Haploid plantlets derived by anther culture of Cucurbita pepo

This work was conducted to study the effect of sucrose and 2,4-D combinations on induction of haploid plants of a summer squash cultivar through anther culture; therefore, sucrose was used at 30, 60, 90, 120 and 150 g l⁻¹and 2, 4-D was used at 0.1, 1.0, 2.5 and 5.0 mg l⁻¹on solid MS anther culture medium. Anthers at the mid or late uninucleate microspore stage without filament were excised from sterilized buds and plated on 20 different induction media. The most plantlets resulted from the induction medium supplemented with 150 g l⁻¹sucrose and 5 mg l⁻¹2, 4-D. Root tips from 20 plantlets were cytologically examined under a light microscope. The results revealed ten diploid (2n>= 2x= 40) and ten haploid (2n= x= 20) plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sucrose uptake by cotyledons of Ricinus communis L.: Characteristics,mechanism, and regulation

Cotyledons of Ricinus communis take up externally supplied sucrose at a rate of up to 150 mol/h/g fresh weight, which is very high when compared with other sugar transport systems of higher plants. The uptake of sucrose is catalysed with a K _m of 25 mmol l^–1; at high sucrose concentrations a linear (diffusion) component becomes obvious. Other mono-, di-, or trisaccharides do not compete for sucrose uptake. Sucrose is accumulated by the cotyledons up to 100-fold, whereby most of the transported, externally supplied sucrose mixes with sucrose present in the tissue. At low sucrose concentrations, however; a small unexchangeable internal pool of sucrose becomes evident. Poisons of energy metabolism such as FCCP inhibit uptake and accumulation of sucrose. The transport of sucrose induces an increase of respiration, from which an energy requirement of 1.4 ATP/sucrose taken up can be calculated. Sucrose is taken up together with protons at an apparent stoichiometry of 0.3 protons/sucrose. Other sugars do not cause proton uptake. The K _m for sucrose induced proton uptake is 5 mmol l^–1; the discrepancy to the K _m for sucrose uptake as well as the low proton: sucrose stoichiometry might possibly be caused by a large contribution of diffusion barriers. The estimated proton-motive potential difference would by sufficient to explain an electrogenic sucrose accumulation. The rate of uptake of sucrose is subject to feedback inhibition by internal sucrose. It is also regulated during growth of the seedlings since it develops rapidly during the first days of germination and declines again after the 4th day of germination, though no substantial increase of passive permeability resistance was observed.Abbreviations DMO dimethyloxazolidinedione - FCCP trifluoromethoxy (carbonyl-cyanide) phenylhydrazon - fr. wt. fresh weight     

Photosynthesis, leaf conductance and water relations of in vitro cultured grapevine rootstock in relation to acclimatisation

Leaf net CO₂ uptake and leaf photosynthetic capacity were investigated in micropropagated 41B grapevine rootstock (Vitis vinifera‘Chasselas’×Vitis berlandieri, Mill. De Gr.) plants grown in the presence of four sucrose concentrations (6.25, 12.5, 25.0 or 37.5 g l^?1). Sucrose concentration in the medium during growth in vitro did not affect the leaf photosynthetic performance of plants neither before nor after transplantation. The maximum photosynthetic rate, measured as CO₂-dependent O₂ evolution, was 7.3 µmol m^?2 s^?1 before transplanting and 15.4 µmol m^?2 s^?1 one month after transplantation. The maximum quantum yield of O₂ evolution (on the basis of incident light) was about 0.07 for all sucrose treatments both before and after transplantation. Dry biomass before transplanting was highest in plants grown with 25.0 or 37.5 g l^?1 sucrose in the medium. One month after transplantation the highest dry biomass was also observed for the same treatments. Survival of plants was 100% for all treatments. Leaf conductance to water vapour was always higher in plants before than after transplantation. Both before and after transplanting it increased with increasing light intensity and decreased slightly with increasing CO₂ molar ratio in in vitro plants. Stomata of plants before transplantation were unresponsive to vapour pressure deficit. In vitro plants experience an acute water stress when they are maintained with the whole root system in water and exposed to ambient controlled conditions in a growth chamber. However, there was no wilting of the leaves when similar plants with roots cut off were left in the same conditions. Hydraulic conductivity was low at both root and shoot-root connection levels. It is likely that water supply could be limiting during transplantation because of the low root and root-stem connection conductivity. Water uptake by roots rather than water loss from the shoots would be of primary importance for the maintenance of water balance during acclimatisation.     

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.     

Production of fructosylxyloside by the new fructosyltransferase from Bacillus macerans EG-6

The new fructosyltransferase (FTase) from Bacillus maceransEG-6 showed a broad acceptor specificity, and resulted in the formation of fructosylxyloside (FX) with d-xylose being the most effective acceptor. The optimal FTase concentration for FX production was 0.6 unit per g sucrose, which gave the highest transfer ratio, 83%, of fructosyl moiety from sucrose to d-xylose. Maximum yield of FX was 114 g l^–1with 200 g sucrose l^–1and 300 g d-xylose l^–1.     

Influence of culture density,pH, organic acids and divalent cations on the removal of nutrients and metals by immobilized Anabaena doliolum and Chlorella vulgaris

The potential of alginate-immobilized Anabaena doliolum and Chlorella vulgaris was assessed for removal of nutrients (NO _inf3 ^sup- and NH _inf4 ^sup+ ) and metals (Cr₂O _inf7 ^sup2- and Ni²⁺) at different biomass concentrations (0.05, 0.1, 0.25, 0.49 and 1.22 g dry wt l^-1) and pH values (4 to 10). Though uptake of all these substances was higher in concentrated algal beads (0.25, 0.49 and 1.22 g dry wt l^-1), their rate of uptake was significantly (P<0.001) lower than that of low (0.05 g dry wt l^-1) cell density beads. For A. doliolum, there was no significant difference in uptake rates for beads having densities of 0.05 and 0.1 g dry wt l^-1. Chlorella vulgaris, however, showed maximum efficiency at 0.1 g dry wt l^-1. Uptake of both the nutrients and the metals was maximal at pH 7 followed by pH 8, 6, 9, 10, 5 and 4. Of the different substances (organic acids and divalent cations) used, humic acid was most efficient in decreasing metal uptake. Mg²⁺ was, however, more efficient than Ca²⁺ in decreasing Ni²⁺ uptake. Immobilized algae with a cell density of 0.1 g dry wt l^-1 were the most efficient for nutrient and metal removal at pH 6 to 8.     

<Emphasis Type="Italic">Narcissus</Emphasis> bulblet formation <Emphasis Type="Italic">in vitro</Emphasis>: effects of carbohydrate type and osmolarity of the culture medium

Shoot clump cultures of Narcissus cultivars St. Keverne and Hawera were used to investigate the effects of culture medium carbon supply, type of carbohydrate and osmolarity on in vitro bulblet development. Increasing the medium osmolarity using mannitol or sorbitol, which did not act as substrates for growth, failed to stimulate bulblet formation with either cultivar. An exception to this was a relatively small increase in total bulblet dry weight per culture, in the cultivar Hawera only, caused by adding 30 g l ^–1 sorbitol in combination with 30 g l^–1 sucrose. Simultaneously increasing the medium osmolarity and carbon supply using the metabolisable carbohydrate sources, sucrose, glucose, fructose or an equimolar mixture of glucose and fructose stimulated bulblet production, total dry matter accumulation and partitioning into bulblets. At comparable levels of carbon supply up to 19.0 g l^–1, bulblet development of both cultivars was similar with monosaccharide and sucrose media. This indicates that substrate supply is more important for bulblet development than osmolarity of the culture medium. The cultivar Hawera also showed similar responses to monosaccharide and sucrose media supplying 37.9 g C l^–1, despite the high osmolarity of monosaccharide media (c. 650 m Osm kg^–1, equivalent to –1.6 MPa, compared to 380 m Osm kg^–1 for sucrose medium). However in St. Keverne total dry matter accumulation and dry weight per bulblet were further stimulated only by increasing the sucrose supply from 19.0 to 37.9 g C l^–1, not by increasing the monosaccharide supply. Implications of the findings for Narcissus micropropagation are discussed.     

Sucrose enhances phosphoenolpyruvate carboxylase activity of in vitro solanum tuberosum L. under non-limiting nitrogen conditions

Summary The effect of sucrose on in vitro potato (ev. Kennebec) metabolism was evaluated. Plants were grown in three different media: Murashige and Skoog basal medium containing high nitrogen concentration with 0 or 20 g l⁻¹ sucrose; or modified medium containing reduced nitrogen amount and 20 g l⁻¹ sucrose. Plants fed with 20 g l⁻¹ sucrose and high N exhibited higher phosphoenolpyruvate carboxylase (PEPC) and pyruvate kinase activities and high PEPC protein concentration at 7, 20 and 33 d of culture compared to those grown with 20 g l⁻¹ sucrose and low N, or with 0 g l⁻¹ sucrose and high nitrogen (control). The highest accumulation of starch and sucrose was found in plants grown with sucrose and low nitrogen. This accumulation occurred concomitantly with a reduced enzyme activity resulting from a low utilization of α-ketoglutarate by nitrogen assimilation, when plants were grown with reduced nitrogen. Our investigations on tricarboxylic acid cycle activity showed that sucrose led to the reduction of organic acid amounts in both leaves and roots when high nitrogen was supplied to plants. This was probably due to the intense exit of α-ketoglutarate, which was confirmed by measurements of cytosolic isocitrate dehydrogenase activity. The low leaf glutamine/glutamate ratio observed in plants grown with 20 g l⁻¹ sucrose and high nitrogen compared to their counterparts cultivated with low nitrogen might be due to glutamine conversion into proteins when nitrogen assimilation was intense. These results demonstrate that sucrose enhanced PEPC activity by increasing protein synthesis. They also suggest that sucrose metabolism is involved in the replenishment of the tricarboxylic acid cycle by providing carbon skeletons required to sustain phosphoenolpyruvate utilization during high nitrate assimilation.     

Decoupling of light intensity effects on the growth and development of C3 and C4 weed species through sucrose supplementation

Light availability has a profound effect on plant growth and development. One of the ways to study the effects of light intensity on plant growth and development without the confounding problem of photosynthate availability is sucrose injection/supplementation. A greenhouse experiment was conducted to evaluate the effects of light levels (0% and 75% shade) and sucrose injection (distilled water or 150 g sucrose l(-1)) on three weed species: redroot pigweed (Amaranthus retroflexus L., C4), lambsquarters (Chenopodium album L., C3) and velvetleaf (Abutilon theophrasti Medic., C3). The average total sucrose uptake was 7.6 and 5.9 g per plant for 0% and 75% shading, respectively, representing 47% of the average total weed dry weight. Plants injected with sucrose had greater dry weights and shoot-to-root ratios under both light levels. In spite of sucrose supplementation the reduction in dry matter due to shading was greater for roots and reproductive structures than vegetative shoot tissues, indicating light level regulation of morphological changes resulting in changed C allocation that are independent of photosynthate availability. Dry weights of plants injected with sucrose under 75% shading were not different from distilled water-injected unshaded plants. However, both sucrose-injected and control plants, regardless of their photosynthetic pathways, underwent similar changes in allocation of dry matter and morphology due to shading, suggesting that these effects are strictly due to light intensity and not related to photosynthate availability.     

Up-regulation of sucrose metabolizing enzymes in Oncidium goldiana grown under elevated carbon dioxide

Experiments were conducted in controlled growth chambers to evaluate how increase in CO₂ concentration affected sucrose metabolizing enzymes, especially sucrose phosphate synthase (SPS; EC 2.4.1.14) and sucrose synthase (SS; EC 2.4.1.13), as well as carbon metabolism and partitioning in a tropical epiphytic orchid species (Oncidium goldiana). Response of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) to elevated CO₂ was determined along with dry mass production, photosynthesis rate, chlorophyll content, total nitrogen and total soluble protein content. After 60 days of growth, there was a 80% and 150% increase in dry mass production in plants grown at 750 and 1 100 μl l^?1 CO₂, respectively, compared with those grown at ambient CO₂ (about 370 μl l^?1). A similar increase in photosynthesis rate was detected throughout the growth period when measured under growth CO₂ conditions. Concomitantly, there was a decline in leaf Rubisco activity in plants in elevated CO₂ after 10 days of growth. Over the growth period, leaf SPS and SS activities were up‐regulated by an average of 20% and 40% for plants grown at 750 and 1100 μl l^?1 CO₂, respectively. Leaf sucrose content and starch content were significantly higher throughout the growth period in plants grown at elevated CO₂ than those at ambient CO₂. The partitioning of photosynthetically fixed carbon between sucrose and starch appeared to be unaffected by the 750 μl l^?1 CO₂ treatment, but it was favored into starch under the 1 100 μl l^?1 CO₂ condition. The activities of SPS and SS in leaf extracts were closely associated with photosynthetic rates and with partitioning of carbon between starch and sucrose in leaves. The data are consistent with the hypothesis that the up‐regulation of leaf SPS and SS might be an acclimation response to optimize the utilization and export of organic carbon with the increased rate of inorganic‐carbon fixation in elevated CO₂ conditions.     

In vitro production of sedative galphimine B by cell suspension cultures of Galphimia glauca

The sedative triterpene, galphimine B (1), was detected in cell suspension-batch cultures of Galphimia glauca. The effect of inoculum size, growth regulators and different concentrations of sucrose, nitrates and phosphates was evaluated. A two-stage batch process for biomass production and accumulation of compound 1 was established. Major cellular growth (15 g l^–1 dry wt) was obtained in the first stage with naphthaleneacetic acid (2 mg l^–1) + kinetin (2 mg l^–1). Adding 4 mg 2,4-dichlorophenoxyacetic l^–1 acid in the second stage resulted in the highest accumulation of 1 (0.21 mg g^–1 dry wt) which was 36% higher with respect to calluses and comparable to that obtained from wild plants.     

Mass propagation of ornamental gentian in liquid medium

An efficient system for clonal mass propagation in liquid culture was established for the propagation of ornamental gentian. In a test of the requirements for three cytokinins [6-benzylaminopurine, N-(2-chloro-4-pyridyl)-N′-phenylurea and N-phenyl-N′-1,2,3-thiadiazol-5-yl urea (TDZ)] in combination with 1-naphthaleneacetic acid (NAA), we found that effective propagation of shoots occurred with 0.01 mg l^–1 TDZ in a 300 ml conical flask that contained 100 ml of medium. The propagation of shoots was also affected by the concentrations of macronutrients (KNO₃, NH₄NO₃ and CaCl₂) and sucrose in Murashige and Skoog's (MS) medium, and it was influenced to some extent by the speed of agitation on an orbital shaker. The most efficient propagation of shoots was achieved in full-strength MS medium supplemented with 0.01 mg l^–1 TDZ and 20 g l^–1 sucrose with agitation at 150 rpm. The propagation of shoots was maximal after 6 weeks of culture (140 shoots from five nodal segments in one flask). Large-scale propagation in a 5-l fermenter was attempted using 3 l of MS medium that contained 0.01 mg l^–1 TDZ and 20 g l^–1 sucrose. More than 2,000 shoots were obtained in the fermenter in 5 weeks following the initial cultivation of five nodal segments for 6 weeks in one 300-ml flask. The shoots that had propagated in the fermenter were transferred directly to soil without prior rooting in vitro and were easily acclimatized within 1 month. Received: 7 October 1997 / Revision received: 16 January 1998 / Accepted: 30 January 1998     

Indigo production in hairy root cultures of Polygonum tinctorium Lour.

The transformed root culture of Polygonum tinctorium Lour. was established by infecting leaf explants with Agrobacterium rhizogenes A4. These cultures were examined for their growth and indigo content under various culture conditions. Among the four different culture media tested, SH medium showed the highest yield for root growth (28 mg dry wt/30 ml) and indigo production (152 g/dry wt). In SH medium, 30 g sucrose l^–1, 2500 mg KNO₃ l^–1, 300 mg NH₄H₂PO₄ l^–1 were the best conditions for indigo production at pH 5.7. The production of indigo in hairy roots slightly increased with the addition of 200 mg chitosan l^–1 (186 g/dry wt) and 20 U pectinase l^–1 (181 g/dry wt).     

Arbuscular Mycorrhizal Fungi Enhance Zinc and Nickel Uptake from Contaminated Soil by Soybean and Lentil

Generally, soils in Pakistan are deficient in P and N. Due to intensive cropping and irrigation, Pakistani soils have also become deficient in micronutrients such as Zn, Fe, Cu, and Mn. Arbuscular mycorrhizal fungi, which form symbiotic associations with roots of most land plants, are known to enhance uptake of P and trace elements such as Cu, Ni, Pb, and Zn. The present study was conducted to investigate the role of arbuscular mycorrhizae (AM) in uptake of nickel (Ni) and zinc (Zn) by crops viz. soybean (Glycine max (L.) Merrill) and lentil (Lens culinaris Medic). Zn and Ni were applied as ZnSO₄ 7H₂O and NiCl₂ respectively, in four concentrations (0.0, 1.0, 3.0, and 5.0 g kg^-1 soil). AM inoculum consisted of sand containing sporocarps, spores, and AMF infected root pieces from a pot culture of Glomus mosseae. Control plants received pot culture filtrate containing soil microflora minus AM fungal propagules. A significant difference (p < 0.05) was observed in the dry weights of roots and shoots of the mycorrhizal (M) and nonmycorrhizal (NM) cereal plants. The sievate-amended treatments did not stimulate plant growth to the same extent as the AM fungal amended treatments. Trace metals inhibited the extent of mycorrhizal colonization of the cereal roots. The concentrations of the trace metals in the plant tissues of 12-week old cereal plants were found significantly (p < 0.05) higher in M than NM plants. These results indicate that mycorrhize can be used as effective tools to supply sufficient Zn in generally Zn-deficient Pakistani soils and to ameliorate the toxicity of trace metals in polluted soils. The contents of Ni in mycorrhizal soybean plant tissues were higher than those in the mycorrhizal lentil plant tissues. The implications of these results in mycorrhizo remediation of agricultural soils are discussed.     

The effect of different kinds of electrolyte and non‐electrolyte solutions on the survival rate and morphology of zebrafish Danio rerio embryos

The effect of electrolyte and non‐electrolyte solutions on the survival and on the morphology of zebrafish Danio rerio embryos was investigated. Embryos in different ontogenetic stages were incubated in electrolyte (NaCl, KCl, MgCl₂ and CaCl₂) and non‐electrolyte solutions [sucrose and polyvinylalcohol (PVA)] of different concentrations for 5 – 15 min. The embryos were hatched to the long‐pec stage and the effective concentrations which caused a 50% decrease in embryo development (EC₅₀) were determined. The morphometric changes, which were caused by the test solutions, were measured. Ion channel blockers were used to see if active ion transport played a role for embryo survival. Finally, dechorionated embryos were exposed to the test solutions to get indications about the importance of chorion and perivitelline space. For 12 hours post fertilization (hpf) embryos and a 15 min exposure period, EC₅₀ was highest for MgCl₂ (1·60 mol l^?1), followed by sucrose (0·73 mol l^?1), NaCl (0·49 mol l^?1), KCl (0·44 mol l^?1), CaCl₂ (0·43 mol l^?1) and PVA [0·0005 mol l^?1 (2·2%)]. EC₅₀ were lower for early embryonic stages than for advanced stages for all solutions with exception of MgCl₂ and sucrose. At the EC₅₀, MgCl₂ and CaCl₂ solutions did not induce morphometric changes. NaCl and sucrose solutions induced reversible morphometric changes, which were compensated within 10 min. Only the EC₅₀ of KCl and PVA solutions induced permanent morphometric changes, which could not be compensated. Incubation of embryos in electrolyte and non‐electrolyte solutions together with ouabain (blocker of Na⁺– K⁺ ATPase), HgCl₃ (dose‐dependent inhibition of aquaporine channels), verapamil (inhibition of calcium and magnesium uptake) and amiloride (inhibition of sodium uptake) significantly decreased the per cent of embryos developing to the long‐pec stage in comparison to the same solutions without blockers. Ouabain and HgCl₃ also induced morphometric changes. For dechorionated embryos the survival rates in water and in the different test solutions were similar to untreated embryos.     

Prospecting the utility of a PMI/mannose selection system for the recovery of transgenic sugarcane (<Emphasis Type="Italic">Saccharum</Emphasis> spp. hybrid) plants

For the first time, the phosphomannose isomerase (PMI, EC 5.3.1.8)/mannose-based “positive” selection system has been used to obtain genetically engineered sugarcane (Saccharum spp. hybrid var. CP72-2086) plants. Transgenic lines of sugarcane were obtained following biolistic transformation of embryogenic callus with an untranslatable sugarcane mosaic virus (SCMV) strain E coat protein (CP) gene and the Escherichia coli PMI gene manA, as the selectable marker gene. Postbombardment, transgenic callus was selectively proliferated on modified MS medium containing 13.6 μM 2,4-D, 20 g l⁻¹ sucrose and 3 g l⁻¹ mannose. Plant regeneration was obtained on MS basal medium with 2.5 μM TDZ under similar selection conditions, and the regenerants rooted on MS basal medium with 19.7 μM IBA, 20 g l⁻¹ sucrose, and 1.5 g l⁻¹ mannose. An increase in mannose concentration from permissive (1.5 g l⁻¹) to selective (3 g l⁻¹) conditions after 3 weeks improved the overall transformation efficiency by reducing the number of selection escapes. Thirty-four vigorously growing putative transgenic plants were successfully transplanted into the greenhouse. PCR and Southern blot analyses showed that 19 plants were manA-positive and 15 plants were CP-positive, while 13 independent transgenics contained both transgenes. Expression of manA in the transgenic plants was evaluated using a chlorophenol red assay and enzymatic analysis.     

Chemical potential of Aphelandra sp. cell cultures

Six different callus lines and three different suspension culture lines were established from plants of two Aphelandra species (Acanthaceae). All established lines were analyzed for secondary metabolite accumulation. A discrepancy between secondary metabolites accumulated in the plants and in the cell cultures could be observed. All established Aphelandrasp. cell cultures produced verbascoside (acteoside) as the major extractable metabolite. Time course experiments were carried out to investigate the relationship between cell growth and verbascoside production. In the present study it was shown that verbascoside accumulation was growth dependent and positively related to the presence of 2,4-D in the medium. The conditions in which verbascoside represents ca. 18% of cell culture weight have been defined. Free polyamines were detected in the cell culture lines cultivated in MS liquid medium (cysteine 10 mg l^-1, thiamine 1 mg l^-1, 2,4-D 1 mg l^-1, kinetin 0.2 mg l^-1 and sucrose 30 g l^-1). Putrescine and spermidine accumulated within 8 days to a maximum of 8.4 μmol g^-1 of dry wt and 2.6 μmol g^-1 of dry wt respectively and thereafter their concentration decreased rapidly. There was no evidence for the presence of spermine or any other type of free or conjugated polyamines in the tested cell culture lines. This revised version was published online in June 2006 with corrections to the Cover Date.     

Callus induction and somatic embryogenesis of Phalaenopsis

Callus induction and plant regeneration through somatic embryogenesis in Phalaenopsis Richard Shaffer `Santa Cruz' were examined. Protocorm-like body (PLB) segments formed calli in Vacin and Went medium with sucrose. The optimal concentration of sucrose was 40 g ⋅ l^–1. Medium containing 200 ml ⋅ l^–1 coconut water together with 40 g ⋅ l^–1 sucrose was effective for callus induction. Gellan gum was suitable than agar as a gelling agent for callus induction. The calli easily formed PLBs after being transferred to a medium without sucrose. Histological observation suggested that the PLBs were somatic embryos. No variation was observed in the flowering plants regenerated through somatic embryogenesis. Received: 11 June 1997 / Revision received: 6 October 1997 / Accepted: 18 October 1997     

Sophorolipid Production with High Yields on Whey Concentrate and Rapeseed Oil without Consumption of Lactose

Sophorolipids were produced by single-step batch cultivation of Candida bombicola ATCC 22214 on deproteinized whey concentrate and repeated feed of rapeseed oil. A mild sterilization method for whey was developed. High yields of 280 g dry sophorolipids l^–1 were obtained from deproteinized whey concentrate containing 100 g lactose l^–1 and 300 g rapeseed oil l^–1. Surprisingly, the whey lactose was not consumed by the organism. Growth only on the oil was assumed and a high lipase activity of 24 U per g cell dry weight resulted.     

CO<Subscript>2</Subscript>-enriched microenvironment affects sucrose and macronutrients absorption and promotes autotrophy in the <Emphasis Type="Italic">in vitro</Emphasis> culture of kiwi (<Emphasis Type="Italic">Actinidia deliciosa</Emphasis> Chev. Liang and Ferguson)

In traditional in vitro culture, the low CO₂ concentration inside the vessels restricts photosynthesis and necessitates the addition of sucrose to the culture medium as the main energy source, thus bringing about changes in the absorption of mineral elements from the culture medium. In this study, we investigated macronutrient absorption and sugar consumption in Actinidia deliciosa Chevalier Liang and Ferguson cv. Hayward (kiwi), cultured on medium supplemented with varying amounts of sucrose (0, 10, and 20 g l⁻¹) under both heterotrophy and autotrophy, flushed with different concentrations of CO₂ (non-ventilation, 300, 600, and 2,000 μl l⁻¹). In ventilated systems with 20 g l⁻¹ of sucrose, sucrose absorption was less than under non-ventilation. The lowest rate of sucrose absorption was recorded when the explants were cultured on medium supplemented with 20 g l⁻¹ of sucrose and flushed with 600 μl l⁻¹ CO₂. Absorption of NO₃ ⁻, PO₄ ³⁻, and Mg²⁺ were high (maximum) at the end of the culture period (40 d) in explants flushed with 600 μl l⁻¹ CO₂ that have been cultured 20 d in the presence of sucrose and then transferred to a sucrose-free medium. These autotrophic conditions promoted maximum plant growth in terms of both fresh and dry mass as well as the length and number of shoots and leaves. The study shows that to maintain an optimum regime of mineral nutrition for prolonged culture of kiwi in vitro, an increased amount of these three ions should be supplemented in Murashige and Skoog’s medium.