The impact of red and blue light-emitting diode illumination on radish physiological indices

The objective was to evaluate the effect of different combinations of red (638 nm) and blue (455 nm) light produced by solid-state light-emitting diodes (LEDs) on physiological indices (net assimilation rate, hypocotyl-to-leaf ratio, leaf area, leaf dry weight, hypocotyl length and diameter, plant length, developed leaves), variation of photosynthetic pigments and non-structural carbohydrates in radish (Raphanus sativus L., var. ‘Faraon’). Lighting experiments were performed under controlled conditions (total PPFD - 200 μmol m⁻² s⁻¹; 16 h photoperiod; 14/18°C night/day temperature). The LED conditions: 638 nm; 638 + 5% 455 nm; 638 + 10% 455 nm; 638 + 10% 455 + 731 nm; 638 + 10% 455 + 731 + 669 nm. Our results showed that radishes grown under red (638 nm) alone were elongated, and the formation of hypocotyl was weak. The net assimilation rate, hypocotyl-to-leaf ratio, and leaf dry weight also were low due to the low accumulation of photosynthetic pigments and non-structural carbohydrates in leaves. The supplemented blue (455 nm) light was necessary for the non-structural carbohydrates distribution between radish storage organs and leaves which resulted in hypocotyl thickening. Red alone (638 nm) or in combination with far-red (731 nm), or red669 for radish generative development was required.     

The Development of Desiccation-tolerance and Maximum Seed Quality During Seed Maturation in Six Grain Legumes

‘Physiological maturity’, i.e. the time when seedsreach their maximum dry weight during development, occurredwhen maturation drying on the parent plant in the field hadreduced seed moisture content to approximately 60 per cent infaba bean (Vicia faba L.), lentil (Lens culinaris Medic.), chickpea(Cicer arietinum L.), white lupin (Lupinus albus L.), soya bean(Glycine max [L.] Merr.) and pea (Pisum sativum L.) The onsetof desiccation-tolerance, i.e. the ability of seeds to germinatefollowing harvest and rapid artificial drying, coincided withphysiological maturity, except in pea where it occurred a littleearlier at about 70 per cent moisture content. Maximum seedquality as determined by maximum viability, minimum seedlingabnormalities and maximum seedling size occurred in pea, chickpeaand lupin when seeds were harvested for rapid drying at physiologicalmaturity; but for maximum seed quality in the other speciesmaturation drying had to proceed further - to about 45 per centmoisture content in soya bean and to about 30 per cent moisturecontent in lentil and faba bean seed crops. Much of this variationamongst the six species, however, was due to differences inthe variation in maturity within each seed crop. Results forindividual pods showed that peak maturity, i.e. maximum seedquality following harvest and rapid artificial drying, was achievedin all six species once maturation drying had reduced the moisturecontent of the seeds to 45–50 per cent. In pea, faba beanand soya bean there was a substantial decline in viability andan increase in seedling abnormalities when harvest was delayedbeyond the optimal moisture content for harvest.     

Comparative Characteristics of Carbohydrate Binding by Lectins from Broad Bean,Pea, Common Vetch,and Lentil Seeds

Lectins from the seeds of broad bean (Vicia faba L.), pea (Pisum sativum L.), common vetch (V. sativa L.), and lentil (Lens culinaris Medik.) were isolated and purified by affinity chromatography. The hemagglutinating activity of lectins was most effectively inhibited by methyl--D-mannopyranoside, trehalose, and D-mannose. Other carbohydrate haptens, such as methyl--D-glucopyranoside, maltose, and alginic and D-glucuronic acids were less effective. Two lectins obtained from different lentil cultivars, unlike other lectins, had a relatively high affinity for melecitose, N-acetyl-D-glucosamine, L-sorbose, and sucrose. Furthermore, these lectins interacted with soluble starch. All the lectins examined had similar, but not identical, carbohydrate-binding properties. Because of their similar D-mannose/D-glucose specificity, these lectins interacted with lipopolysaccharides and exopolysaccharides of Rhizobium leguminosarum bv. viciae, root nodule bacteria that infect broad-bean, pea, common-vetch, and lentil plants with the formation of nitrogen-fixing symbiosis. However, owing to individual distinctions of carbohydrate-binding properties, these lectins showed a higher affinity for the polysaccharides of those microsymbionts within the R. leguminosarum bv. viciae species that were better specialized towards one or the other host plant from the cross inoculation group of legumes.     

Urartian plant cultivation at Yoncatepe (Van), eastern Turkey

Plant remains were recovered from an Urartian settlement, Yoncatepe, situated in the Van province of eastern Turkey and dating to the Iron Age period (first millennium B.C.E.). Large quantities of hulled barley (Hordeum vulgare L.) and of bread/macaroni wheat (free-threshing wheat) Triticum aestivum L./T. durum Desf.), both mixed with small quantities of domesticated emmer wheat (T. dicoccum Schübl.), were found in the storerooms of the Yoncatepe palace, indicating the storage of agricultural surplus. Rye (Secale cereale L.) grains occur very occasionally, while pulses include lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), and bitter vetch (Vicia ervilia [L.] Willd.). Grape seeds unearthed in a tomb at Yoncatepe provide physical evidence supporting written records of vineyards. Numerous seeds of gold of pleasure (Camelina sativa [L.] Crantz), found in a storage vessel, provide evidence of the cultivation of this plant. It is likely, that the Urartians used the seeds for oil extraction.     

Antioxidant properties of essential oils

By the method of capillary gas-liquid chromatography, we studied the antioxidant properties and stability during the storage of hexane solutions of 14 individual essential oils from black and white pepper (Piper nigrum L.), cardamom (Elettaria cardamomum L.), nutmeg (Myristica fragrans Houtt.), mace (Myristica fragrans Houtt), juniper berry (Juniperus communis L.), fennel seed (Foeniculum vulgare Mill., var. dulce Thelling), caraway (Carvum carvi L.), dry cinnamon leaves (Cinnamomum zeylanicum Bl.), marjoram (Origanum majorana L.), laurel (Laurus nobilis L.), ginger (Zingiber officinale L.), garlic (Allium sativum L.), and clove bud (Caryophyllus aromaticus L.). We assessed the antioxidant properties by the oxidation of aliphatic aldehyde (trans-2-hexenal) into the corresponding carbonic acid. We established that essential oils of garlic, clove bud, ginger and leaves of cinnamon have the maximal efficiency of inhibiting hexenal oxidation (80!–93%), while black pepper oil has the minimal (49%). Antioxidant properties of essential oils with a high content of substituted phenols depended poorly on their concentrations in model systems. We studied the changes in the composition of essential oils during the storage of their hexane solutions for 40 days in light and compared it with the stability of essential oils stored for a year in darkness.     

Chromium accumulation, translocation and chemical speciation in vegetable crops

Trivalent chromium (Cr³⁺) is essential for animal and human health, whereas hexavalent Cr (CrO₄ ²⁻) is a potent carcinogen and extremely toxic to animals and humans. Thus, the accumulated Cr in food plants may represent potential health hazards to animals and humans if the element is accumulated in the hexavalent form or in high concentrations. This study was conducted to determine the extent to which various vegetable crops absorb and accumulate Cr³⁺ and CrO₄ ²⁻ into roots and shoots and to ascertain the different chemical forms of Cr in these tissues. Two greenhouse hydroponic experiments were performed using a recirculating-nutrient culture technique that allowed all plants to be equally supplied with Cr at all times. In the first experiment, 1 mg L⁻¹ Cr was supplied to 11 vegetable plant species as Cr³⁺ or CrO₄ ²⁻, and the accumulation of Cr in roots and shoots was compared. The crops tested included cabbage (Brassica oleracea L. var. capitata L.), cauliflower (Brassica oleracea L. var. botrytis L.), celery (Apium graveolens L. var. dulce (Mill.) Pers.), chive (Allium schoenoprasum L.), collard (Brassica oleracea L. var. acephala DC.), garden pea (Pisum sativum L.), kale (Brassica oleracea L. var. acephala DC.), lettuce (Lactuca sativa L.), onion (Allium cepa L.), spinach (Spinacia oleracea L.), and strawberry (Fragaria ×  ananassaDuch.). In the second experiment, X-ray absorption spectroscopy (XAS) analysis on Cr in plant tissues was performed in roots and shoots of various vegetable plants treated with CrO₄ ²⁻ at either 2 mg Cr L⁻¹ for 7 d or 10 mg Cr L⁻¹ for 2, 4 or 7 d. The crops used in this experiment included beet (Beta vulgaris L. var. crassa (Alef.) J. Helm), broccoli (Brassica oleracea L. var. Italica Plenck), cantaloupe (Cucumis melo L. gp. Cantalupensis), cucumber (Cucumis sativus L.), lettuce, radish (Raphanus sativus L.), spinach, tomato (Lycopersicon lycopersicum (L.) Karsten), and turnip (Brassica rapa L. var. rapifera Bailey). The XAS speciation analysis indicates that CrO₄ ²⁻ is converted in the root to Cr³⁺ by all plants tested. Translocation of both Cr forms from roots to shoots was extremely limited and accumulation of Cr by roots was 100-fold higher than that by shoots, regardless of the Cr species supplied. Highest Cr concentrations were detected in members of the Brassicaceae family such as cauliflower, kale, and cabbage. Based on our observations and previous findings by other researchers, a hypothesis for the differential accumulation and identical translocation patterns of the two Cr ions is proposed. Received: 27 February 1998 / Accepted: 2 April 1998     

Photochemical and photophosphorylation activities of chloroplasts and leaf mesostructure in Chinese cabbage plants grown under illumination with light-emitting diodes

Leaf mesostructure, photochemical activity, and chloroplast photophosphorylation (PP) in the fourth true leaf of 28-day-old Chinese cabbage (Brassica chinensis L.) plants were investigated. Plants were grown under a light source based on red (650 nm) and blue (470 nm) light-emitting diodes (LED) with red/blue photon flux ratio of 7: 1 and under illumination with high-pressure sodium lamp (HPSL) at photon flux densities of 391 ± 24 μmol/(m² s) (“normal irradiance”) and 107 ± 9 μmol/(m² s) (“low irradiance”) in photosynthetically active range. At normal irradiance, the leaf area in plants grown under HPSL was twofold higher than in LED-illuminated plants; other parameters of leaf mesostructure were little affected by spectral quality of incident light. The lowering of growth irradiance reduced the majority of leaf mesostructure parameters in plants grown under illumination with HPSL, whereas in LED-illuminated plants the lowered irradiance reduced only specific leaf weight but increased the leaf thickness and dimensions of mesophyll cells and chloroplasts. The photochemical activity of isolated chloroplasts was almost independent of growth irradiance and light spectral quality. Light quality and intensity used for plant growing had a considerable impact on PP in chloroplasts. At normal light intensity, the highest activity of noncyclic PP in chloroplasts was observed for plants grown under HPSL; at low light intensity the highest rates of PP were noted for plants grown under LED. The P/2e⁻ ratio, which characterizes the degree of PP coupling to electron transport in the chloroplast electron transport chain, showed a similar pattern. Thus, the narrow-band spectrum of the light source had little influence on leaf mesostructure and electron transport rates. However, this spectrum significantly affected the chloroplast PP activity. The PP patterns at low and normal light intensities were opposite for plants grown under LED and HPSL light sources. We suppose that growing plants under LED array at normal light intensity disturbed the chloroplast coupling system, thus preventing the effective use of light energy for ATP synthesis. At low light intensity, chloroplast PP activity was significantly higher under LED illumination, but plant growth was suppressed because of impaired adaptation to low light intensity.     

Photosynthetic light-harvesting function of carotenoids in higher-plant leaves exposed to high light irradiances

Exposure of barley (Hordeum vulgare L.) leaves to strong white light (1500 μmol photons · m⁻² · s⁻¹) decreased the quantum yield of photosynthetic oxygen evolution in green light preferentially absorbed by carotenoids (Φ-510) but not in red light exclusively absorbed by chlorophylls (Φ-650). This phenomenon was observed to be (i) rapidly induced (within a few minutes), (ii) slowly reversible in darkness (within about 1 h), (iii) insensitive to dithiothreitol and (iv) maximally induced by photon flux densities higher than about 1000 μmol · m⁻² · s⁻¹. Determination of the carotenoid composition of the major light-harvesting complex of PSII (LHCII) and analysis of the thylakoid membrane lipid fluidity before and after strong illumination of barley leaves in the presence or the absence of dithiothreitol showed that the light-induced decrease in the Φ-510/Φ-650 ratio did not require the physical detachment of carotenoids from the pigment antennae. Compared to barley plants grown under moderate light and temperature conditions, plants grown in sustained high irradiance at elevated temperature exhibited (i) a lower Φ-510/Φ-650 ratio, (ii) a reduced size of the functional PSII pigment antenna in green light (but not in red light) and (iii) a marked increase in the amount of free carotenoids found in non-denaturing Deriphat-containing electrophoretic gels of thylakoid membranes. Similarly, the Φ-510/Φ-650 ratio of the LHCII-deficient chlorina-f2 barley mutant was very low compared to the wild type. Separation and quantification of the cis/trans carotenoid isomers of barley leaves revealed that strong illumination did not induce pronounced cis-trans isomerization of xanthophylls. Taken together, the data suggest that the efficiency of energy transfer from carotenoids to chlorophylls varies with the light environment both in the short term and in the long term, with excess light energy noticeably inhibiting the photosynthetic light-harvesting function of carotenoids. The photoprotective significance of this carotenoid decoupling from the chlorophyll antennae is discussed. Received: 28 July 1997 / Accepted: 25 October 1997     

Effect of light-emitting diodes on growth and morphogenesis of upland cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) plantlets in vitro

The objective of this study was to determine the effects of different light-emitting diode (LED) light sources on the growth of upland cotton (Gossypium hirsutum L.) plantlets. Shoot bud apex cuttings of upland cotton (1.0 cm) were transplanted on Murashige and Skoog (MS) basal medium supplemented with 0.1 mg/l 6-benzyladenine (BA) and 0.5 mg/l naphthalene acetic acid (NAA) and cultured in vitro for 45 days. They were exposed to 50 μmol m⁻² s⁻¹ photosynthetic photon flux (PPF) and a 12-h photoperiod under six different lights: fluorescent lamp (CON), monochromatic blue LED (B), three blue and red LED mixtures (B:R = 3:1, 1:1, 1:3) and monochromatic red LED (R). The effects of the six light sources on growth and morphogenesis of upland cotton plantlets grown in vitro were investigated. Fresh weight, dry weight, stem length and second internode length were greatest in plantlets cultured under the B:R = 1:1 blue and red LED light, followed by blue LED light, and they were lowest in plantlets cultured under a fluorescent lamp. Chlorophyll content, leaf thickness, palisade tissue length, leaf and stomata area were highest in plantlets cultured under blue LED light. Root activity, sucrose, starch and soluble sugar contents were highest in plantlets cultured under red LED light. Our results showed that larger, healthier plantlets and a greater biomass of upland cotton were produced in the presence of red LED supplemented with a quantity of blue LED light. Blue and red LED (B:R = 1:1) was the most suitable light for the growth of upland cotton plantlets in vitro, and it may be used as alternative light source for an upland cotton culture system.     

Effect of temperature and various nitrogen sources on L(+)-lactic acid production by Lactobacillus casei

 Two homofermentative strains, Lactobacillus casei NRRL B-441 and Lactobacillus casei subsp. rhamnosus NRRL B-445 were selected for further study from 17 lactic acid bacterial strains screened for lactic acid production. The effect of temperature on lactic acid production with the selected strains was investigated by adapting both strains to four different temperatures. The production of L(+)-lactic acid by both strains was most efficient at 37°C, although with L. casei the highest lactic acid concentration was obtained at 41°C. The maximal volumetric productivity with L. casei was 4.1 g l^-1 h^-1 and with L. casei subsp. rhamnosus 3.5 g l^-1 h^-1. The composition of the medium was studied in order to replace the costly yeast extract with less expensive sources of nitrogen and amino acids. From 11 different nitrogen sources investigated at 37°C, barley malt sprouts (88 g l^-1 lactic acid in 66 h) and grass extract (74 g l^-1 lactic acid in 73 h) were the best economic alternatives. The effect of different combinations of yeast extract, peptone and malt sprouts was further studied by using statistical experimental design, and an empirical second-order polynomial model was constructed on the basis of the results. With the right combination most of the yeast extract could be substituted by barley malt sprouts for efficient lactic acid production. A method for extraction of nutrients and growth factors from malt sprouts is also described. Received: 25 September 1995/Accepted: 24 October 1995     

Change in the reaction of the antioxidant system of wheat sprouts after UV-irradiation of seeds

The response of the antioxidant system of sprouts of wheat Triticum aestivum L. to preliminary irradiation of seeds with UV light was studied. The dependence of lipid peroxidation and the extent of antioxidant activity on the duration of irradiation was studied. It was shown that low doses of UV radiation (5-15 min) stimulate the antioxidant protection of green wheat sprouts grown for eight days. Increasing the irradiation time to 30-60 min leads to the inhibition of lipid peroxidation by the antioxidant system. A more prolonged irradiation of seeds with UV light (for 1-6 h) led to an increase in the level of lipid peroxidation in sprouts. However, 1-2-day-old sprouts from seeds irradiated for 5-6 h, adapted themselves to the influence due to the compensatory mechanisms. By the 8th day of germination of preliminarily irradiated seeds, the content of antioxidants and malone dialdehyde returned to the norm. The dynamics of activity of peroxidase in seeds irradiated with low doses of UV light for 30 min was studied. It was found that on the third day of seed germination, a decrease in peroxidase activity followed by its slight increase occurred. The maximum activity of the enzyme in the endosperm was observed on day 5-6, and in roots and green sprouts, on day 3-5 of germination. It was concluded that antioxidants and peroxidase are involved in the compensatory mechanisms of inhibition of free radicals formed upon UV irradiation of seeds.     

Mechanisms of plant regeneration during succession after shifting cultivation in eastern Amazonia

The role of seed bank, seed rain, and regeneration from seedlings and sprouts after swidden agriculture was compared in 5-, 10- and 20-year-old secondary forest and in a primary forest in Bragantina, Pará, Brazil. The seed bank (0–5 cm soil depth) was largest in the 5-year-old forest (1190 ± 284 seeds m⁻²) and decreased nearly ten-fold with age to 137 ± 19 seeds m⁻² in the primary forest. The highest seed rain was in the 5-year-old forest (883 ± 230 seeds m⁻² year⁻¹) and the least in the primary forest (220 ± 80 seeds m⁻² year⁻¹). Large plants (≥5 cm dbh) had more individuals and species that regenerated from sprouts than from seeds and the most abundant tree species in the secondary forest stands of all ages appear to be maintained by sprouting. The smaller individuals (≥1 m tall, <5 cm dbh) in the 5-year-old forest were mainly from sprouts, but those in the older secondary forests originated mainly from seeds. These results show that at the beginning of succession, although many species can be introduced to swidden fallow from seed bank and seed rain, it is the sprout that is the main source of recruits of primary forest species in secondary forests in Bragantina.     

Induction of free radicals in seeds by high intensive flashes and the relevant phosphorus metabolism in the seedling

Influence of high intensive flashes on the yield of free radicals in intact seeds and excised embryonic axis, endosperm, and seed coat, and its resulting effect on seedling growth, total biomass production and phosphorus metabolism in wheat (Triticum aeativum), vetch (Vicia sativa L.) and onion (Allium cepa L.) was studied. Free radicals (f.r.) were formed mainly in seed coat and not in the endosperm. Vetch seeds after irradiation had 20.76 X 10¹³ f.r. g^-1 dry intact seed and 17.30 X 10¹³ f.r. g^-1 dry seed coat. Excised seed coats exposed to irradiation also yielded 17.28 × 10¹³ f.r. g^-1 dry matter. High irradiance “white light” flashes induced more f.r. than a monochromatic one of the same photon content. Red (650 nm), farred (750 nm) and even infra-red (1100 nm) radiation did not initiated f.r. formation but resulted in their decay in samples irradiated earlier by “white”, blue and green parts of the spectrum. Blue irradiation of seeds led to the decrease in the length of shoots and roots in comparison to “white”, green and red irradiation but their biomass increased faster than in the seedlings obtained from non-irradiated or irradiated with “white” and green radiation. The quantity of total acid soluble phosphorus followed a sequence with respect to wavelength of radiation: 436 nm > 650 nm> > 540 nm > non-irradiated > 300–800 nm. Quantity of inorganic phosphorus remained unaffected by different spectral character of radiation. The quantity of organic acid soluble nucleic phosphorus and acid insoluble polyphosphates was higher in samples irradiated with red beams (650 ± 6 nm).     

High frequency <Emphasis Type="Italic">in vitro</Emphasis> propagation of <Emphasis Type="Italic">Holarrhena antidysenterica</Emphasis> from nodal buds of mature tree

An in vitro method for propagation of Holarrhena antidysenterica Wall. has been developed using nodal explants from mature trees growing in the field. Irrespective of concentrations and combinations of growth regulators used, the axillary and terminal buds sprouted and elongated when inoculated on Murashige and Skoog (MS) medium. The highest numbers of shoots were formed when sprouted shoots were subcultured from MS basal medium onto MS medium containing 2 mg dm⁻³ N⁶-benzyladenine (BA) and 0.5 mg dm⁻³ α-naphthalene acetic acid (NAA). The shoot number further increased upon subculture on MS medium containing 0.5 mg dm⁻³ BA. By repeated sub-culturing of shoots derived from nodal axillary buds, a high frequency multiplication rate was established. The elongated shoots were excised and rooted in auxin free MS basal medium. Ex vitro rooting of in vitro formed shoots was achieved upon dipping the microshoots for 2 min in 2 mg dm⁻³ of indole-3-butyric acid solution. Successful field establishment and high (80–90 %) survival of plants was observed.     

Potato Seed-tuber Age Affects Mobilization of Carbohydrate Reserves During Plant Establishment

During the early stages of growth, developing sprouts rely heavilyupon tuber carbohydrate reserves. Strong sprouts are producedfrom young potato (Solaman tuberosum L.) seed-tubers, whereastubers of advanced physiological age produce sprouts with reducedvigour. Single-eye seedcores from 7- and 19-month-old seed-tuberswere sprouted in order to study the effect of tuber age on carbohydratereserve mobilization. Following 24 d of growth, the same amountof total shoot dry matter was produced from both ages of seedcores.However, d. wt of individual shoots from older seedcores was93 % lower than that from younger cores, reflecting a significantloss in apical dominance with age. Furthermore, core d. wt lossper unit gain in plant d. wt was greater from 19-month-old seedcores,indicating an age-related decrease in the efficiency of reservemobilization over the growth interval. During sprouting, ratesof starch hydrolysis and subsequent increases in total solublecarbohydrates were similar for both tuber ages. Reducing sugars(mg g d. wt^–1) accumulated faster in older than in youngercores; non-reducing sugars (mainly sucrose) decreased 53% inolder seedcores over the 24 d growth interval. Non-reducingsugar content (mg g d. wt^–1, mg core^–1) of youngercores remained constant. The results suggest that older coresare either less efficient at converting glucose to sucrose (themain translocatable carbohydrate in potatoes) or have higherrates of sucrose hydrolysis (e.g. increased invertase activity)compared with younger tuber tissues during sprouting Potatoes (Solanum tuberosum L.), seed-tuber age, carbohydrate mobilization, plant growth potential     

Contribution of Oxidative Stress to the Development of Cold-Induced Damage to Leaves of Chilling-Sensitive Plants: 2. The Activity of Antioxidant Enzymes during Plant Chilling

Changes in the activities of cytosolic superoxide dismutase, ascorbate peroxidase, and catalase were studied in 7–11-day-old seedlings of maize (Zea mays L.), cucumber (Cucumis sativus L.), millet (Panicum miliaceum L.), and etiolated potato (Solanum tuberosum L.) sprouts. The assays were performed immediately after chilling at 2°C for 1–24 h and one day after 24-h chilling. During the first 1–2 h of chilling, enzyme activities were substantially reduced in chilling-sensitive plants (cucumber and maize). Further chilling resulted in a gradual increase in the enzyme activities to a degree dependent on plant species. One day after the plants were returned to a high temperature, the enzyme activities were restored to an initial level or exceeded it (excluding maize superoxide dismutase). In the potato (cold-resistant species), we did not observe any regular changes in the activities of antioxidant enzymes. On the whole, the activities of these enzymes inversely depended on species cold-resistance. The conclusion is that one of the cold-resistance factors is the capacity of antioxidant enzymes to maintain their activities during chilling and restore them relatively rapidly after plant transfer to warm conditions.     

CO2 and light effects on deciduous trees: growth, foliar chemistry, and insect performance

This study examined the effects of CO₂ and light availability on sapling growth and foliar chemistry, and consequences for insect performance. Quaking aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), and sugar maple (Acer saccharum Marsh.) were grown in controlled environment greenhouses under ambient or elevated CO₂ (38.7 and 69.6 Pa), and low or high light availability (375 and 855 μmol m⁻² s⁻¹). Because CO₂ and light are both required for carbon assimilation, the levels of these two resources are expected to have strong interactive effects on tree growth and secondary metabolism. Results from this study support that prediction, indicating that the relative effect of rising atmospheric CO₂ concentrations on the growth and secondary metabolism of deciduous trees may be dependent on light environment. Trees in ambient CO₂-low light environments had substantial levels of phytochemicals despite low growth rates; the concept of basal secondary metabolism is proposed to explain allocation to secondary metabolites under growth-limiting conditions. Differences between CO₂ and light effects on the responses of growth and secondary metabolite levels suggest that relative allocation is not dependent solely on the amount of carbon assimilated. The relative growth rates and indices of feeding efficiency for gypsy moth (Lymantria dispar L.) larvae fed foliage from the experimental treatments showed no significant interactive effects of light and CO₂, although some main effects and many host species interactions were significant. Gypsy moth performance was negatively correlated with CO₂- and light-induced increases in the phenolic glycoside content of aspen foliage. Insects were not strongly affected, however, by treatment differences in the nutritional and secondary chemical components of birch and maple. Received: 15 July 1998 / Accepted: 23 December 1998     

Lipases in the storage tissues of peanut and other oil seeds during germination

The castor-bean endosperm-the best-studied material of reserve lipid hydrolysis in seed germination-was previously shown to have an acid lipase and an alkaline lipase having reciprocal patterns of development during germination. We studied oil seeds from 7 species, namely castor bean (Ricinus communis L.), peanut (Arachis hypogaea L.), sunflower (Helianthus annus L.), cucumber (Cucumis sativus L.), cotton (Gossypisum hirsutum L.), corn (Zea mays. L.) and tomato (Lycopersicon esculentum Mill.). The storage tissues of all these oil seeds except castor bean contained only alkaline lipase activity which increased drastically during germination. The pattern of acid and alkaline lipases in castor bean does not seem to be common in other oil seeds. The alkaline lipase of peanut cotyledons was chosen for further study. On sucrose gradient centrifugation of cotyledon homogenate from 3-d-old seedlings, about 60% of the activity of the enzyme was found to be associated with the glyoxysomes, 15% with the mitochondria, and 25% with a membrane fraction at a density of 1.12 g cm^-3. The glyoxysomal lipase was associated with the organelle membrane, and hydrolyzed only monoglyceride whereas the mitochondrial and membrane-fraction enzymes degraded mono-, di- and triglycerides equally well. Thus, although the lipase in the glyoxysomes had the highest activity, it had to cooperate with lipases in other cellular compartments for the complete hydrolysis of reserve triglycerides.     

In vitro propagation of the endangered orchid Laelia speciosa

Laelia speciosa is an endangered epiphytic orchid. The effects of various media components on germination of L. speciosa were evaluated. Pods were collected at 4, 7, and 9 months following hand-pollination, and seeds were germinated on Murashige and Skoog (MS) media with 30 g l⁻¹ sucrose and five concentrations (0.0, 0.04, 0.22, 0.44, and 2.22 μM) of benzyladenine (BA) under light and dark conditions. Gibberellic acid (GA₃; 0.0, 0.29, 1.44, 2.89, 14. 43 and 28.87 μM) with naphthaleneacetic acid (NAA; 0.0, 0.54, 1.34, 2.69, and 5.37 μM) were evaluated for in vitro subcultivation. MS medium with 30 g l⁻¹ sucrose was effective for germination. The effects of BA and light on germination of L. speciosa seeds differed with pod maturity. All mature seeds germinated using 0.44 μM BA and light. The highest frequency of germinated seedlings (60%) was obtained using mature seeds grown on MS medium without BA and under light conditions. For subculture, MS with 30 g l⁻¹ sucrose, 2.69 μM NAA, and 0.29 μM GA₃ was effective. Plantlets of 5 cm in length were transplanted to the greenhouse, and a 77.5% of survival rate was obtained. A successful protocol for micropropagation by seed germination will contribute to the development of a sustainable management program for L. speciosa.     

Effects of long-term storage on phytochrome-mediated germination in lettuce seeds

The effects of long-term seed storage on the physiological properties of phytochrome-mediated germination including water uptake, the temperature and light flunnce dependencies of germination and dark germination were studied. The fluenceresponse relationships of the brief irradiation with monochromatic red (660 nm, 7.5 W m⁻²) and far-red (750 nm, 6.6 W m⁻²) light at various times after sowing were also studied. The samples used consisted of three lots of seeds ofLactuca sativa L. cv. MSU-16, which had been harvested in 1976, 1979 and 1985 and stored dry for 9, 6 and 0 years, respectively, in darkness at 23±2 C until the experiments were carried out in July–August, 1985. Seeds with the longer storage periods showed the higher ability to germinate in both continuous darkness and continuous white fluorescent light at 20–30 C. In the seeds stored for 6 or 9 years, red light irradiation for 20 sec given at 15 min or more after sowing at 25 C induced as high a percent germination (85–95%) as those under continuous white fluorescent light. In the freshly harvested seeds, however, germination under continuous white fluorescent light (46%) was considerably lower than the germination induced by the red pulse (97%). Germination of the seeds decreased when the intervals between sowing and a far-red irradiation for 20 sec increased up to 100 min (or 30 min in the freshly harvested seeds). The far-red pulse given later than 100 min (or 6 hr in the freshly harvested seeds) after sowing resulted in an increased germination up to the dark-germination levels with increasing intervals between sowing and the pulse irradiation. Before or at 3 min after sowing, the seeds stored for 6 or 9 years were responsive to the far-red pulse although they were not or hardly responsive to the red pulse, while the freshly harvested seeds were responsive to both the far-red and the red pulses. These data indicate that normal functions of phytochrome completely survived in the dry seeds during storage at 25 C for as long as 6 or 9 years and that these functions are restored into full operation by means of imbibition. The differences in the dependence of germination on the time and fluence of a single pulse of red or far-red light seems to be related to the smaller water content throughout the imbibition in the seeds with the longer storage periods. The greater ability to germinate in the dark indicates the greater amounts of P_FR or the greater responsivity to P_FR, in the seeds with the longer storage periods.