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.     

岩棉作为草坪草育苗基质的坪床性能初探

对岩棉作为草坪草生长基质的可能性进行了初步研究,发现草坪草在岩棉上能够生长良好,较低密度的岩棉更为合适;应用岩棉田问建植草坪应解决好种子、岩棉、土壤三者相互固定的问题;岩棉本身并不具有很强的保水性能,但作为播种覆盖材料时,由于它是横向纤维压制而成,切断了土壤毛管作用,减少水分蒸发,表现出非常强的节水作用。     

Control of Fusarium wilt in carnation grown on rockwool by Pseudomonas sp. strain WCS417r and by Fe-EDDHA

In carnations grown on rockwool disease incidence of fusarium wilt caused byFusarium oxysporum f.sp.dianthi (Fod) was reduced when Fe-EDDHA instead of Fe-DTPA was used as iron source in the nutrient solution. Addition ofPseudomonas sp. strain WSC417r intensified this reduction in the cultivar Pallas, moderately resistant to Fusarium, but not in the susceptible cultivar Lena. Treatment of plants with Fe-EDDHA instead of Fe-DTPA as iron source resulted in higher numbers and percentages on the roots, ofin vitro antagonistic fluorescent pseudomonads. However, differences were only significant at 56 days after planting for cv. Lena and at 14 and 28 days after planting for cv. Palas. Both chelators, at different concentrations, had no effect on root colonization by eitherPseudomonas sp. strain WCS417r orFod strain WCS816. However, when coinoculated, reduced numbers of propagules ofFusarium were found at concentrations of Fe-EDDHA lower than 10^–5 M.Higher concentrations of the siderophore fusarine produced byFod strain WCS816 were demonstrated when Fe-EDDHA instead of Fe-DTPA was used as iron source in culture media. At equal concentrations, no such differences were found in the amount of siderophore produced by WCS417r. Germ tube length ofFod was less with Fe-EDDHA than with Fe-DTPA. The reduction of germ tube length was stronger when the purified siderophore of WCS417r was added in excess to the culture media with Fe-EDDHA than those with Fe-DTPA. Therefore, the observed reduction of germ tube growth can not completely be explained by iron deprivation. It appeared that EDDHA exhibited a toxic effect for conidia ofFod strain WCS816 as well.we conclude that the observed disease reduction by Fe-EDDHA is a consequence of a limitation of iron availability forFod. This limitation is possibly intensified by the increase in number or percentage of antagonistic fluorescent pseudomonads that strongly compete for iron. The additional effect after bacterization withPseudomonas strain WCS417r in Fe-EDDHA treated carnations of cv. Pallas is likely to be due, at least partly, to a direct competition for iron between the siderophores ofFod strain WCS816 and ofPesudomonas sp. strain WCS417r.Samenvatting Verwelkingsziekte in anjers op steenwol, veroorzaakt doorFusarium oxysporum f. sp.dianthi (Fod), werd gereduceerd indien het ijzer-chelaat Fe-EDDHA in plaats van Fe-DTPA werd toegevoegd aan de nutriëntenvloeistof. Bacterisatie metPseudomonas sp. stam WCS417r had een additioneel effect bij de matig resistence cultivar Pallas maar niet bij de vatbare cultivar Lena. Toevoeging van Fe-EDDHA in plaats van Fe-DTPA aan planten als ijzerbron resulteerde op de wortels in hogere aantallen en percentages fluorescerende pseudomonaden, diein vitro antagonistisch waren ten opzichte vanFod. De verschillen waren echter alleen significant 56 dagen na planten voor de cultivar Lena en 14 en 28 dagen na planten voor de cultivar Pallas. Beide chelaten vertoonden bij verschillende concentraties geen effect op de kolonisatie van de wortel door beide microorganismen. Echter, wanneer beide micro-organismen gezamelijk werden toegevoegd nam de wortelkolonisatie doorFod stam WCS816 af bij concentraties lager dan 10^–5 M Fe-EDDHA. Er werd meer van het siderofoor fusarine doorFod stam WCS816 geproduceerd bij concentraties lager dan 10^–4 M Fe indien Fe-EDDHA in plaats van Fe-DTPA als ijzerbron aan het cultuurmedium was toegevoegd. Er werd geen effect van beide chelaten gevonden op de siderofoorproduktie door WCS417r. Indien een overmaat van het gezuiverde siderofoor van WCS417r werd toegevoegd aan Fe-EDDHA werden een sterkere afname van de kiembuislengte gevonden dan toevoeging aan Fe-DTPA. De reductie van de kiembuislengte bleek niet volledig verklaard te kunnen worden door een afname van de ijzerbeschikbaarheid. Het chelaat EDDHA heeft ook een toxisch effect op conidiën van fusarium.Wij concluderen, dat de waargenomen reductie van de verwelkingziekte door Fe-EDDHA een gevolg is van de afname van de ijzerbeschikbaarheid voorFod. Dit wordt waarschijnlijk versterkt door de ontwikkeling van een antagonistische, fluorescerendePseudomonas-populatie die sterk concurreren om ijzer. Het additioneel effect dat door bacterisatie metPseudomonas sp. WCS417r van de met Fe-EDDHA behandelde matig resistante anjers (Pallas) werd verkregen is voor een deel het gevolg van een directe concurrentie om ijzer tussen de sideroforen vanFod stam WCS816 en vanPseudomonas sp. stam WCS417r.     

Quantification of Poinsettia Root Growth by Image Scans or X-ray Computed Tomography Scans in Three Propagation Substrates at Varied Moisture Levels

ABSTRACT

The objective was to refine protocols to quantify rooting of plant cuttings and the water/air microenvironment of substrates using x-ray computed tomography (CT). Poinsettia (Euphorbia pulcherrima) cuttings were propagated in three substrates (peat, rockwool, and phenolic foam) at varied moisture levels. In Experiment 1, adventitious rooting occurred in cuttings grown in rockwool or foam from 12% to 86% volumetric water content (VWC) and 12% to 80% volumetric air content (VAC). The highest root growth occurred in rockwool at 59% VWC and 33% VAC. There was an advantage to quantifying root growth by CT in rockwool and foam, in contrast to peat, because of clear differences in material density between root and substrate during image processing. In Experiment 2, root growth was quantified in peat by two-dimensional image scans under similar growth chamber environments, with rapid root growth from 52% to 63% VWC and 16% to 26% VAC. In Experiment 3, CT was used to quantify the substrate microenvironment at 0.5 cm slices to further describe the environment at the base of the plant cutting. Rapid rooting occurred in microenvironments above 56% VWC and 14% VAC, whereas the low 3% VAC in foam at high moisture may limit root growth.

Abbreviations: volumetric water content (VWC), volumetric air content (VAC), volumetric solid content (VSC)     

岩棉短程栽培模式中营养液对番茄生长及果实品质的影响

为实现设施番茄短程栽培过程中营养液的高效供给及标准化管理,寻求短程栽培模式中最优的营养液供给方式,在兼光型植物工厂条件下,研究了营养液电导率值(electric conductivity,EC值)、灌溉频率对番茄植株形态和果实品质的影响.试验以岩棉为栽培基质,3水平EC值为2、4和6 dS/m,3水平灌溉频率为1、3和5次/d,采用全因子试验设计方法,进行9组处理.采用综合评价方法获取最佳的营养液EC值和灌溉频率,并对植株形态和果实品质指标进行数理统计分析.结果表明:营养液EC值和灌溉频率影响植株的株高、茎粗、叶数、叶面积、叶形指数和根面比,同时也影响果实的平均质量、可溶性固形物(soluble solids content)和果形指数.其中EC值对平均果实质量影响显著(P＜0.05),灌溉频率对叶面积和平均果实质量影响极显著(P＜0.01);试验因素的交互作用对茎粗和果形指数影响极显著(P＜0.01),对SSC影响显著(P＜0.05).EC值为4 dS/m,灌溉频率为5次/d的营养液灌溉方式能兼顾植株发育和果实品质良好,该灌溉方式下SSC与平均果实质量呈极显著负相关(P＜0.01).该研究可为设施短程栽培番茄优质高产提供指导依据.     

Micro nutrient uptake of glasshouse cucumbers grown on rockwool

Abstract

The uptake of micro elements by cucumbers grown on rockwool was investigated in a series of experiments. The elements studied in the experiments consisted of iron, manganese, zinc, boron, copper and molybdenum. Five different levels of each of these elements were compared.

The deficiency and excess symptoms were described and the fruit yields were recorded. The trace element contents of the nutrient solution in the root environment were determined by regular sampling. From time to time, samples were also collected of the leaves and fruits of the cucumber crop.

No relationship appeared to exist between the iron contents in the root environment and those in the leaves and fruits. However, relationships were found for all other elements included in the investigation. The relationship between the contents in the root environment and in the crop is curvilinear and can be compute roughly by a function of the model y = ax^b, in which x represents the content of the element in the root environment and y represents the content in the crop.

The limits are given at which deficiency and excess symptoms may be expected.     

SIMULATION MODEL OF WATER AND SOLUTE TRANSPORT IN TWO TYPES OF ROCKWOOL

The aim of this study is to present a two dimensional model for describing the movement of water and solute transport in two types of rockwool slabs – Floriculture, a high density type; and Expert, which has a low density. Water movement is described by the Richards equation, which is implicitly solved using the control volume finite element method. The governing convection dispersion equation describing the solute transport is explicitly solved. Numerical solutions are obtained for the distribution of water and also for the concentration of solute. The model is validated by comparing the results of water transport developed by this model with numerical results obtained by CFD that are validated by experimental results. A composite substrate is tested and validated, and is shown to give good conditions for development of plants.     

岩棉作为草坪草育苗基质的化学安定性初探

通过测定草坪草及其生长液中微量元素的含量,研究岩棉作为草坪草育苗基质的可行性.结果表明:岩棉自身可以释放出大量的微量元素供草坪草初期生长利用;其中释放出的Fe,Cu,Al等微量元素已经超过了草坪草生长需要,过量吸收后容易发生中毒.总之,岩棉具有相对稳定的化学安定性,可以作为草坪草的育苗基质.     

COMPARISON OF YIELD,NUTRIENT SOLUTION CHANGES AND NUTRITIONAL STATUS OF GREENHOUSE TOMATO GROWN IN RECIRCULATING AND NON-RECIRCULATING NUTRIENT SOLUTION SYSTEMS

Studies were carried out in the years 2005–2007 with greenhouse tomato (Lycopersicon esculentum Mill.) cv. ‘Emotion F₁’ grown in rockwool with the recirculating and non-recirculating nutrient solution systems. No significant differences were found in yields of fruits in both systems. In the recirculating system there was more intensive accumulation of sodium (Na), calcium (Ca), chloride (Cl), and zinc (Zn) in the root environment. Leaves of tomato grown in the recirculating nutrient solution system showed a higher content of Ca, magnesium (Mg), and Zn. There were no differences in the contents of nitrates and nitrites in fruits. In the recirculating system, the following savings were recorded: 42.5% of water and (in%): 42.1 nitrogen (N)- ammonium (NH₄), 56.0 N- nitrate (NO₃), 31.4 phosphorus (P), 52.1 potassium (K), 63.5 Ca, 47.9 magnesium (Mg), 49.4 sulfur (S)- sulfate (SO₄), 51.9 Cl, 50.9 iron (Fe), 47.9 Zn, 24.6 manganese (Mn), 53.3 copper (Cu) and 47.2 boron (B). A high effectiveness in decreasing of bacteria number in drain water by UV irradiation was found.     

REVIEWS—RESENSIES

The effect of various conventional seasoning treatments, restraint, storage, log diameter and position of boards in logs on the twisting behaviour of 19–20 year old P. patula timber was determined. The results indicate a distinct influence of restraint and to a lesser extent of temperature on twist, especially so on boards containing pith associated wood of the 27–36 em diameter class and all the boards, regardless of board position in the log, of the 17–23 em diameter class. The benefit of reduced twist through the application of restraint and higher temperatures was generally maintained after a 12 months storage period. It seems as if P, patula boards remain fairly stable during storage when only small moisture changes take place in the timber but the boards of the 17–23 em log diameter class and especially those containing pith associated wood, increased by 3–6° in twist with a loss in moisture content of only 3%.