Conduciveness of different soilless growing media to <Emphasis Type="Italic">Pythium</Emphasis> root and crown rot of cucumber under near-commercial conditions

Substrates made from rockwool, coir dust, pumice and perlite were compared for conduciveness to Pythium root and crown rot in cucumber under near-commercial conditions. Rockwool slabs of 7 cm height were more conducive to the Pythium disease than coir dust slabs, pumice or perlite under these conditions. Temperature, oxygen concentration and water content were determined in the substrates to explain differences in conduciveness between the inorganic substrates rockwool, pumice and perlite by differences in the physical conditions. Temperature and oxygen concentration could not explain the differences but the higher disease level on rockwool was associated with a much higher water content of this substrate as compared to coir dust, pumice and perlite. Increasing the height of the substrate from 7 to 14 cm greatly decreased the percentage of diseased plants due to the Pythium disease on rockwool but had no effect on the level of disease on perlite when the substrate had been infested 4 cm below the planting hole. This difference in response in substrate height between rockwool and perlite could be explained by a much larger decrease in water content with substrate height in the rockwool than in the perlite substrate. Temperature in the substrates were above 30 °C for more than 6 h on sunny days in June and reached maximum values of 35 °C or more. These temperatures are highly favourable for the pathogen P. aphanidermatum but will have adverse effects on most biocontrol strains.     

铁营养对水培芥菜和生菜生长及根系一些酶类特性的影响

本研究通过调节水培营养液中铁深度分别为０，２．８，５．６，８．４，１１．２和１４．０ｍｇＦｅ／Ｌ的６个水平种植生菜和芥菜，比较这两种蔬菜在不同的铁浓度下生长及其对植物铁含量以及根系过氧化氢酶和过氧化物酶活性的影响。结果表明，生菜和芥菜分别在２．８和５．６ｍｇＦｅ／Ｌ时产量最高。在此最适水平以下，随铁深度的增高，产量随铁浓度的增高，产量随着提高；但铁深度超过辽个水平，生菜表现出毒症状，产量降低，芥菜     

水培甘薯的光合研究

使用LI-6400便携式光合测定系统对三种水培甘薯食用型南薯88、兼用型徐薯18和特用型南紫薯008的光合进行了测定,利用非直角双曲线模型对三种甘薯品种的光合作用生理参数进行拟合。结果表明,不同类型甘薯品种的光响应曲线的特征参数存在着差异,食用品种南薯88的光和潜力最强,可在高密度栽培下发挥群体优势达到高产;兼用型品种徐薯18对光的适应性次之,在较高密度栽培下能发挥群体优势;特用型品种南紫薯008的光合潜力和对光的适应性均最弱,但对弱光的利用率最高,最适合于间套作。不同类型甘薯品种间的生理指标存在相似的变化,气孔导度和蒸腾速率对净光合速率的影响达极显著正相关,胞间CO2浓度对甘薯净光合速率的影响呈极显著负相关,揭示了不同类型甘薯品种在光能利用上的差异。南紫薯008在较低光强下能很快使气孔打开,蒸腾速率也快速增加,从而使光合速率也加强。在高光强下,南薯88的气孔导度、胞间CO2浓度值最大,这可能是南薯88光合速率高的原因。为田间甘薯的共性和特异性研究提供了一定的理论基础。     

香蕉枯萎病苗期抗性鉴定的水培接种法研究

[目的]探索利用水培法接种进行香蕉枯萎病苗期抗性鉴定的可行性,为香蕉苗期接种技术的改良及香蕉枯萎病抗性种质材料快速筛选提供科学依据.[方法]利用水培接种的方法对比巴西、农科1号、抗枯5号3个不同抗性香蕉品种的枯萎病发病率及平均病情指数间的差异,并与3个香蕉品种的田间病害评价结果进行比较,同时利用K2平板计数法研究香蕉枯萎病菌4号生理小种(Foc4)在水培营养液中的生长动态.[结果]3个已知抗性的香蕉品种通过水培接种法鉴定的结果与抗感品种本身的抗病性程度相吻合,抗感品种的发病率和病情指数差异明显,在接种后第9d即能明显区分.香蕉枯萎病菌在水培营养液中浓度基本恒定,保持在105～106 CFU/mL,水培环境能为病原菌侵染寄主提供稳定的营养条件.[结论]水培接种方法能够快速、准确地区分香蕉品种对枯萎病的抗性,在香蕉抗性种质材料的快速鉴定及筛选中推广应用潜力大.     

热带地区夏季水培小白菜营养液浓度的研究

为了研究热带地区夏季(4月至6月)水培小白菜适宜的营养液浓度,进行了2个试验。①研究了定植后营养液的5个不同浓度处理(华南农业大学叶菜B配方的1/4倍、1/2倍、3/4倍、1倍和5/4倍浓度)对水培小白菜生长和品质的影响。结果表明,3/4倍的营养液浓度处理下的小白菜单株产量为11.88 g,硝态氮含量为1 792.25 mg/kg,维生素C的含量为0.037 mg/g,综合指标在各处理中表现最优。②研究了收获前7 d营养液不同浓度处理〔华南农业大学叶菜B配方的1/4倍、1/2倍、3/4倍、1倍和清水(CK)〕对水培小白菜生长和品质的影响。结果表明,收获前7 d用1/4倍营养液浓度处理下的小白菜单株产量为16.20 g/株,硝态氮含量为1 300.79 mg/kg,维生素C的含量为0.035 mg/g,综合指标在各浓度处理中表现最优。在热带地区夏季,用华南农业大学叶菜B配方进行小白菜水培时,可在定植后前期用3/4倍的营养液浓度进行培养,收获前1周换用1/4倍浓度的营养液进行培养最为经济有效。     

不同浓度营养液对樱桃番茄生长发育的影响

以3种浓度的营养液,采用水培、基质培对樱桃番茄进行栽培试验。结果表明:樱桃番茄株高、茎粗、叶面积、叶数、叶绿素含量等,水培均好于基质培。采用水培方式栽培选用1.5倍剂量浓度的营养液,其生长发育优于0.5倍和1.0剂量营养液;采用基质培方式选用1.0剂量浓度的营养液,其生长发育优于0.5倍和1.5倍剂量营养液。     

不同营养液配方对工业大麻幼苗生长的影响

工业大麻作为一种重要的经济作物在世界上被广泛种植,在纺织、油用、建材、保健和医药方面具有较高的利用价值.水培工厂化生产是工业大麻产业发展的一个趋势,但关于适合工业大麻生长的专用水培营养液配方及浓度尚未报道.为获得适合工业大麻生长的专用水培营养液配方,利用标准霍格兰营养液(1 H)和根据工业大麻需肥规律自主设计的不同浓度...     

水培法磷矿石对小麦生长的影响

Screening cultivars to grow under conditions of low phosphorus (P) availability and utilize P efficiently from compounds of low solubility in soils may be beneficial to overcome poor plant growth in P-deficient soils.The growth behavior and P utilization efficiency of seven wheat cultivars grown in hydroponics were studied,using rock phosphate as P source.The wheat cultivars grown for 30 days were significantly different in biomass accumulation,P uptake and P utilization efficiency.The dry matter production of all the cultivars was significantly correlated with P uptake,which in turn correlated to the drop in the root medium pH.The ranking of wheat cultivars on the basis of dry matter yield,P uptake and P utilization efficiency was Zamindar 80 ＞ Yccora ＞ C 271 ＞ WL 711 ＞ Barani 83 ＞ PARI 73 ＞ Rohtas.The cultivar Zamindar 80 appeared to possess the best growth potential in P-deficient soils.     

Availability of soil boron fractions to M.26 apple rootstock

The availability of various boron (B) fractions in soil to M.26 apple (Malus spp.) rootstock was examined. The study was carried out in a greenhouse on soils with diverse chemical and physical properties. The following B fractions were determined: (i) B in soil solution, (ii) B non‐specifically adsorbed on soil surface, (iii) B specifically adsorbed on soil colloid surfaces, (iv) B occluded in Mn oxyhydroxides, (v) B occluded in noncrystalline aluminum (Al) and iron (Fe) oxides, (vi) B occluded in crystalline Al and Fe oxides, (vii) B fixed with soil silicates, and (viii) total soil B. In the studied soils there were: 0.07–0.17 mg kg^‐1 B in soil solution, 0.01–0.03 mg kg^‐1 B non‐specifically adsorbed on soil surface, 0.04–0.08 mg kg^‐1 B specifically adsorbed on soil colloid surfaces, 0.28–0.67 mg kg^‐1 B occluded in manganese (Mn) oxides, 4.03–17.22 mg kg^‐1 B occluded in noncrystalline Al and Fe oxides, 8.93–50.62 mg kg^‐1 B occluded in crystalline Al and Fe oxides, 12.2–42.5 mg kg^‐1 B fixed with soil silicate, and 52.9–82.2 mg kg^‐1 total B. Simple correlation analysis showed positive correlation between B contents in M.26 apple rootstocks and amounts of B in soil solution (r=0.77), B non‐specifically adsorbed on soil colloid surfaces (r=0.65), B specifically adsorbed on soil surface (r=0.76) and B occluded in Mn oxyhydroxides (r=0.77). No relation was found between plant B contents and amounts of B occluded in non‐crystalline and crystalline Al and Fe oxides, B fixed with soil silicates and total B. The results indicated that extraction of B by 0.1 M NH₂OH HCl solution adequately represented amounts of B in soil solution, B non‐specifically and specifically adsorbed on soil compound surfaces and B occluded in Mn oxyhydroxides to assess availability of B to apple trees.     

Effects of Cadmium and Lead on Plant Growth and Content of Heavy Metals in Arugula Cultivated in Nutritive Solution

A greenhouse assay using an arugula (Eruca sativa L.) hydroponics system was carried out to evaluate the following effects of increasing amounts of cadmium and lead in nutritive solution: (a) production; (b) translocation of cadmium (Cd) and lead (Pb) throughout the plants; (c) possible interactions of Cd and Pb with other mineral elements, transition metals, essential to plants; (d) tolerance limits to Cd and Pb with regard to production; and (e) chelating interaction of Cd and Pb with root substances. The absorption of Cd and Pb increased with increasing dosages in solution. Roots accumulated larger amounts of metals than shoots. Plants develop better with less than 0.025 mg L^?1 of Cd, with a damaging Cd concentration of 1 mg L^?1. The tolerable Pb concentration was up to 10 mg L^?1. Cadmium and Pb translocate poorly in plants and their deleterious effect is due to the deposit of very stable chelates in roots.