Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted Soils

Differences among open-pollinated tropical maize ( Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers.     

温度及预处理对苏丹草种子萌发的影响

本实验采用15～30℃和20～30℃2种变温,7℃、10℃、15℃和20℃4种恒温,以及0℃、5℃和10℃3种低温和硝酸钾预处理等技术,测定了苏丹草种子的萌发特性。结果表明:苏丹草种子室内最适萌发温度为20～30℃变温;预处理可破除种子休眠率达71.43～100％,并能提高幼苗的长度和简化活力指数,其中,以10℃低温预处理6天效果最好。建议苏丹草种了早春播种应以地温达15℃以上为宜。     

不同植物生长调节剂对核桃发芽和幼苗前期生长的影响

以建始核桃为试材，用不同植物生长调节剂水溶液浸泡核桃种子，研究其对核桃发芽率和幼苗前期生长速率的影响。结果表明：6-BA对核桃发芽效果最好，发芽率为44．5％，从幼苗前期生长速率考察，3-吲哚乙酸效果较好，两次测量苗高增加了14．3cm，比对照提高了37．5％。依据发芽率和生长速率两个指标综合评定，选6-BA效果最佳。     

黄菠椤根繁技术的研究

系统地叙述了黄菠椤根繁技术，黑龙江省黄菠椤根繁最佳时期为4月25日～5月15日；黄菠椤根萌芽苗的发育可分为6个阶段，即母根的新吸收根生长期，根萌芽形成期，白化径苗出土期，白化径幼苗生长期，初生根期，次生根期；促进黄菠椤根萌芽的药剂为NK7，其处理最佳浓度为200mg／L，最佳时间为20h．     

野牛草种子休眠机理初探

以野牛草为试材，在颖苞解剖结构观察以及吸胀测定的基础上进行了剥除颖苞后的０．２％ＫＮＯ３低温预处理和ＧＡ３、乙烯利两种激素前处理。前处理后在８０℃恒温和３０～１０℃变温条件下测定种子发芽率及淀粉酶活性。结果表明，野牛草种子是综合休眠型；聚合颖苞的吸水通常在置床后７２小时只能达到颖果干重的２６％，而剥去颖苞的颖果在置床后３４小时吸水量可达该种子萌发水分含量的下限即４０％；连种单位中的颖果之间没有相互抑制作用，各自的休眠与萌发是独立的。在０．２％ＫＮＯ３溶液中预冷一周，然后在１０～３０℃变温条件下萌发，其发芽率可达８５％。１５０ｍｐ／Ｌ的ＧＡ３外源激素处理可以代替ＫＮＯ３冷冻预处理。种子萌发过程中β－淀粉酶与α－淀粉酶有协同作用。     

苏式仓泡沫板吊顶隔热储粮初探

对没有隔热层的仓房，用聚苯乙烯泡沫塑料板吊顶及密封窗户，能在一定程度上降低粮温上升速度，保持粮食的新鲜度，延缓粮食的陈化，保持粮食的发芽率，节约熏蒸药剂，减轻保管员劳动强度。达到安全，经济，有效的目的。     

阿克苏地区农业资源生产潜力评价与开发分析

本文针对阿克苏地区的农业资源条件进行了分析与评价，并对光合生产潜力、光温生产潜力、光温水(气候)生产潜力及光温土生产潜力、光温水土生产潜力进行了计算。在此基础上，对提高本地区农业资源生产潜力的主要措施进行了讨论。     

地膜植棉喷灌技术研究

根据内陆干旱区的特点，为了充分发挥喷灌节水增产优势，本文提出地膜植棉喷灌技术、干播湿出及栽培配套措施。     

The influence of scale and the spatial characteristics of landscapes on land-cover mapping using remote sensing

Statistical analyses provide a means for assessing relationships between landscape spatial pattern and errors in the estimates of cover-type proportions as land-cover data are aggregated to coarser scales. Results from a multiple-linear regression model suggest that as patch sizes, variance/mean ratio, and initial proportions of cover types increase, the proportion error moves in a positive direction and is governed by the interaction of the spatial characteristics and the scale of aggregation. However, the standard linear model does not account for the different directions of scale-dependent proportion error since some classes become larger and others become smaller as the scene is aggregated. Addition of indicator variables representing class-type significantly improves the performance by allowing the model to respond differently to different classes. A regression tree model provides a much simpler fit to the complex scaling behavior through an interaction between patch size and aggregation scale. An understanding of the relationships between landscape pattern, scale, and proportion error may advance methods for correcting land-cover area estimates. Such methods could also facilitate high-resolution calibration and validation of coarse-scale remote-sensing-based land-cover mapping algorithms. Ongoing initiatives to produce global land-cover datasets from remote sensing, such as efforts within the IGBP and the EOS MODIS Land-Team, include significant emphasis on high level calibration and validation activities of this nature.