Herbicide effect on growth and seed production of Lolium multiflorum in Atlantic Canada

Lolium multiflorum Lam. (annual ryegrass) is used extensively as a forage crop and seed is produced in several areas worldwide. Seed production has been shown to be commercially possible in Atlantic Canada but improved weed control is needed. Studies were conducted in two provinces (Prince Edward Island and New Brunswick) to determine the effects of the herbicides bentazon, bromoxynil/MCPA, dicamba/MCPA, thifensulfuron/tribenuron, 2,4-D and MCPA on weed control, L. multiflorum growth, seed yields and seed germination in 1998 and 1999. The herbicides MCPA, dicamba/MCPA and bromoxynil/MCPA as evaluated in these experiments provided acceptable control of the broad-leaved weeds present and had no effect on seed yield or seed germination. Although the thifensulfuron/tribenuron caused early foliar injury, the plants recovered and it provided excellent weed control. None of the herbicides affected seed germination. MCPA, dicamba/MCPA and bromoxynil/MCPA could be used to provide control of broad-leaved weeds and thifensulfuron/tribenuron could be used if growers were willing to accept some early injury and possible yield loss to obtain the improved weed control.     

美国大豆产量生理研究的进展

从籽粒生长调控的参与因互及其机理、源库关系在产量形成中的作用、全球气候变化对大豆生育和产量的影响以及冠层（群体）光合作用等方面综述了美国大豆产量生理研究进展。     

辣子草水浸液对白菜种子萌发和幼苗生长的影响

【目的】研究辣子草对蔬菜的化感作用。【方法】以白菜为对象,研究不同浓度、不同部位的辣子草水浸液对其种子发芽率及幼苗根长和苗长的影响。[结果]随着浓度的增加,辣子草的水浸液对白菜不同部位生长的抑制作用逐渐增强;而在同一浓度下,不同部位辣子草的水浸液对白菜的影响为叶〉茎〉根。【结论】辣子草对白菜具有化感作用,且该化感物质可能主要存在于辣子草的地上部分。     

Use of a spectrum model and satellite cloud data in the simulation of wheat stripe rust (Puccinia striiformis) dispersal across the Tasman Sea in 1980

Long distance dispersal of plant pathogens has been simulated using different approaches. Models to predict dispersal of airborne spores often use simplified methods to estimate solar radiation in order to estimate mortality of spores. We incorporated a spectrum model into a Lagrangian approach to simulate dispersal of wheat stripe rust from Australia to New Zealand across the Tasman Sea. To estimate cloud cover conditions, satellite data were also used in our study. The combination of a spectrum model and satellite cloud data made it easy to identify sites at which viable spores were deposited. In our study, 0.6% of deposition near New Zealand followed exposure to UV radiation less than our mortality threshold (0.9 MJ m⁻²). Model spores of wheat stripe rust arrived at sites within 40 km from Otama, New Zealand, where wheat stripe rust was first reported in November 1980. It appeared that the uredospores were transported under an overcast cloud condition, which would increase the chance of successful infection on host crops. Further studies on the relationship between solar UV radiation and mortality of pathogen uredospores would facilitate the use of the spectrum model and satellite data to predict dispersal of airborne spores.     

Morphological characterization of seeds of three Australian wild Citrus species (Rutaceae): Citrus australasica F. Muell., C. inodora F.M. Bailey and C. garrawayi F.M. Bailey

The comparative morphology of the seeds of three Australian Citrus species, C. australasica C. inodora and C. garrawayi, was studied. Their seed characteristics were broadly similar to those of the cultivated species of the genus, when observed under light and scanning electron microscopy. Citrus garrawayi differed in seed shape (rounded to triangular) and seed coat morphology (i.e., thicker with longer epidermal protrusions) from C. australasica and C. inodora (rounded surface with flat underside in shape). The well-developed minute epidermal protrusions on the seed coat of C. garrawayi were more similar to those in the cultivated species, C. × sinensis and C. × aurantium. In contrast, the surface topography of C. australasica and C. inodora seeds was more like that of the cultivated species, C. × aurantifolia and C. × limon. Seed morphology, especially surface topography, was found to be a useful tool for taxonomic identification in Australian wild citrus.     

Effects of seed water content and storage temperature on the germination parameters of white spruce, black spruce and lodgepole pine seed

The effect of seed water content (WC) (2–3, 5–6 and 22–25%, on a fresh weight basis), storage temperature (+4, −20, −80 and −196°C) and storage duration (6, 12, 24, 48 and 60 months) on the germination of white spruce (Picea glauca (Moench) Voss), black spruce (Picea mariana (Mill.) B.S.P.) and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) seed was investigated. Germination of white spruce control (untreated) seeds and seeds adjusted to 2–3% and 5–6% WC declined after 48 months of storage at −80 and −196°C, with a further decline at 60 months at −20, −80, −196°C. Germination remained high when control white spruce seeds and seeds with 2–3, 5–6% WC were stored at +4°C, over all storage durations. Generally, black spruce and lodgepole pine exhibited high germination at all storage temperatures at 2–3% and 5–6% WC as well as the control (untreated) seed, for up to 60 months in storage. Germination declined for all three species when seed was conditioned to 22–25% WC. This loss in germination was partially recovered in white spruce seed stored at +4, −20 and −80°C after storage durations of 24, 12 and 48 months, respectively, and in black spruce seeds stored at −20 and −196°C after storage durations of 24 months. Mean germination time (MGT) was relatively constant for all species, under all conditions, except for seed conditioned to 22–25% WC, where MGT increased for white spruce seed stored 48 months at −80 and −196°C, and for black spruce seed stored 24 months at +4 and −80°C and 60 months at −196°C. These results show that the optimal storage temperatures are 4°C for white spruce, and 4, −20, −80, and −196°C for black spruce and lodgepole pine, and 2–6% water content is optimal for all 3 species at these temperatures.     

NaCl胁迫对榉树种子萌发及幼苗生理指标的影响

研究了0.1%、0.2%、0.4%、0.6%和0.8%NaCl浓度处理对榉树种子萌发和幼苗生理指标的影响.结果显示:榉树种子的发芽率,发芽指数和活力指数在较低NaCl浓度(0.1%)处理下即有显著降低;萌发后幼苗的苗高、根长在较低NaCl浓度(≤0.2%)处理下变化不显著,当NaCl浓度达到0.4%及更高对幼苗的苗高和根长显著减小;幼苗SOD、POD活性随NaCl处理浓度的增加呈先升后降的单峰曲线,MDA含量变化不明显.由此推断,榉树在种子萌发阶段对NaCl胁迫较为敏感,但萌发后的幼苗在较低NaCl浓度(0.2%)下可通过增加保护酶的活性来减少NaCl胁迫产生的危害,从而得以正常生长.     

栓皮栎种子及苗期种源变异分析

收集了栓皮栎主要分布区12个种源的种子,对种子及播种苗进行了测定分析.结果表明,栓皮栎种子的大小、质量、发芽率及苗期的生长,在种源间均存在显著差异.栓皮栎中心分布区域种源的种子相对较大,发芽率较高,来自这些区域的种源苗期生长亦较旺盛.苗期生长的显著差异表明,栓皮栎种源间及种源内优良类型选育具有很大潜力.     

稀土对白皮松育苗的效应研究

采用稀土溶液浸种处理对白皮松种子育苗的效应进行了研究,结果表明不同浓度的稀土溶液均能有效地增进白皮松种子的萌发进程,与对照相比提高白皮松种子的场圃发芽率达２５．６％￣８９．７％,出苗时间缩短６￣１１ｄ,出苗整齐,苗高年生长量增加４２．１％￣６５．７％。以１００ｍｇ／ｋｇ的稀土溶液浸种效果最好。