赤峰市松山区土地利用动态变化及其原因分析

以TM遥感资料为信息源 ,利用 3S技术手段 ,对内蒙古自治区赤峰市松山区 1987,1993,2 0 0 0年的土地利用变化进行了分析。结果表明 ,在不同年度内 ,其主要的土地利用类型为耕地、草地和林地。土地利用类型的总量变化也以这 3种土地利用类型和建设用地变化最大。而从年变化速率看 ,1987- 2 0 0 0年 ,以建设用地的增加和未利用土地类型的减少最为快速。从土地利用类型转化的方向看 ,以耕地、草地和林地相互之间的转化最为频繁。从土地利用类型的空间稳定性看 ,耕地的稳定性最高 ,其次为草地 ;而最不稳定的土地利用类型为未利用土地。利用相关分析所作的土地利用变化动因显示 ,该地区土地利用变化的驱动因素主要是社会与经济因素 ,其中以总人口、农业总产值、粮食作物产量总计、农牧民人均纯收入、化肥使用面积和化肥实物量等因子的作用最大 ,而自然因素对该地区土地利用变化的影响极小。     

Germination ecology of seeds of the annual weeds Capsella bursa-pastoris and Descurainia sophia originating from high northern latitudes

Low temperatures may inhibit dormancy break in seeds of winter annuals, therefore it was hypothesized that seeds of Capsella bursa‐pastoris and Descurainia sophia that mature at high latitudes in late summer–early autumn would not germinate until they had been exposed to high summer temperatures. Consequently, germination would be delayed until the second autumn. Most freshly matured seeds of both species collected in August and September in southern Sweden were dormant. After 3 weeks of burial at simulated August (20/10°C) and September (15/6°C) temperatures, 28 and 27%, respectively, of the C. bursa‐pastoris and 56 and 59%, respectively, of the D. sophia seeds germinated in light at 15/6°C. In contrast, in germination phenology studies conducted in Sweden, only a few seeds of either species germinated during the first autumn following dispersal. However, there was a peak of germination of both species the following spring, demonstrating that dormancy was lost during exposure to the low habitat temperatures between late summer and early autumn and spring. Nearly 100% of the seeds of both species subjected to simulated annual seasonal temperature changes were viable after 30.5 months of burial. In the burial study, exhumed seeds of C. bursa‐pastoris were capable of germinating to 98–100% in light at the simulated spring–autumn temperature regime (15/6°C) in both spring and autumn, while those of D. sophia did so only in autumn. In early spring, however, seeds of D. sophia germinated to 17–50% at 15/6°C. Thus, most seeds of these two annual weeds that mature in late summer do not germinate in the first autumn, but they may do so the following spring or in some subsequent autumn or spring.     

Anoda cristata control with glyphosate in narrow- and wide-row soyabean

Experiments evaluated the effect of glyphosate rate and Anoda cristata density, on crop and weed biomass and weed seed production in wide (70 cm) and narrow rows (35 cm) glyphosate‐resistant soyabean (Glycine max). Soyabean density was higher at 35 cm row spacing as an increase in planting rate in narrow‐row soyabean is recommended for producers in Argentina. Soyabean biomass at growth stage V4 (four nodes on the main stem with fully developed leaves beginning with the unifoliate leaves) was higher when grown on narrow than in wide‐rows but was not affected by the presence of A. cristata. At growth stage R5 (seed initiation – seed 3 mm long in a pod at one of the four uppermost nodes on the main stem, with a fully developed leaf and full canopy development), crop biomass was greater in narrow rows compared with wide rows with 12 plants m^?2 of A. cristata. In narrow‐row soyabean, a single application of a reduced rate of glyphosate maintained soyabean biomass at R5 and provided excellent weed control regardless of weed density. In wide‐row soyabean control was reduced at the high weed density. Regardless of row spacing, A. cristata biomass and seed production were severely reduced by half of the recommended dose rate of glyphosate but the relationship between biomass and seed production was not altered. Glyphosate rates as low as 67.5 g a.e. ha^?1 in narrow rows or 540 g a.e. ha^?1 in wide rows provided excellent control of A. cristata. To minimize glyphosate use, planting narrow‐row soyabean are effective where A. cristata density is low.     

Spatial distribution of Lolium rigidum seedlings following seed dispersal by combine harvesters

This paper considers the relationships between the dispersal of seeds and the distribution pattern of an annual weed. A comparative study of seed dispersal by combine harvesters, with and without a straw chopper attached, was established using Lolium rigidum, a common weed in Mediterranean cereal crops. Seed dispersal distance was quantified and the relationships between dispersal and fine‐scale seedling distribution evaluated. Primary dispersal of L. rigidum seeds occurs in a very limited space around the parent plants, but the density of seed is low because most seeds do not fall from spikes spontaneously. In contrast, many seeds are spread by combine harvesters. In this study the maximum dispersal exceeded 18 m from established stands in cereal fields, although the modal distance was close to the origin. In addition, the action of the combine harvesters tended to accumulate L. rigidum seeds predominantly under the straw swath, with some lateral movement. This action could explain the fine‐scale banded pattern of L. rigidum in cereal fields. Although the treatment of straw by the standard and straw chopper combines differed, the resultant seed distribution showed few differences.     

Aerial seed germination and morphological characteristics of juvenile seedlings in Commelina benghalensis L.

Seed germination, seedling emergence, and the morphological characteristics of juvenile seedlings of Commelina benghalensis L. were observed. For aerial seeds collected in September and October, seedling emergence peaked in April and June for large seeds and from June to August for small seeds, whereas seedling emergence for large seeds collected in November showed peaks in March and April under natural rainfall conditions, and in April and June under irrigation conditions. Seedlings from small seeds emerged intermittently over a longer period from April to August under both conditions. Aerial seeds of C. benghalensis germinated on wet filter paper on the second day after seeding (DAS) for large seeds and the fourth DAS for small seeds. The germination percentage for large seeds was higher than that for small seeds by the 14th DAS. The germination percentage for large aerial seeds showed no significant difference between light and dark conditions. However, the percentage for small aerial seeds was higher under light than under dark conditions. Seedlings from large aerial seeds emerged on the third DAS at 0–50 mm soil depths. The percentage of emergence at 0 and 1 mm soil depths increased until the 30th DAS, whereas those at soil depths of 5–50 mm showed no change after the 9th DAS. There was no emergence at a soil depth of 100 mm. Seedlings from small aerial seeds emerged on the 6th DAS at 0–1 mm soil depths, with the percentage increasing until the 30th DAS. Although seedlings at 5 and 10 mm soil depths also emerged on the 6th DAS, there was no change in the percentage after the 12th DAS. There was no emergence at soil depths of 20–100 mm. The hypocotyl and taenia (part of the cotyledon connected to the seed) in juvenile seedlings that emerged from soil depths of 50 mm were longer than those in seedlings emerging from a soil depth of 1 mm.     

华北农牧交错带退化草地土壤种子库动态变化

对华北农牧交错带不同退化演替阶段土壤种子库的数量和物种组成及与地上植被的关系进行了初步的研究,结果表明:农牧交错带草地在刈割和放牧等干扰下,发生逆行演替,土壤种子库中植物种类及种子数量呈递减的趋势,轻度退化类型土壤种子库物种组成最高,有23种植物,种子数量最多,有4 303粒,禾本科所占比例较大,为32.3%;而极度退化草地物种组成最低,有14种植物,种子数量仅有1 156粒,禾本科只占8.4%.草地逆行演替过程中植被与土壤种子库在物种组成上存在一定差别,中度退化阶段差别最大,有18种植物未在种子库中出现,极度退化阶段差别最小,有2种未在种子库中出现.     

植物育种的物理学方法

介绍了草原生态恢复中选育优良牧草种子的一些物理学方法,包括电场、磁场、物理辐射、激光、离子束和交变应力等在植物的生物学效应、诱变育种和转基因技术中的应用.     

四川省2种生境条件下黑麦草种子生产性能的研究

对四川省的丘陵区(洪雅)和中山地区(汉源)2种生境条件下的黑麦草种子生产性能进行了研究分析,结果表明,试验两地的种子产量和质量均有显著差异.其中,洪雅点种子产量为244.0 kg/hm2,汉源点的种子产量为532.8 kg/hm2.两样地的种子质量相比,汉源点的发芽势、发芽率、四唑染色数和四唑脱氢酶均高于洪雅点.两地的种子产量与其构成因素的相关性基本一致,均呈显著相关;相关性强弱依次为:每生殖枝种子数>生殖枝数>每生殖枝小花数>分蘖数>每生殖枝小穗数>千粒重.每生殖枝种子数对种子产量贡献最大.     

羊草种子萌发相关基因的筛选及表达分析

前期实验表明,变温处理(28 ℃ 12 h/16 ℃ 12 h)可显著提高羊草种子的萌发率,且羊草种子萌发中的第1天是接受变温信号的关键时期。以此为研究基础,结合羊草种子变温萌发的转录组测序数据,针对羊草种子萌发初期对变温处理的响应筛选出与种子萌发、休眠及低温相关的基因24个,利用测序结果中这些基因的RPKM值制作基因表达热图并分析其表达差异。以萌发率高、低的两种羊草种质的种子为材料,对24个基因在恒温12 h(28 ℃)和变温1 d(28 ℃ 12 h/16 ℃ 12 h)萌发处理中的表达分别进行了定量分析。结果表明,与恒温对照相比,变温处理12 h后,表达明显上调的基因有SAIN1,PP2C62,EXPB3,EXPB4,GA3ox,EXPA2和EXPA7,而表达明显下调的基因有bHLH49,GID1,ABI8,Chi1,11833,CBF3,NAC2,PP2C72,SAIN2和5423。通过进一步分析相关基因在高、低萌发率两个种质中表达的差异,筛选出其中可能与羊草种子萌发相关的基因有几丁质酶基因Chi1,转录因子基因CBF3,羊草新基因5423,赤霉素合成基因GA3ox,细胞松弛素蛋白基因EXPB4和羊草新基因SAIN1,将为下一步阐明羊草种子萌发的分子作用机理奠定基础。     

黄土高原人工灌草系统不同立地条件土壤种子库特征

本研究通过野外调查取样与室内试验相结合，连续两年对黄土高原人工灌草系统不同坡向、坡位进行取样，以期对该区土壤种子库的物种组成、密度特征及其物种多样性进行初步了解。研究结果表明：该人工灌草生态系统土壤种子库共有9科，15种，其组成因坡位、坡向以及年份而异；坡向、坡位均显著影响土壤种子库物种多样性指数、丰富度指数与土壤种子库密度（P<0.05），土壤种子库密度为3 218～5 492粒·m^-2，总体呈现为阴坡显著高于阳坡（P<0.05），下坡位显著高于上坡位（P<0.05）；坡位和坡向均对物种均匀性系数无显著影响；年份对土壤种子库无显著影响。上述研究可为黄土高原人工灌草系统的可持续利用与恢复提供参考依据。