Variation in temperature requirements for germination and early seedling root development in Chamaecrista rotundifolia and three allied species

Two experiments are discussed. In the first, rates of root elongation during the first four days of growth at 25 °C were studied in Chamaecrista rotundifolia (34 accessions), C. nictitans (2 accessions), C. pilosa (1 accession) and C. serpens (3 accessions). In the second, a comparison was made of germination characteristics of 14 accessions of C. rotundifolia and one of C. pilosa at nine constant temperatures (11–27 °C). Entries included accessions from a wide latitudinal range. There were statistically significant differences in root length on all four days of measurement. No accession had significantly longer roots than the commercial cultivar cv. Wynn on day 1, but over the following three days, 4, 10 and 13 accessions had significantly longer roots, respectively. Root length on day 4 was positively correlated with latitude of origin. In the second experiment, maximum germination occurred at 25.5–27 °C, with progressively lower percentages at lower temperatures. There were highly significant differences between accessions at each temperature (P<0.001), and a highly significant accession × temperature interaction. No accession had a higher germination percentage than cv. Wynn at any temperature. Percentage mortality differed significantly (P<0.05) at all temperatures except 27 °C. Mortality at low temperature was negatively correlated with latitude of provenance. Increased temperatures up to 22.5 °C reduced the time taken to reach 50% of maximum germination (T₅₀), and thereafter it was reasonably constant. With one exception (22.5 °C), no accession germinated significantly more quickly than cv. Wynn, and at 13 °C cv. Wynn germinated significantly more rapidly than all other entries. Over all temperatures, there was a significant negative correlation between days to 50% germination and latitude of provenance. Estimated base temperature for germination (T _b ) ranged from 10.6 °C to 13.6 °C. T _b was positively correlated with latitude of provenance. It is argued that accessions from higher latitudes have developed mechanisms for survival of soft seed at low temperatures, low base germination temperature, germination rates and root elongation rates that adapt them to an environment with summer-dominant rainfall and winters which are too cool to support growth.     

木质部溶质分析法测量豆科植物的生物固氮

固氮植物与未长根瘤的豆科植物所同化氮素的运输形式有所不同,许多豆科植物所固定氮素是以酰脲或酰胺的形式在木质部中运输的。测定一些豆科植物木质部液汁中酰脲的相对含量,则可以估测出该植物的固氮能力。该法县有取样方便、测量简单,对某些植物可以做到非破坏性测量等优点。     

Amelioration of a degraded Oxic Paleustalf by leguminous and natural fallows

Abstract. The restorative ability of herbaceous ( Psophocarpus palustris, Pueraria phaseoloides ) and woody ( Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis ) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis , test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.     

甘肃省白龙江流域豆科植物根瘤菌共生固氮研究

对甘肃省白龙江流域甘南、陇南的大部分地区豆科植物——根瘤菌资源进行了调查 ,共采集 2 1属45种豆科植物 6 9份根瘤样品。从 6 9份样品中获 6 3株根瘤菌 ,对其中 44株根瘤以 13种寄主进行了回接试验 ,31株结瘤 ,结瘤率 70 .5 %。该区根瘤一般带有粉红色 ,形态比较规则。乙炔还原活力测定结果表明 ,88.5 %为有效根瘤。不同种根瘤固氮活性相差不大 ,但高于甘肃省其它地区。对豆科植物在蓄水保土 ,改良土壤状况中的地位进行了讨论。     

Research achievements in plant resistance to insect pests of cool season food legumes

Plant resistance to at least 17 field and storage insect pests of cool season food legumes has been identified. For the most part, this resistance was located in the primary gene pools of grain legumes via conventional laboratory, greenhouse, and field screening methods. The use of analytical techniques (i.e., capillary gas chromatography) to characterize plant chemicals that mediate the host selection behavior of pest insects offers promise as a new, more rapid way to differentiate between insect-resistant and susceptible plant material. Examples of research achievements in mechanisms of resistance and host-plant resistance within the context of integrated control programs are discussed. Accelerating the development and subsequent releases of insect-resistant cultivars to pulse farmers requires more involvement from interdisciplinary teams of plant breeders, entomologists, plant pathologists, plant chemists, molecular biologists, and other scientists.     

Climatic adaptation in subterranean clover populations

Summary Long-term persistence and, hence, agronomic success as a pasture of the annual species subterranean clover depend primarily on seed yield and seed survival over seasons. In natural populations, plant characteristics influencing seed setting and formation of seed reserves in the soil are expected to be adjusted to the prevailing environmental conditions of the sites of origin. Knowledge on plant/environment relationships may provide information on adaptive strategies of persistence, and guidelines for selecting adapted varieties to specific conditions. On pure lines from a number of populations such relationships were assessed for flowering time, seed yield, burr fertility, individual seed weight, initial hardseededness, and rate of hardseededness breakdown over summer. Flowering time decreased on decreasing annual rainfall, i.e., on shortening the growing season, as adaptive response to the need of producing adequate seed before the onset of the dry season. Individual seed weight decreased on decreasing rainfall, and increasing temperatures. Hard-seed maintenance over summer was higher in populations from hot and dry environments, where the marked effect of temperature on hardseededness breakdown exerts a strong selective pressure. Within-population variation, assessed on flowering time, was particularly wide, with early genotypes occurring even in populations from long-season environments. The adaptive relevance of maintaining high levels of within-population polymorphism to cope with unpredictable climatic fluctuations is discussed. Number of constituent lines as a measure of the population structure, and intra-population variation were both influenced by altitude and rainfall, tending to decrease as the climatic selective pressure becomes severe, under both low-rainfall, hot conditions and high-elevation, cold-prone environments.     

杂豆植物化学素研究进展

杂豆富含植物化学素,这些天然化学物质具有一定的生物活性,尤其在预防与营养相关的慢性疾病方面。现对多种杂豆的植物化学素进行综述,包括植物化学素的种类及其抗氧化、预防代谢综合症和预防癌症的效果等,旨在为杂豆的合理开发利用提供科学依据。     

Aspects of the productivity of forage legumes in Northern Europe

A database on the productivity of red clover (Trifolium pratense), white clover (Trifolium repens), lucerne (Medicago sativa), lotus (Lotus corniculatus) and galega (Galega orientalis) was compiled. It contains 1852 observations for 330 trials at fifty‐three sites in eight north European countries for the period from 1977 to 1997. The database includes information on climatic and site characteristics, as well as agronomic data, collated into four smaller data sets. This has permitted four key agronomic issues to be examined, namely: (i) how yield for a given variety varies under different environmental conditions; (ii) how the relative performance of different species varies between sites; (iii) how persistence varies between species and sites; and (iv) what the nature of the relationship is between varieties, yield and sites within a species? Cluster analysis revealed that geographical location had a fairly strong influence on yield. Across sites for an individual variety, the cumulative day‐degrees during the regrowth period had the highest correlation with total yield. In terms of the relative performance of different forage legume species across sites, red clover and lucerne were estimated to yield about 2·5 t DM ha^?1 more than white clover and there was a significant impact of cumulative day‐degrees during regrowth and the age of ley on the total yield. It was found that red clover had the lowest persistence index and lucerne the highest. As regards the interaction between yield, varieties and sites, the length of growth period and the age of the ley explained two‐thirds of the variation in total yield in red clover varieties of contrasting maturity types.