A model of seaweed growth in an outdoor culture in Israel

The agarophyte red seaweed Gracilaria conferta was used as a model plant to study the relationship between growth and environmental factors. This species was cultured in small outdoor tanks with continuous seawater supply during three years. Seaweeds were kept under constant density by weekly thinning and were also pulse-fed weekly with nitrogen and phosphate. Water temperature and underwater irradiance increase had opposite effects on the weekly growth rate in two seasons: negative in summer and positive in non-summer. Therefore, a dichotomic separation between summer (June–August) and non-summer (September–May) seasons was utilized in the proposed linear model. The linear model, of the analysis of covariance type, accounted for an explained percentage of total variation (R²) of 0.567, with significant coefficients of all variables included. A standardized model showed that season was the dominant variable, with its coefficient being twice that of temperature in summer, and zero in the non-summer season. Water temperature affected the growth rate twice as much as irradiance, and epiphytes showed a significant negative effect on growth only in the summer. This model aids in the prediction of growth on a seasonal basis under local conditions.     

Effect of nutrient pulse concentration and frequency on growth ofGracilaria chilensis plants and levels of epiphytic algae

The effect of nutrient pulse concentration and frequency onGracilaria chilensis Bird, McLachlanet O Oliveira growth and epiphyte abundace was investigated for plants grown in an indoor culture facility. The frequency of nutrient pulses (which ranged from 1 pulse to 4 pulses per 14 days) had a strong influence on plant growth, while pulse concentration (from 72 to 143 µM as ammonium) had a lesser influence. Growth became a function of total N flux only when plants received nutrient pulses at least twice per 14 days. Both pulse frequency and pulse concentration affected the abundance of epiphytic algae found attached toGracilaria thalli, but pulse frequency was the more significant of the two factors. Their effects could be combined into the single factor, total N flux. Both reasonableG. chilensis growth and low levels of epiphytes were achieved under these conditions (20 °C, 25 µ mol photon m^–2 s^–1 PAR) if ammonium was pulsed at relatively high concentrations (up to 150 µM) once every 7 days into otherwise nitrogen-depleted seawater.     

Cultivar and planting date effects on soybean root growth

To avoid late summer drought, soybean [Gylcine max (L) Merrill] producers in many southern and border states of the USA modify their cropping systems. Options include use of unadapted cultivars and changing planting dates. Because root function is important to plant health and yield, this study was conducted to determine if planting date and soybean cultivar affect root growth and distribution. Seeds of one cultivar from each of four maturity groups (MG III, IV, V, and VI) were sown in mid-April, mid-May, and mid-June in 1992 and 1993 on a Tiptonville silt loam near Portageville, MO. Root observations were performed 30 and 60 days after emergence (DAE) using a minirhizotron system. Cultivars differed for root length density (RLD) only in the 15 to 28 cm depth in 1992 and in the 15 to 28 cm and 29 to 42 cm depths in 1993, but differences were not related to maturity classification of cultivar. Average RLD was 1.02 cm^–3 for MG III and IV cultivars and 1.21 cm cm^–3 for MG V and VI cultivars. Average RLD for the mid-June planting date was 1.65 cm cm^–3 but only 0.73 cm cm^–3 for the mid-April planting date. An increase in RLD between 30 and 60 DAE occurred at all soil depths. For both years, MG V and VI cultivars produced higher yields than the MG III cultivars. Earlier than normal planting dates inhibited early root growth, but did not reduce yield. Cultivars differed only slightly for the rooting characteristics measured in this study. These rooting characteristics may not be important criteria for cultivar selection.Abbreviations MG maturity group - VCR videocassette recorder - DAE days after emergence - RLD root length density - CRLD change in root length density Contribution from the Missouri Agric. Exp. Station Journal Series Number 12, 153Contribution from the Missouri Agric. Exp. Station Journal Series Number 12, 153     

水分和种植密度对干热河谷车桑子生长性状及种内相互关系的影响

水分是干热河谷植物生长过程中最主要的限制因子,种植密度增加也会引起植物生长的资源限制,两者交互作用下植物生长性状及种内关系的变化特征还不清楚。以干热河谷优势植物——车桑子为研究对象,根据元谋干热河谷年均生长季降雨量设置3种水分梯度:高水分、中水分和低水分,同时在各水分梯度下设置4个种植密度:1、2、4、9株/盆,探究水分、种植密度及其交互作用对车桑子生长性状、生物量分配及种内相互作用的影响。结果表明:(1)低水分条件下,车桑子生长和水分生理受到抑制,但车桑子在较低的叶水势下依然能够保持较高的相对含水量;(2)干旱胁迫显著降低了车桑子总生物量和单株生物量,显著增加了枯叶生物量比例,低水分和中水分条件下,增加种植密度对总生物无显著影响;而高水分条件下,增加种植密度显著提高了车桑子总生物量;(3)低水分显著增加了茎、叶生物量的异速生长指数,将更多生物量分配到叶,而种植密度增加显著降低了茎、叶生物量的异速生长指数,增加了茎的生物量分配;(4)通过相对邻体效应的计算,各处理条件下,车桑子种内关系均表现为竞争作用,并且,这种竞争作用的强度随水分的减少和密度的增加而增加。在高密度条件下(9棵/盆),...     

Influence of ammonium-N pulse concentrations and frequency,tank condition and nitrogen starvation on growth rate and biochemical composition ofGracilaria gracilis

The growth rate ofGracilaria gracilis maintained in tanks at an abalone farm near Port Elizabeth, South Africa, was examined under various tank conditions and NH₄-N pulse frequencies and concentrations. This was accompanied by analyses of the components of the internal nitrogen pool. A maximum growth rate of ca. 35% wk^–1 was obtained at 1200 M NH₄-N. The alga was able to grow at non-nitrogen limited rates using only internal stored nitrogen to sustain growth for one week before the growth rate decreased to ca. 17% per week. NH₄-N pulse frequency did not affect growth rate but one pulse per week led to a marked decrease in total-N, protein, phycoerythrin and chlorophyll-a content. An increase in pulse frequency to two pulses per week doubled the protein content from 2.351 ± 0.143 to 4.453 ± 0.090% (per unit dry mass). Carbohydrate content was inversely related to nitrogen storage. The growth rate in fouled tanks was always lower than in clean tanks. It seems likely that seaweeds and diatoms colonising the tank sides reduced light reflected off the inside of a tank, thereby reducing the growth rate.     

Causes and implications of intra-clonal variation in Gracilaria chilensis (Rhodophyta)

Strain selection studies in Gracilaria chilensis detected significant levels of intra-clonal variation. These findings motivated more detailed studies on the causes and implications of intra-clonal variation in these and other red algal species. Our results indicate that intra-clonal variation is common among replicated units (e.g.: carpospores and ramets) of several red algal species and suggest that a larger data base probably will show the occurrence of various kinds of intra-clonal changes, differing in frequency of occurrence and magnitude of phenotypic expression. It is likely also that different species would exhibit different amounts of variation. Four types of factors may cause intra-clonal variation: (1) physiological or developmental differences among ramets, (2) localized pathogen infections, (3) several kinds of genetic changes, and (4) sporeling coalescence. Intra-clonal variation among ramets: (1) increases the possibility of genet survival, (2) explains the origin of morphological and physiological differences among ramets of a given genet, (3) explains the large population variation found in many clonal species and (4) suggests that strain selection of some economically important seaweeds should be thought of as a fairly continuous process due to the instability of some of these clones.     

Agar yield and quality of Gracilaria chilensis (Gigartinales,Rhodophyta) in tank culture using fish effluents

Tank cultivation of Gracilaria using fish effluents has permitted a production of 48 kg m^–2 yr^–1 and can reduce the dissolved nitrogen loads in the seawater. We report the yield, gel strength, gelling and melting point of agar from Gracilaria cultivated in tanks with seawater previously utilized in intensive, land-based salmon cultures and compared to a control using directly pumped seawater, over a study period of 22 months. The results show that the highest agar yield (20 to 22%) was obtained when Gracilaria was cultivated with pure seawater as compared to the fish effluents. The gel strength, gelling and melting point were higher in the agar obtained from algae cultured with fish effluents. During the spring, the gel strength, gelling and melting point increased in tanks with fish effluents and decreased in tanks with a supply of pure seawater.     

Influence of enhanced CO2 on growth and photosynthesis of the red algaeGracilaria sp. andG. chilensis

The influence of elevated CO₂ concentrations on growth and photosynthesis ofGracilaria sp. andG. chilensis was investigated in order to procure information on the effective utilization of CO₂. Growth of both was enhanced by CO₂ enrichment (air + 650 ppm CO₂, air + 1250 ppm CO₂, the enhancement being greater inGracilaria sp. Both species increased uptake of NO₃ ^– with CO₂ enrichment. Photosynthetic inorganic carbon uptake was depressed inG. chilensis by pre-culture (15 days) with CO₂ enrichment, but little affected inGracilaria sp. Mass spectrometric analysis showed that O₂ uptake was higher in the light than in the dark for both species and in both cases was higher inGracilaria sp. The higher growth enhancement inGracilaria sp. was attributed to greater depression of photorespiration by the enrichment of CO₂ in culture.     

Effects of surfactants on cell growth and pigment production in suspension cultures ofPerilla frutescens

The effects of surfactants, adecanol LG-294 and silicone A, on anthocyanin accumulation and the growth ofPerilla frutescens cells in suspension cultures were studied. Production of the red pigment was remarkably reduced from about 1.9 g/l to 0.4 g/l by adecanol LG-294 at 0.06 ml/l but not by silicone A up to 0.4 ml/l. Several repeated shake-flask cultures also demonstrated no adverse effects of silicone A on the metabolite accumulation by the suspended cells. Furthermore, the addition of silicone A to a culture in a stirred bioreactor produced a three-fold higher growth rate and a seven-fold increase in anthocyanin compared with surfactant-free cultures. The improvement was due to the substantial reduction or prevention of foaming and of cell adhesion to the bioreactor wall.     

Effects of phosphate and nitrate supply on productivity,agar content and physical properties of agar ofGracilaria strain G-16S

Gracilaria strain G-16S was cultured in various phosphorus (P) supply rates with low or high nitrogen (N) supply to determine the effects of nutrient supply on its productivity, agar content and physical properties of the agar. Productivity was reduced after four weeks of growth in zero P supply as plants reached 0.07% P tissue content (critical level), with fragmentation of these plants by six weeks (0.05% P; minimum viable level). Native agar content was higher in low P and high N, or low N conditions. Agar content appeared to increase with decreasing P under high N supply. This increase was not apparent with alkali treatment prior to extraction. Agar gel strength was greatly increased by alkali treatment. The highest gel strengths were obtained under high N supply at all P supply rates except zero P, and under low N supply at 12 M P week^–1. Native agar gel strengths showed a similar pattern on a lower scale. Melting temperatures were higher in agars with higher gel strengths. Dynamic gelling temperatures were generally high for alkali-treated agar, with agar from plants grown in zero P supply showing a slightly elevated gelling temperature. Melting and gelling temperatures of native agars with the highest gel strengths were in the same range as bacteriological agar. These results show that P and N supply affects productivity, agar content and agar physical properties, but the tradeoffs between a slightly higher agar quantity under nutrient limitation and higher agar quality under nutrient-replete conditions seem to favor the latter.     

High density cell culture of Panax notoginseng for production of ginseng saponin and polysaccharide in an airlift bioreactor

High cell density of Panax notoginseng in a 17 l airlift bioreactor was achieved in batch cultivation using a modified MS medium. The dry cell weight, ginseng saponin and polysaccharide reached 24, 1.7 and 2.8 g l^–1, respectively, after 15 d. A strategy of sucrose feeding based on changes in the specific O₂ uptake rate was applied to the cell cultures, which increased these respective yields to 30, 2.3 and 3.2 g l^–1.     

A simple wheat haploid and doubled haploid production system using anther culture

Summary Wheat (Triticum aestivum L.) haploids and doubled haploids have been used in breeding programs and genetic studies. Wheat haploids and doubled haploids via anther culture are usually produced by a multiple step culture procedure. We improved a wheat haploid and doubled haploid production system via anther culture in which plants are produced from microspore-derived embryos using one medium and one culture environment. In the improved protocol, tillers of donor plants were pretreated at 4°C for 1–2 wk before anthers were plated on a modified 85D12 basal medium with phenylacetic acid (PAA) and zeatin and cultured at 30°C with a 12-h daylength (43 μEs⁻¹m⁻²) in an incubator. Microspore-derived embryos developed in 2–3 wk and the plants were produced 3–4 wk after anther plating. In the improved system, as much as 53% of the anthers of Pavon 76 were responsive with multiple embryos. For plant regeneration, as many as 22 green and 25 albino plants were produced from 100 anthers. Sixty-five green plants were grown to maturity and 32 (49%) plants were fertile and produced seeds (indicating spontaneous chromosome doubling) while 33 plants did not produce seed. Of five Nebraska breeding lines tested using the protocol, NE96675 was very responsive and the other lines less so, indicating that the protocol is genotype-dependent.     

Suspended cultivation of Gracilaria in the sea

Suspended rope cultivation systems for Gracilaria or Gracilariopsis can be seeded from spores but vegetative propagation is used for those which are currently commercially successful. Such systems and methods have been recently developed for the shallow lagoon areas around Lüderitz, Namibia and deeper open water sites off the Araya Peninsula, Venezuela. Various sites, substrata, depths and seeding methods have been assessed and have resulted in average commercial growth rates of about 3.5% per day. Netlon ‘Superope’ has been demonstrated to be more suitable than laid rope as a substratum for outplanted vegetative Gracilaria gracilis in Namibia as it does not compress the thalli as they grow. An efficient method, using hooks, has been developed to ‘seed’ the Superope. There is a very low incidence of algal epiphytism: mainly Ceramium and Ulva sp. In Venezuela, pilot rope cultivation systems for Gracilariopsis tenuifrons proved successful and have good commercial prospects.     

Improvement in growth and toxin production of Alexandrium tamarense by two-step culture method

The growth and toxin content of the dinoflagellate Alexandrium tamarense ATHK was markedly affected by culture methods. In early growth phase at lower cell density static or mild agitation methods were beneficial to growth, but continuous agitation or aeration, to some extent, had an adverse effect on cell growth. Static culture in 2 L Erlenmeyer flasks had the highest growth rate (0.38 d⁻¹) but smaller cell size compared with other culture conditions. Cells grown under aerated conditions possessed low nitrogen and phosphorus cell yields, namely high N and P cell-quota. At day 18, cells grown in continuous agitated and 1 h aerated culture entered the late stationary phase and their cellular toxin contents were higher (0.67 and 0.54 pg cell⁻¹) compared with cells grown by other culture methods (0.27–0.49 pg cell⁻¹). The highest cell density and cellular toxin content were 17190 cells mL⁻¹ and 1.26 pg cell⁻¹ respectively in an airlift photobioreactor with two-step culture. The results indicate that A. tamarense could be grown successfully in airlift photobioreactor by a two-step culture method, which involved cultivating the cells statically for 4 days and then aerating the medium. This provides an efficient way to enhance cell and toxin yield of A. tamarense.     

不同水分条件下混种密度对芦苇和反枝苋种间竞争的影响

与本地植物的种间竞争是影响外来植物能否成功入侵的关键因素之一,该研究通过受控模拟试验研究了本地植物芦苇(Phragmites australis)和外来入侵植物反枝苋(Amaranthus retroflexus)在淹水和干旱两种水分条件下混种密度(6∶2、4∶4和2∶6)对其种间竞争的影响。结果表明:(1)芦苇和反枝苋的相对产量与相对产量总和均小于1,即两种植物存在种间竞争。(2)种间竞争使芦苇和反枝苋的生长均受到了不同程度的抑制,表现在两者的株高和生物量均随着竞争者密度的增加而降低。(3)植株地上部分和地下部分的氮浓度表现出与株高和生物量相同的趋势,且在不同水分条件下存在差异。(4)芦苇和反枝苋分别在淹水和干旱环境下具有较强竞争力,但在各自较高混种密度下亦具有较强竞争力。可见,芦苇和反枝苋的种间竞争受到了水分和混种密度的影响。因此,在有反枝苋分布的湿地中,植物生长初期可通过增加土壤水分和/或增加芦苇等本地植物的种群密度以降低反枝苋的种群密度来限制其竞争能力,防止反枝苋在湿地中生长建群和扩散入侵。     

Biomass production in mixotrophic culture of Euglena gracilis under acidic condition and its growth energetics

When Euglena gracilis was grown in the heterotrophic condition with glucose and (NH₄)₂SO₄ as the carbon and nitrogen source, a high cell yield (4.28–4.48 g l^–1) was obtained and the culture pH decreased to 1.6–2. The biomass production in the heterotrophic culture was compared to those in the autotrophic and mixotrophic cultures. Autotrophic growth was 4.7–6.3% of the heterotrophic one, whereas about 15–19% higher growth was obtained in the mixotrophic culture. Moreover, good production of chlorophyll (39.4 mg l^–1) and carotenoids (13.8 mg l^–1) were attained in the mixotrophic culture, giving the highest fermenter productivity with respect to biomass as well as chlorophyll and carotenoids. Through an energetic analysis in the mixotrophic culture, it was estimated about 25–28% of the total ATP requirement is formed in the photochemical reactions. This resulted in an improved biomass production in the mixotrophic culture of E. gracilis.     

The influence of soybean planting density on dinitrogen fixation and yield

We investigated the effect of planting density on soybean (Glycine max (L.) Merr.) yield in glasshouse and field experiments. Because net canopy photosynthesis increases with increasing plant density, we hypothesized that increasing planting density would result in increasing rates of dinitrogen fixation in soybeans and higher yields per unit land area.In glasshouse studies, Wayne variety soybeans were planted in 10-cm diameter pots, 1 plant pot^-1 in matrices of 10-, 15-, 20-, 25-, or 30-cm equidistant intervals. Bradyrhizobium japonicum inoculum was added to half of the plants in each treatment. Replicate measurements of total stem height, internode lengths, leaf mass, stem mass, root mass, nodule number, nodule mass, and nitrogenase activity were obtained at 3, 6, and 9 weeks post-emergence. Fruits were harvested and counted at week 14. As planting density increased there were (1) altered morphology and growth rates, (2) increased apparent specific nodule activity (SNA), (3) decreased nodule number and mass, and (4) nearly constant fruit and seed production/plant. Expressed on a unit area basis, nitrogen influx and yield increased geometrically as planting density increased, with maximum values observed for 10-cm plantings.Field studies of Wayne, Stein, Williams, and Gold Harvest soybean varieties were made in 1985. Plots were established containing 100 plants spaced at 10-, 20-, and 30-cm distances. Measurements made during the growing season and at harvest established the same relative trends identified from the glasshouse studies. Increasing plant densities resulted in higher yields per unit land. Varietal differences were almost significant.     

Response of cowpea to variations in planting density and nutrient level

A greenhouse study was carried out using cowpea (Vigna unguiculata (L.) Walp.) grown in Perlite^® and inoculated with Nitragin^® to investigate the concentration of plant nutrients and planting density required for optimum biomass production. Five concentrations (full, 0.5, 0.2, 0.1 and 0.05 strength) of Bisseling's nutrient solution and five planting densities (one to five plants per pot) were tested in a factorial randomized Graeco-Latin square design. Growth was determined as fresh and dry weights of leaves, stems, petioles, roots, flowers and pods, and whole plant.Optimum biomass production was found at 0.5 strength nutrient solution and a density of one plant per pot. Plants were more sensitive to higher planting density than to alterations of nutrient level. Over a twenty-fold range of nutrient supply, whole plant biomass yield varied at most by 44%, whereas increasing planting density from one to five plants per pot decreased biomass production by as much as 77%. There is a decrease in the shoot/root ratio as nutrient level decreases. The data suggests a potential for higher seed production at the higher densities and lowest nutrient levels, but this data was inconclusive.