The roles of light and pericarp on seed dormancy and germination in feral Raphanus sativus (Brassicaceae)

The timing of seed germination may determine the success of a weed species in an agroecosystem, and its expression is modulated by environmental conditions, but also by seed physiology and anatomy. The aims of this study were to investigate the roles of light, pericarp, dry storage and cold stratification on seed dormancy and germination in feral radish, a troublesome agricultural weed in temperate zones of the Americas that reduces crop yields. To this end, we used isolated intact pods and extracted seeds to test germination over time under contrasting temperature, light and storage conditions. Here, we showed that fresh seeds were non‐dormant, but that light and the presence of the pericarp reduced germination, especially under low temperatures. The pericarp reduced the final water content absorbed by seeds inside pods and decreased absorption/dehydration rates. The pericarp showed several small lignified cell layers in the endocarp, and x‐ray images displayed the lack of space between the partially embedded seed and the endocarp. Dry storage and cold stratification were ineffective in breaking the dormancy imposed by the pericarp. The apparent requirement for darkness and the mechanical restriction of the pericarp may have the potential to induce dormancy, spreading the timing of seed germination over a more extended period and hindering the control of feral radish.     

赤霉素及机械处理的相互作用对破除Sandersonia aurantiaca种子休眠的研究

在预备试验的基础上，选用了21种促进种子发芽的方法，结果显示，完整的s．aurantiaca种子对任何处理都无响应，砂纸磨擦 近胚根处切除小部分可使种子发芽率提高至11％。以上处理结合300mg／L GA3溶液的使用可破除种子休眠，使种子发芽率提高到69％以上。结果还表明，S．aurantiaca种子发芽的适宜温度为20℃；25℃ 16h／d光照及30℃的条件可降低种子的发芽率。研究还对S．aurantiaca种子的吸胀能力以及所含抑制物对生菜种子发芽的影响进行了比较。初步得出，S．aurantiaca种子具有种皮限制和种胚休眠的双重休眠机制，GA3和机械处理的相互作用可破除种子休眠。     

PEG对10℃低温吸胀下实葶葱种子萌发的影响

基于种子萌发试验,测定了10℃低温对实葶葱种子发芽的影响及浓度为0%、10%、15%、20%、25%、30%的PEG处理对实葶葱种子低温吸胀1、2、3、5、7 d的缓解作用.结果表明:10℃低温吸胀持续时间超过临界时间(1 d)时就会抑制实葶葱种子的萌发.10℃低温吸胀通过PEG的渗透调节,可显著改善实葶葱种子的萌发,其中以处理浓度15%时效果最好,并随着低温吸胀时间的延长PEG的作用越明显.各浓度PEG处理10℃低温吸胀的实葶葱种子1d时种子萌发效果最佳.     

Seedborne Fusarium on Douglas-fir: Pathogenicity and seed stratification method to decrease Fusarium contamination

Twelve Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlots from coastal British Columbia were assayed for seedborne Fusarium. All of the seedlots were contaminated with Fusarium. Percent of nonstratified seeds from individual seedlots harboring Fusarium ranged from 0.3% to 95.4%. Sixty-seven percent of the seedlots had Fusarium on less than 2% of the seeds. Post-stratification seedborne Fusarium levels were significantly less for running water imbibition compared to standing water imbibition. However, seedling growth at a container nursery was not consistently different for stratified seed imbibed initially in standing or running water. Fusarium disease symptoms were not observed in the nursery environment. The species of Fusarium isolated from seed were F. acuminatum, F. avenaceum, F. lateritium, F. moniliforme, F. oxysporum, F. poae and F. sambucinum. Twelve Fusarium isolates, comprising six species, were assessed for pathogenicity. Disease symptoms were observed after four weeks incubation and Fusarium isolates ranged in virulence from low to high. Fusarium oxysporum isolates were the most pathogenic.     

基于水平吸渗确定土壤水分扩散率的解析-修正法

准确测试土壤水分扩散率是研究水分在土壤中运移的关键之一.针对水平吸渗法测试土壤水分扩散率易受边界效应影响的问题,该研究构建解析-修正法,以提高测试结果的精度.假设第一类边界条件下,一维水平入渗Richards方程解的形式与其对应线性化方程的解析解相似,结合常数变易法,推导了一维水平入渗Richards方程的近似解析解....     

不破坏种子活力测定方法研究Ⅱ种子活力与呼吸速率的关系

对不同活力的白菜种子进行连续5次吸水回干处理,发现吸水回干处理使种子的抗劣变能力显著提高。测定种子吸胀初期的呼吸速率发现：高活力种子（发芽率82％）和中等活力种子（发芽率68％）的呼吸速率显著高于低活力种子（发芽率44％）的呼吸速率,但高活力种子与中等活力种子的呼吸速率差别不明显。种子经吸水回干处理（1～5次）再自然老化后,种子吸胀初期的呼吸速率则与种子活力呈明显的正相关。     

残膜对土壤水分渗吸过程中湿润锋的影响

采用室内水分渗吸试验,通过设置6个残膜面积水平,分别为0.25,0.50,1.00,2.00,4.00,8.00 cm2,和4个残膜密度水平,分别为60,180,300,420 kg/hm2,以无膜作对照,共25组试验处理,分析了不同残膜密度及尺寸对湿润锋的运移的影响.分析结果显示,在容重为1.53 g/cm3的黏壤土...     

Uptake of Triticonazole,during Imbibition,by Wheat Caryopses after Seed Treatment

The uptake of ¹⁴C-labelled triticonazole by wheat caryopses during imbibition was investigated. The uptake from an aqueous solution appeared to be driven by mass flow rather than by accumulation in seed lipids. During treatment with a liquid seed-dressing preparation of triticonazole, c. 1 μg triticonazole per caryopsis (2·4% of applied triticonazole) entered the seed. During germination in soil, another c. 1 μg triticonazole per caryopsis entered the seed in 24 h. In killed seeds, no penetration was observed between 24 h and 72 h after the beginning of imbibition. After seed treatment and imbibition in soil, triticonazole appeared to be located in the seed coats and embryo, but not in endosperm; experiments suggested that the testa acted as a barrier. Under our conditions, the pathway from seed coats to shoots was not an important route for triticonazole uptake by the shoots. © 1997 SCI.     

液氮处理对刺槐和胡枝子种子硬实的影响

研究了液氮不同处理时间(0.1、0.5、5h)对刺槐和胡枝子种子硬实的影响。结果表明:液氮处理能有效地打破刺槐种子硬实,并促进吸胀和萌发;对胡枝子没有明显效果,且硬粒破除效果与浸入液氮时间无关。液氮处理后2物种种子均能正常萌发。该结果为刺槐种子播种前打破硬粒提供了技术支持。