The Effects of Growth Substances on the Growth of Tapinanthus bangwensis (Loranthaceae) in vitro

The growth response of Tapinanthus bangwensis (Engler and K.Krause) Danser to exogenous growth substances, indole-3yl-aceticacid (IAA), kinetin, and gibberellic acid (GA₃), not only varieswith the concentrations of each of these substances in the mediumbut follows a similar trend in each case. Kinetin, IAA, andGA₃ were found to enhance growth but not by very appreciableamounts, kinetin being the most effective growth promoter. Highconcentrations of these substances (5.0 and 10.0 ppm) exceptGA₃ were toxic to the parasite. Gibberellic acid induced theproduction of accessory leaves at all the concentrations used.Kinetin was also effective in inducing accessory leaves butonly at a concentration of 1.0 ppm. Some of the lower concentrationsof the growth substances affected significantly some aspectsof the parasite's growth and development. Nevertheless, thegrowth in vitro was still slower than that in vivo.     

Studies on the Development and Establishment of Tapinanthus bangwensis

Tapinanthus bangwensis (Engler and K. Krause) Danser is nothost-specific in the absolute sense. The pattern of developmentup to the production of the first two plumular leaves is essentiallythe same on any host. The parasite, however, shows a preferencefor some hosts but such preference is independent of any characteristicsof the family or order to which the host belongs. Soon aftercontact with the host surface, the haustorium, the functionalroot of the parasite begins the penetration process The actualprocess of invasion is a rapid one and is hidden from view.The effects of crushing, disorganization, and disruption ofhost tissues that attend invasion point unequivocally to penetrationby mechanical action. Considerable though these effects mightbe cessation of growth of the parasite-bearing host branch isneither early nor common.     

Establishment of in vitro Cultures of Tapinanthus bangwensis (Engler and K. Krause) Danser and the Effects of Sugars on Growth

Culturing of organs in vitro has been successfully employedin studies on morphogenesis and nutritional requirements ofparasitic and semi-paraaitic angiosperms. Tapinanthus bangwensis,a semi-parasite, has been successfully cultured on chemicallydefined media. By and large the parasite will thrive well ina medium of mineral salts and sucrose at its optimal concentration(4 per cent). However, the parasite is able to metabolize awide range of sugars most of which show similar concentrationoptima Although the growth in vivo was simulated in vitro inthe early stages, it was found that in the later stages growthin vitro was much slower than growth in vivo. The growth differencesobserved in the different media may reflect some of the physiologicaldifferences that are responsible for the selective nature ofthe parasite's development and establishment on different hosts     

Development of Tapinanthus bangwensis (Engler and Krause) Danser and Contact with the Host

Tapinanthus bangwensis forms a single large union with the host.Initially, the haustorium penetrates the host-cortex by thepressure of growth and enzymic action. On contact with the wood,the haustorium induces meristematic activity in the xylem parenchymaand cambium which leads to the dissection of the host wood andpenetration of haustorial branches between the dissected portions.Vascular contact is made by the formation of adjacent conductingcells in the host and parasite tissues.     

The Identification of Zeatin Glucoside from Coconut Milk

By means of chromatographic, mass spectrometric and enzymatic techniques the major cytokinin in butanol extracts from the milk of Cocos nucifera fruits was identified as zeatin glucoside.     

Identification of Zeatin and Zeatinriboside in Coconut Milk

Zeatin and zeatinriboside were identified from the milk of mature Cocos nucifera fruits. It would appear as if the two compounds are present in roughly equal proportions. Ethyl acetate extraction in a liquid-liquid extractor at an alkaline pH (8.0) proved to be a very efficient method of extracting zeatinriboside. Partitioning with water-saturated n-butanol proved to be the best way of extracting zeatin.     

Mistletoe (Tapinanthus bangwensis Reichenbach) infestation of indigenous and non‐indigenous trees at Amani Nature Reserve,Tanzania

A survey of Tapinanthus bangwensis was carried out in a plantation in the botanic garden at Amani Nature Reserve, which forms part of the East Usambara Mountain, located in the north‐east of Tanzania. A total of 169 trees were examined on four transects of 100 × 50 m (5000 m²) each, located about 700 m apart. Three treatment transects were established in open woodland with a control transect in the closed canopy. Out of 101 trees (81 non‐indigenous and 20 indigenous) examined in the open canopy, T. bangwensis was present on 24; eighteen non‐indigenous and six indigenous. Of all the infested trees, a non‐indigenous species, silky oak (Grevillea robusta) was the most common (37.4%), followed by an indigenous species, mzindanguruwe (Blighia unijugata) with 16.6%. Chi‐squared tests showed that there was no significant difference in frequency of infestation between non‐indigenous and indigenous species (χ² = 0.715, P = 0.5826). t‐Testing showed that T. bangwensis preferred taller and larger trees (t = ? 3.930, P = 0.0002 and t = ? 2.416, P = 0.0175, respectively). No T. bangwensis was found on the 68 trees examined in the closed canopy.     

Some Physiological Aspects of the Relationship between Cocoa, Theobroma cacao, and the Mistletoe Tapinanthus bangwensis (Engl. and K. Krause)

The anatomy and development of a typical Tapinanthus bangwensis-cocoaassociation is described, and it is shown how the mistletoehaustorium grows obliquely through the xylem of its host, causingthe cocoa distal to it to die gradually from desiccation. Inearly development the mistletoe haustorium forms a plate oftissue between the host xylem and phloem, having roughly equalareas of contact with both. Later the ratio of phloem: xylemhaustorial contact decreases. Two experiments using ¹⁴C showed that the mistletoe took productsof photosynthesis from its hosts, in one case against the expecteddirection of flow in the host phloem. A third experiment showedthat no labelled photosynthates produced by the mistletoe weretranslocated into cocoa. It is suggested that in this case hosthypertrophication is stimulated by the stresses set up by haustorialgrowth, rather than by mistletoe-produced hormones.     

The Growth and Development of the Wheat Apex: The Effects of Photoperiod on Spikelet Production and Sucrose Concentration in the Apex

Spring wheat (Triticum aestivum cv. Warimba) plants were grownin a controlled environment (20°C) in two photoperiods (8or 16 h). In the first instance, plants were maintained in eachof the photoperiods from germination onwards at the same irradiance(375 µE m^–2 s^–1). In the second case, allplants were grown in a long photoperiod until 4 days after double-ridgeinitiation when half the plants were transferred to a shortphotoperiod with double the irradiance (16 h photoperiod at225 or 8 h at 475 µE ^–2 s^–1). The rates of growth and development of the apices were promotedby the longer photoperiod in both experiments. Shoot dry weightgain was proportional to the total light energy received perday whereas the dry weight of the shoot apex increased withincreasing photoperiod even when the total daily irradiancewas constant. The principal soluble carbohydrate present in the shoot apexwas sucrose, although low concentrations of glucose and fructosewere found in the apices of long photoperiod plants late indevelopment. Sucrose concentration was invariably greater inthe slow-growing apices of short photoperiod plants, but roseto approach this level in the long photoperiod plants when theterminal spikelet had been initiated. Triticum aestivum, wheat, apex, spikelet initiation, photoperiod, flower initiation     

The Culture of Immature Pea Embryos

Pea embryos of a range of developmental stages were culturedin a defined medium in vitro for up to 16 days. The criticalfactor for successful culture was the osmotic pressure of themedium; for the stages studied this was provided by the incorporationof 18 per cent sucrose in the medium. The growth of embryosof a range of genotypes was compared; small seeded genotypescould grow at comparable rates in vitro to those attained invivo. The amount of protein synthesized in vitro was similarto that attained in vivo, whereas slightly higher and lowerlevels of starch and DNA respectively were attained in vitro.The roles of intrinsic and extrinsic factors in regulating embryogrowth were studied by comparing the growth in culture of embryosof different genotypes and of hybrid embryos derived from reciprocalcrosses. embryo culture, pea embryos, hybrid embryos, osmotic pressure     

Purification and Partial Characterization of Polysaccharides From Coconut Milk

Ethanol-precipitated polysaccharides of the liquid endospermof coconut, Cocos nucifera L., were composed predominantly ofgalactose and arabinose with minor amounts of mannose and glucose.Gel filtration chromatography on Bio-Gel A-0.5 m revealed asingle major peak (Peak A) at the void volume and a minor peak(Peak B) partially included in the column volume. Peak A containedsome uronosyl residues, but was not susceptible to cleavageby endopolygalacturonase, indicating that it does not containsignificant amounts of polygalacturonic acid. Neutral glycosylresidue composition analysis of Peak A showed that it consistedof 72% galactose and 24% arabinose with minor amounts of glucoseand rhamnose. Coconut milk, Cocos nuciferaL, polysaccharides, glycosyl composition     

The Effects of Photoperiod, Glucose and Gibberellic Acid on Growth In Vitro and Flowering of Chenopodium Murale

In vitro culture of long-day plant Chenopodium murale L was established. The effects of photoperiod, glucose and gibberellic acid (GA₃) on flowering and growth in vitro were investigated. Oscillatory changes of photoperiodic sensitivity were noticeable with regard to plant age. The plants induced at the phase of the 1^st and the 3^rd pair of leaves flowered to higher degree than those induced at the phase of 2^nd pair. Plants induced at the phase of the 1^st pair of leaves flowered to 17 % on 5 % glucose-containing medium and the addition of 5 mg dm^-3 GA₃ resulted in maximum flowering (43 %). Neither glucose nor GA₃ were able to compensate for photoperiodic requirements for flowering. Hypocotyl growth was decreased and the 1^st internode elongation and development of leaves were increased due to inductive photoperiodic conditions, as compared to non-inductive ones.     

The Effects of Photoperiod and Mineral Nutrient Supply on Growth and Primordia Production at the Stem Apex of Barley Seedlings

Growth and development of the shoot apex in seedlings of threebarley cultivars was examined in two daylengths (8, 16 h) andat two mineral nutrient levels (x 1, x 0.1). Production of primordiawas greater at the higher nutrient level and in the longer days.The rate of production varied with cultivar but in all casesthe plastochron shortened with transition to spike formation.Early flowering (cv. Clipper) was associated with a high rateof primordial production and early transition to spike formation,late flowering (cv. Proctor) with a low rate of production anda longer vegetative phase. The cultivar Akka showed intermediatecharacteristics. The volume of the apical dome increased linearlywith increasing numbers of primordia, the rate of increase varyingwith cultivar and treatment. Enlargement of the dome was duemainly to increase in cell number. The transition of the apexto produce spikelet primordia occurred with widely differingvolumes of the apical dome, thus invalidating the hypothesisthat transition is dependent upon attainment of a critical domesize. Although both the rate of production of primordia andenlargement of the dome were markedly affected by photoperiod,both were unaffected when the photoperiodic treatment was givendirectly to the shoot apex. It is considered that the fate of a primordium once initiatedis determined by competition for available metabolites betweenit, other primordia and the apical dome. Hordeum vulgare L, barley, apical dome, primordia, plastochron, cell division     

Effects of Photoperiod and Temperature on Shoot, Root and Rhizome Growth in ThreeLotus uliginosusSchkuhr Populations

The growth of three populations of greater lotus (Lotus uliginosusSchkuhrsyn.L. pedunculatusCav.) was compared at photoperiods of 10,12 and 14 h at a maximum day/minimum night temperature of 21/16°C and at maximum day/minimum night temperatures of 27/22,21/16, 18/13 and 15/10 °C at a photoperiod of 12 h. Shortdays (10 h) favoured root and rhizome development compared tolong days (14 h). A temperature regime of 15/10 °C restrictedrhizome development compared to the 18/13 and 21/16 °C regimes.Shoot growth was restricted at the highest temperature regime(27/22 °C). The cultivar Sharnae had fewer, but heavier,rhizomes than Grasslands Maku; this may indicate adaptationto the dry summers at its site of origin (Algarve, Portugal).The response of rhizome growth to temperature and photoperiodexplains part of the performance of greater lotus in the fieldat a wide range of latitudes. Grazing management to encouragethe persistence ofL. uliginosusin pasture in temperate environmentsmay include the exclusion of grazing livestock in autumn. Inthe sub-tropics, monitoring of rhizome production in the fieldwould be required before deciding the appropriate time intervalbetween grazing.Copyright 1998 Annals of Botany Company Lotus uliginosus(Schkuhr); greater lotus; temperature; daylength; shoots; roots; rhizomes.     

The In Vitro Culture of Immature Barley Embryos on Different Culture Media

Immature barley embryos (Hordeum distichum var. Julia) of between0•20 and 0•80 mm in length, were isolated from thedeveloping grain and cultured in vitro on various culture media.The subsequent development of the embryos was followed overa period of weeks, and where germination ensued the growth rateof shoot and root meristems was compared with in vivo germinationrates. Various growth media were assessed for their abilityto support normal development of immature embryos. A numberof published media failed to support satisfactory developmentof young embryos. The addition of 1–15 per cent coconutmilk to Norstog's Medium I (mineral + vitamin solns) enhancedembryo development and lowered the threshold of viability fromembryos of 0•50 mm in length to 0•35 mm. Althoughin many cases germination ensued, embryo development was largelyabnormal. A slightly greater enhancement of growth was achievedwith 0•05–0•30 per cent casein hydrolysate asthe growth medium supplement, although abnormal developmentwas not eliminated. A further lowering of the viability thresholdto include embryos of 0•25 mm in length was obtained bycombining 2•7 mM glutamine with the casein hydrolysatesupplement. Normal development and germination of embryos assmall as O25 mm was however obtained on Norstog's Medium JJand the results were reproduced in four additional if . distichumvarieties. In each case the critical threshold of viabilitywas found to lie in embryos of 0•20–0•30 mmin length.     

The Effects of Photoperiod on Flower-bud Development in Phaseolus vulgaris

For a variety of Phaseolus vulgaris of Peruvian origin, extendingthe daylength from 11 to 15 or 16 h with low-intensity incandescentor natural light, while not affecting the rate of initiationof flower primordia, inhibited the development of the flowerbuds and caused many, and sometimes all of them, to senesceand abscise. The inhibition of the oldest flower bud was firstdetected at the stage of pollen formation. The long photoperiodsalso inhibited the elongation and over-all development of theterminal inflorescence but, in contrast, promoted the elongationof those internodes below the first trifoliate leaf and alsothe elongation of the petioles.     

无土栽培下酸铝耦合对银杏生长的胁迫效应

本试验采用U₂₀₇均匀设计方案,通过无土栽培方法研究酸铝耦合处理对银杏幼株生长的效应。结果表明,在pH 4.5～5.5范围内,能耐铝（AlCl₃）浓度可达0.4 mmol/L,而高浓度（0.8～1.2 mmol/L）的铝对银杏有毒害作用;pH高于5.0时,提高培养液中铝浓度对银杏生长无明显影响。总之,酸铝耦合加剧对银杏植株的毒害作用,尤其对根系的伤害更为明显,甚至导致烂根死根,从而使地上部停止生长。     

The Effects of Increasing UV-B Radiation on Pigmentation, Growth and Survival of Coregonid Embryos and Larvae

In the northern regions UV-B radiation levels have increased due to ozone depletion. A two-week laboratory experiment was conducted to measure the effects of UV-B radiation on the pigmentation, growth, oxygen consumption rate and survival of whitefish, Coregonus lavaretus, and vendace, Coregonus albula, larvae. In May newly hatched embryos were exposed in laboratory aquaria to three CIE weighted UV-B radiation levels: subambient (daily dose 1.37kJm^–2), 9% (1.81kJm^–2) and 34% higher (2.24kJm^–2) than ambient. Control embryos and larvae were not exposed to UV-B. Larvae of whitefish and vendace that were irradiated with highest UV-B level had 32% and 31% more melanin than control larvae, respectively, which we interpret as an apparent induced response. In controls, the species difference revealed 53% more melanin in vendace larvae than in whitefish larvae. UV-B radiation had no effect on the mortality of either species, the survival being high in all treatments (>90%). Additionally, neither growth rate nor the metabolic rate of larvae of either species was affected by UV-B radiation. Thus, in relation to future scenarios UV-B radiation may not be a threat to whitefish or vendace larvae in current or expected radiation levels.