invaded by catfish, Clarias gariepinus, some of which were found with frog remains in their stomachs. The pond did not overflow in the following season, and was therefore not invaded by fish; although only four species bred in it their relative abundance was considerably higher. Pond 4 was a permanent pond that always contained fish. Only three species bred in it and the relative abundance of tadpoles was always low. Species belonging to the Ranidae seemed to be most severely affected by drought and this may explain the absence of some species, such as the African bullfrog, Pyxicephalus adspersus, that was once abundant around Harare.     

Natural durability of wood of ten native species from northeastern Mexico

Thorn scrub vegetation in Mexico is distributed over 50 million ha, where native tree species are the source of forage, timber, firewood and charcoal. Research describing wood durability of species from this vegetation type has not been fully determined, nor classified according to international standards. Thus, the aim of this study was to determine and classify the natural durability of ten woody species. Their natural durability was determined according to the European Pre-Norm 807, the loss of dynamic modulus of elasticity (MOEdyn) (MPa) was determined and wood mass loss (g) after being exposed to Trametes versicolor and Coniophora puteana fungi. Wood durability was classified according to the European Norm 350-1. Highly significant differences (p<0.001) were found between the durability of woody species. The more durable species with lower MOEdyn lost were Condalia hookeri (57.5%±0.6%), Havardia pallens (58.2%±0.4%) and Acacia schaffneri (58.9%±6.3%). Species with lower mass loss after exposed to Coniophora puteana were Ebenopsis ebano (6.3%±1.9%), Condalia hookeri (8.6%±2.3%) and Cordia boissieri (11.8%±2.3%). E. ebano (7.1%±2.4%), Condalia hookeri (8.2%±2.5%) and Cordia boissieri (11.5%±3.1%) showed the lower mass lost after exposed to T. versicolor. According to European Norm 350-1, three woody species were classified as very durable and durable species.     

Mapping of QTLs for Germination Characteristics under Non-stress and Drought Stress in Rice

Identification of genetic factors controlling traits associated with seed germination under drought stress conditions, leads to identification and development of drought tolerant varieties. Present study by using a population of F2：, derived from a cross between a drought tolerant variety, Gharib （indica） and a drought sensitive variety, Sepidroud （indica）, is to identify and compare QTLs associated with germination traits under drought stress and non-stress conditions. Through QTL analysis, using composite interval mapping, regarding traits such as germination rate （GR）, germination percentage （GP）, radicle length （RL）, plumule length （PL）, coleorhiza length （COL） and coleoptile length （CL）, totally 13 QTLs were detected under pole drought stress （-8 MPa poly ethylene glycol 6000） and 9 QTLs under non-stress conditions. Of the QTLs identified under non-stress conditions, QTLs associated with COL （qCOL-5） and GR （qGR-1） explained 21.28% and 19.73% of the total phenotypic variations, respectively Under drought stress conditions, QTLs associated with COL （qCOL-3） and PL （qPL-5） explained 18.34% and 18.22% of the total phenotypic variations, respectively. A few drought-tolerance-related QTLs identified in previous studies are near the QTLs detected in this study, and several QTLs in this study are novel alleles. The major QTLs like qGR-1, qGP-4, qRL-12 and qCL-4 identified in both conditions for traits GR, GP, RL and CL, respectively, should be considered as the important and stable trait-controlling QTLs in rice seed germination. Those major or minor QTLs could be used to significantly improve drought tolerance by marker-assisted selection in rice.     

Estimation of endogenous protein and amino acid ileal losses in weaned piglets by regression analysis using diets with graded levels of casein

Background

Many studies have investigated endogenous loss of proteins and amino acids (AAs) at the ileal level in growing pigs. However, only a few studies have researched this subject in piglets. Knowledge regarding AA ileal digestibility in piglets would be helpful during the formulation of diets for weaning piglets, rather than just using coefficients obtained in growing pigs. Therefore, in this study, we sought to estimate endogenous protein and AA ileal losses in piglets. Furthermore, apparent and true ileal digestibility (AID and TID) of protein and AAs from casein were measured.

Results

The average flow of protein was 20.8 g/kg of dry matter intake (DMI). Basal protein loss, as estimated by regression, was 16.9 g/kg DMI. Glutamic acid, arginine, and aspartic acid (2.2, 1.4, and 1.2 g/kg DMI, respectively) were the AAs for which greater losses were seen. The AID of protein and AAs increased as the protein level in the diet increased. A higher increment in AID was observed between diets with 80 and160 g CP/kg of feed; this finding was mainly attributable to increases in glycine and arginine (46.1% and 18%, respectively). The TID of protein was 97.8, and the TID of AAs varied from 93.9 for histidine to 100.2 for phenylalanine.

Conclusions

The basal endogenous protein loss in piglets was 16.9 g/kg DMI. Endogenous protein was rich in glutamic acid, aspartic acid, and arginine, which represented 32.7% of endogenous protein loss in weaning piglets. The TID of casein was high and varied from 93.0 for histidine to 100.2 for phenylalanine.     

秸秆还田对稻田磷素径流损失的影响

[目的]通过研究秸秆还田对稻田磷素径流损失及其对环境的影响,探索减少径流损失、提高巢湖水质的有效耕作措施。[方法]以巢湖流域稻田为研究对象,采用野外定位观测试验结合室内分析的研究方法。[结果]径流液TP含量为0.087～0.495 mg/L。PP是稻田P素随径流迁移的主要形态,约占TP的40%～70%。秸秆还田能够降低水稻生育前期径流液TP、DP和PP的浓度,减少P素径流流失风险。在当地常规耕作条件下(CT),2008和2009年稻季P素径流流失负荷分别为222.76和297.17 g/hm2,P肥表观流失率分别为0.68%和0.91%,平均为0.79%。与CT相比,秸秆还田处理(CTS)P素径流流失负荷分别减少了5.13%和18.98%,平均为12.05%。[结论]秸秆还田作为源头控制稻田磷素流失的较好措施可以在巢湖流域使用。     

旱涝交替胁迫对水稻荧光参数与光合特性的影响

为探明控制灌排条件下旱涝交替胁迫对水稻不同生育阶段荧光参数和光合特性的影响,以农田水位为调控技术指标,采用蒸渗测坑进行水稻栽培试验,在分蘖期、拔节孕穗期、抽穗开花期、乳熟期分别设置先旱后涝胁迫（HZL）、先涝后旱胁迫（LZH）2种旱涝交替胁迫模式,测定叶片相对叶绿素含量（SPAD）、主要荧光参数及光合指标的变化。结果表明,旱涝交替胁迫会减少SPAD,其中HZL处理产生的抑制作用更强;分蘖期、拔节孕穗期旱涝交替胁迫光能转化效率、光化学淬灭系数、最大潜在电子传输速率、光饱和点、净光合速率、潜在水分利用效率等荧光参数和光合指标可以恢复甚至超过对照水平,而在抽穗开花期、乳熟期产生不可逆的影响;旱涝交替胁迫下蒸腾速率、气孔导度分别在分蘖期、乳熟期受到抑制,拔节孕穗期得到促进;HZL处理提高了非光化学淬灭系数,其他主要荧光参数和光合指标HZL低于LZH处理。水稻分蘖期、拔节孕穗期LZH处理对光合作用的补偿作用更大,抽穗开花期、乳熟期HZL处理对光合作用的抑制作用较LZH处理更明显,因此,在水稻生育后期应尽量避免重度的旱涝交替胁迫,尤其要避免发生旱涝急转。