Tracking paleoenvironmental changes in coralline algal-dominated carbonates of the Lower Oligocene Calcareniti di Castelgomberto formation (Monti Berici, Italy)

Lower Oligocene, shallow-water carbonates of the Calcareniti di Castelgomberto formation (Monti Berici, Italy, Southern Alps) are studied in detail with respect to fabric and component distributions in order to trace paleoecological changes along a monotonous sedimentary stacking pattern. The carbonates are dominated by coralline algal rudstones with a packstone to wackestone matrix. Non-geniculate coralline algae include six genera: Lithoporella melobesioides, Mesophyllum, Neogoniolithon, Spongites, Sporolithon, and Subterraniphyllum. The algae are found in the form of encrusting thalli, rhodoliths, and coralline debris. Non-algal components include larger, small benthic, and planktonic foraminifera associated with bryozoans, zooxanthellate corals, and echinoderms. Four carbonate facies are distinguished: (1) coralline algal facies, (2) coralline algal-coral facies, (3) coralline algal-larger foraminiferal facies, and (4) coralline algal debris facies. Marly horizons also occur in the section. The facies and coralline algal content are interpreted with respect to light intensity, hydrodynamic energy, biotic interactions, and substrate stability. Facies development along the studied section shows systematic variations, suggesting asymmetric sea-level changes with rapid regressions and gradual transgressions.     

Feeding preferences of the sandhopper Orchestoidea tuberculata: the importance of algal traits

Factors such as nutritional quality and the secondary metabolite content of food resources have been shown to influence the feeding behavior of herbivores in many marine habitats. For intertidal macroalgae consumers on sandy beaches, the influence of these factors on feeding behavior and the consequences on their performance is poorly understood. In this study, we evaluated the relationships of nutritional quality, chemical defenses (phlorotannins), and the structure of three macroalgal species that form the bulk of imported wrack subsidies to beaches in southern Chile, with the feeding behavior, absorption efficiency, and growth rate of the talitrid amphipod Orchestoidea tuberculata, one of the most abundant organisms in this environment. The amphipods preferred Durvillaea antarctica over Lessonia nigrescens and Macrocystis pyrifera when simultaneously offered fresh pieces of each alga. Similar results were observed when artificial food made of dry powdered algae of each species was provided, suggesting that the structure of these three algae did not influence preference. The performance of amphipods when reared on a diet of a single algal species matched feeding preferences; higher growth rates were observed in treatments with the preferred alga, D. antarctica. These results imply that D. antarctica is a superior food item for O. tuberculata when compared to L. nigrescens or M. pyrifera, and also that the alga’s intrinsic quality (i.e., not structure) may influence dietary preference in these consumers. The higher content of proteins and carbohydrates found in D. antarctica may explain why this macroalga represents better quality food for O. tuberculata. Phlorotannin content did not have obvious negative effects on diet choice or growth, as D. antarctica, the alga with greater content of these secondary metabolites, was preferred and associated with higher growth rates of O. tuberculata. However, it is necessary to emphasize that the low phlorotannins concentrations registered in the three macroalgae species examined in this study, may not have been sufficient to deter O. tuberculata. When the amphipods were fed with each alga individually, they consumed significantly higher quantities of D. antarctica, which suggests that O. tuberculata did not eat more to compensate for the lower nutritional quality of the other algal species in order to maintain growth. Nor was compensation for lower food quality achieved by increasing absorption efficiency. Our results imply that the composition of the macroalgae arriving on the beach can significantly affect the performance and subsequent life history traits of O. tuberculata and by extension other amphipod species.     

Isolation and identification of a plant growth inhibitor from Tinospora tuberculata Beumee

Tinospora tuberculata Beumee has been used widely as a folk medicine and several bioactive compounds have been isolated. However, no herbicidal compound has been reported in this species. Therefore, we investigated the presence of phytotoxins in T. tuberculata. The aqueous methanol extracts of T. tuberculata inhibited the growth of roots and shoots of cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), timothy (Phleum pratense L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). The extract was then purified by several chromatographic runs with monitoring the inhibitory activity and the main phytotoxic substance was isolated. The chemical structure of the compound was determined by spectral data as syringin (4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2,6-dimethoxyphenyl β-d-glucopyranoside). It inhibited the root and shoot growth of all test plant species at concentrations >10 µM. The concentrations required for 50 % inhibition of root and shoot growth of cress and lettuce ranged from 78.2 to 412 μM, and that of timothy and barnyard grass renged from 9.8 to 73.2 µM. Effectiveness of syringin on monocotyledonous (timothy and barnyard grass) plants was greater than that on dicotyledonous (cress and lettuce) plants. These results suggest that syringin may contribute to the allelopathic effect caused by the T. tuberculata extract.     

Predicting Production in Light-Limited Continuous Cultures of Algae

Equations relating productivity, growth rate, cell concentration, and light absorption lead to the prediction that, when incident light is below saturating intensity, maximal productivity will occur at half the maximal growth rate. The freshwater alga Chlorella pyrenoidosa TX71105 and the marine alga Dunaliella tertiolecta were grown in a small continuous culture apparatus with turbidostatic control. With both cultures, the cell concentration showed a linear decrease with dilution rate. Productivity was maximal at about one-half the maximal dilution rate. Average mass per cell increased near the maximal dilution rate, causing some asymmetry in the productivity versus dilution rate curve. The chlorophyll content per unit mass decreased in this region, but the chlorophyll content per cell remained constant. Best production rate in a light-limited algal culture was obtained when the growth rate at very low cell concentration was determined in the apparatus and the dilution rate was set at one-half that value.     

Extract powder from the brown alga Ascophyllum nodosum (Linnaeus) Le Jolis (AMPEP): a “vaccine-like” effect on Kappaphycus alvarezii (Doty) Doty ex P.C. Silva

The benefits of using Acadian Marine Plant Extract Powder (AMPEP), obtained from the brown algae Ascophyllum nodosum, for improving growth of the red alga Kappaphycus alvarezii has been demonstrated by authors in the Philippines and Brazil, particularly for increasing daily growth rate and mitigation of epiphytes. However, the processes which occur have not been discussed. This study examined in vitro the relationship between those red algal defense mechanisms and K. alvarezii responses using AMPEP treatments. The administration of the extract reduced the effects of the oxidative burst (production of hydrogen peroxide) which may be extremely aggressive for an individual and its epiphyte. The bleaching of the non-corticated portions of Polysiphonia subtilissima thalli that were cultivated as simulated epiphytes with AMPEP samples confirmed that the reaction was evident in which AMPEP protected K. alvarezii from the hydrogen peroxide effects. It is proposed that the use of the brown seaweed powder AMPEP acts as a potential vaccine, eliciting activation of the red seaweed K. alvarezii natural defenses against pathogens and ameliorating the negative effects of long-term exposure to oxidative bursts.     

Growth but Not Photosynthesis Response of a Host Plant to Infection by a Holoparasitic Plant Depends on Nitrogen Supply

Parasitic plants can adversely influence the growth of their hosts by removing resources and by affecting photosynthesis. Such negative effects depend on resource availability. However, at varied resource levels, to what extent the negative effects on growth are attributed to the effects on photosynthesis has not been well elucidated. Here, we examined the influence of nitrogen supply on the growth and photosynthesis responses of the host plant Mikania micrantha to infection by the holoparasite Cuscuta campestris by focusing on the interaction of nitrogen and infection. Mikania micrantha plants fertilized at 0.2, 1 and 5 mM nitrate were grown with and without C. campestris infection. We observed that the infection significantly reduced M. micrantha growth at each nitrate fertilization and more severely at low than at high nitrate. Such alleviation at high nitrate was largely attributed to a stronger influence of infection on root biomass at low than at high nitrate fertilization. However, although C. campestris altered allometry and inhibited host photosynthesis, the magnitude of the effects was independent of nitrate fertilizations. The infection reduced light saturation point, net photosynthesis at saturating irradiances, apparent quantum yield, CO₂ saturated rate of photosynthesis, carboxylation efficiency, the maximum carboxylation rate of Rubisco, and maximum light-saturated rate of electron transport_, and increased light compensation point in host leaves similarly across nitrate levels, corresponding to a similar magnitude of negative effects of the parasite on host leaf soluble protein and Rubisco concentrations, photosynthetic nitrogen use efficiency and stomatal conductance across nitrate concentrations. Thus, the more severe inhibition in host growth at low than at high nitrate supplies cannot be attributed to a greater parasite-induced reduction in host photosynthesis, but the result of a higher proportion of host resources transferred to the parasite at low than at high nitrate levels.     

EFFECTS OF THE SYMBIOTIC RED ALGA HYPNEOCOLAX STELLARIS ON ITS HOST HYPNEA MUSCIFORMIS (HYPNEACEAE,GIGARTINALES)1

The presence of the “symbiotic” red alga Hypneocolax stellaris Borgesen was found to substantially reduce the growth rate of Hypnea musciformis (Wulfen) Lamouroux. The growth rate of injected field material was 40% less than unifected thalli. Likewise, the growth rate of host thalli infected in the laboratory was reduced 70% compared to uninfected thalli. Neither the quantity nor quality of carrageenan extracted from Hypnea musciformis was directly affected by the presence of Hypneocolax stellaris. In a mariculture system the presence of a symbiotic alga on its host would be expected to reduce the host's growth rate and thereby lower its economic potential.     

First report of Melanoides tuberculata (Mollusca: Thiaridae) harboring a xiphidiocercaria in Brazil: A new parasite introduced in the Americas?

Xiphidiocercariae were found in the invasive snail Melanoides tuberculata collected during a malacological survey in Ceará-Mirim, State of Rio Grande do Norte, Northeastern Brazil in November 2018 and submitted to morphological and molecular analyses. The morphology revealed similarities between the larvae here reported for the first time in M. tuberculata from Brazil and other xiphidiocercariae described in thiarid snails from Asia and Africa. Phylogenetic analyses based on 28S and ITS-2 sequences revealed that the larvae correspond to an unidentified species of the family Lecithodendriidae. Aspects related to the morphology and taxonomy of xiphidiocercariae found in M. tuberculata are briefly discussed. It is possible that the parasite here reported is a newly introduced species transmitted by M. tuberculata in the American continent.     

Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore

Factors determining the degree of dietary generalism versus specialism are central in ecology. Species that are generalists at the population level may in fact be composed of specialized individuals. The optimal diet theory assumes that individuals choose diets that maximize fitness, and individual specialization may occur if individuals'' ability to locate, recognize, and handle different food types differ. We investigate if individuals of the marine herbivorous slug Elysia viridis, which co-occur at different densities on several green macroalgal species in the field, are specialized to different algal hosts. Individual slugs were collected from three original algal host species (Cladophora sericea, Cladophora rupestris and Codium fragile) in the field, and short-term habitat choice and consumption, as well as long-term growth (proxy for fitness), on four algal diet species (the original algal host species and Chaetomorpha melagonium) were studied in laboratory experiments. Nutritional (protein, nitrogen, and carbon content) and morphological (dry weight, and cell/utricle volume) algal traits were also measured to investigate if they correlated with the growth value of the different algal diets. E. viridis individuals tended to choose and consume algal species that were similar to their original algal host. Long-term growth of E. viridis, however, was mostly independent of original algal host, as all individuals reached a larger size on the non-host C. melagonium. E. viridis growth was positively correlated to algal cell/utricle volume but not to any of the other measured algal traits. Because E. viridis feeds by piercing individual algal cells, the results indicate that slugs may receive more cytoplasm, and thus more energy per unit time, on algal species with large cells/utricles. We conclude that E. viridis individuals are specialized on different hosts, but host choice in natural E. viridis populations is not determined by the energetic value of seaweed diets as predicted by the ODT.     

How do two specialist butterflies determine growth and biomass of a shared host plant?

Although insect herbivory can modify subsequent quantity and quality of their host plants, change in plant quantity following herbivory has received less attention than plant quality. In particular, little is known about how previous herbivore damage determines plant growth and biomass in an insect species-specific manner. We explored whether herbivore species-specific food demand influences plant growth and biomass. To do this, we conducted a series of experiments and field survey using two specialist butterflies, Sericinus montela and Atrophaneura alcinous, and their host plant, Aristolochia debilis. It is known that A. alcinous larva requires four times more food resources to fulfill its development than S. montela larva. Despite that A. alcinous larvae imposed greater damage on plants than S. montela larvae, plant growth did not differ due to herbivory by these species both in single and multiple herbivory events. On the other hand, total aboveground biomass of the plants was reduced more by A. alcinous than S. montela feeding regardless of the number of herbivory events. Feeding on plants with a history of previous herbivory neither decreased nor increased larval growth. Our results suggest that food demand of the two butterfly species determined subsequent plant biomass, although the plant response may depend on tolerance of the host plant (i.e., ability to compensate for herbivore damage). Such difference in the effects of different herbivore species on host plant biomass is more likely to occur than previously thought, because food demand differs in most herbivore species sharing a host plant.     

Comparative studies on the nutrition of two species of abalone,Haliotis tuberculata Linnaeus and Haliotis discus hannai Ino I. Effects of algal diets on growth and biochemical composition

Summary

This study was conducted to examine the nutritional value of eight algal diets for two species of abalone, Haliotis tuberculata and Haliotis discus hannai, by measuring biochemical composition of the algae and relating this to feeding rate, growth and biochemical composition of the animals. Nutritional value of algal diets can be divided into three categories for each species of abalone. For H. tuberculata the best performance was on the mixed diet and Palmaria palmata intermediate was Alaria esculenta, Ulva lactuca and Laminaria digitata, and lowest growth was on Laminaria saccharina and Chondrus crispus. For H. discus hannai, best performance was on A. esculenta, P. palmata and the mixed diet; intermediate was on L. saccharina and L. digitata and lowest was on U. lactuca. It is generally accepted that high “balanced” levels of protein (>15%), lipid (3–5%) and carbohydrate (20–30%), with no detrimental substances in natural algae are essential for optimal growth performance of these abalone. The fact that A. esculenta, L. saccharina and U. lactuca had different dietary values for the two abalone species indicates specific nutritive requirements and/or digestive physiology. Overall, H. tuberculata grew faster, had higher food conversion efficiencies and muscle yield than H. discus hannai. Generally abalone fed on the highest category diets, had higher muscle yields and levels of protein, visceral lipids and muscle carbohydrate. Viscera and foot muscle are reservoirs for lipid and carbohydrate, respectively. The effect of algal diet on sexual maturation is similar to that on somatic growth.     

Artificial mussels as indicators of metal pollution in freshwater systems: A field evaluation in the Koekemoer Spruit,South Africa

There has been a recent increase in water quality problems in South Africa. The monitoring of water resources is important for the continued management of water resources. The use of artificial mussels (AMs) as passive sampling devices in the monitoring of metals within a freshwater system was evaluated in a recent field study. Correlation testing was conducted between the AMs and Melanoides tuberculata for As, Cd, Cr, Co, Cu, Pb, Mn, Ni, U, V and Zn. It was found that a positive significant correlation exists between AMs and M. tuberculata with regards to As, U, and Co accumulations. The trend of metal accumulation between AMs and M. tuberculata were found to be similar for all of the metals tested. Site 2 which is located close to a gold mine, was found to have the highest metal concentrations in this study. This study confirms the hypothesis that AMs can be used as a useful tool for monitoring metals in freshwater.     

The impact of Dictyota spp. on Halimeda populations of Conch Reef, Florida Keys

Species of the brown alga Dictyota dominate the reef tract in the Florida Keys. In surveys during summer and fall months between 1994 and 2001, Dictyota occupied as much as 70% of the benthos on Conch Reef. Dictyota spp. were found growing epiphytically on Halimeda tuna, Halimeda opuntia, Lobophora variegata, Galaxura sp., fire coral, hard corals, soft corals, bryozoans and a variety of sponges on Conch Reef. From 1994 to 2001, the percent coverage of Halimeda spp. declined from 15% to 3% on the same reef. In Aug. 1999, 2000 and 2001, on average, 56% of two Halimeda species on Conch Reef had >50% of their thalli covered by Dictyota menstrualis and Dictyota pulchella. To address the impact of Dictyota on Halimeda, short-term growth of unepiphytized and heavily epiphytized (>50% Dictyota cover) H. tuna were compared with unepiphytized H. tuna to which a Dictyota mimic was attached. The number of new segments per plant ranged from 1 to 174 over 9 days. Halimeda thalli with >50% Dicytota cover and thalli covered with Dictyota mimic grew significantly slower than unepiphytized thalli. A second short-term experiment addressed the impact of neighboring Dictyota on the growth and metabolism of unepiphytized H. tuna. Augmenting or clearing epilithic Dictyota around but not in contact with H. tuna had no impact on growth or metabolism of H. tuna. Unepiphytized and heavily epiphytized H. tuna were also collected for studies of metabolism. This work indicated that epiphytic Dictyota negatively impacts metabolic rates of H. tuna in part by shading H. tuna thalli. This negative impact was also in part chemically mediated, as exposure to Dictyota-conditioned water elevated respiration rates in the same manner as seen in the metabolic studies of naturally epiphytized H. tuna.     

Non-calcified macroalgae from the lower Famennian (Upper Devonian) of the Holy Cross Mountains,Poland

Non-calcified algal remains were collected from the lower Famennian deposits at the Kowala quarry in the Holy Cross Mountains, central Poland. Each specimen is represented solely by vegetative organs. On the basis of the material collected, a new algal genus and species has been formally erected. Vittella dixii nov. gen., nov. sp. (Order ?Bryopsidales) includes thalli consisting of long bundles of hair-like filament structures arranged in parallel fashion to the thallus length. Some other algal remains are regarded as Inocaulis-like forms. They possess long, flat blades with entire margins, and are ornamented with very dense, hair-like projections. The rest of the specimens found so far has been illustrated and tentatively classified as probably belonging to either Bryopsidales or Dasycladales algae. The exceptional preservation of the non-calcified algal thalli investigated suggests that special taphonomic conditions have prevailed during sedimentation of the lower part of the Famennian Kowala section. These may have involved rather rapid burial in oxygen-restricted (dysoxic and anoxic) sea-bottom environment, inhibiting the activities of scavengers and bioturbators, as well as oxidative degradation. The preservation of the algae, together with sedimentological and geochemical characteristics of the host rocks indicate that they rather represent parautochthonous assemblage, buried close to their natural habitat.     

A SIMPLE METHOD FOR ISOLATING FILAMENTS AS “ALGAL SEED STOCK” FROM MONOSTROMA LATISSIMUM (CHLOROPHYTA) GERMLINGS,AND APPLICATION FOR MASS CULTIVATION1

Germlings were grown from Monostroma latissimum Wittr. reproductive cells on nylon ropes. Holdfast threads and some uniseriate filaments were observed to have penetrated the fibers of the dispersed ropes. The algal filaments were easily isolated and prepared for cultivation, in comparison to the methods of enzymatically isolated algal protoplasts. Under low light (60–100 μmol photons · m^?2 · s^?1), the algal filaments grew to form a filamentous mass. When cultivated under stronger light (300–600 μmol photons · m^?2 · s^?1), they grew to initially form tubular thalli and then, when cultivated under light intensities >700 μmol photons · m^?2 · s^?1, formed foliaceous thalli. Consequently, the filaments were homogenized into small sections and then sewed on the nylon rope for algal mass cultivation. Under high‐intensity natural light, they grew to form leafy thalli.     

Sediments influence accumulation of two macroalgal species through novel but differing interactions with nutrients and herbivory

Despite increasing concern that sediment loads from disturbed watersheds facilitate algal dominance on tropical reefs, little is known of how sediments interact with two primary drivers of algal communities, nutrients and herbivory. We examined the effects of sediment loads on the thalli of two increasingly abundant genera of macroalgae, Galaxaura and Padina, in a bay subject to terrestrial sediment influx in Mo’orea, French Polynesia. Field experiments examining (1) overall effects of ambient sediments and (2) interacting effects of sediments (ambient/removal) and herbivores (caged/uncaged) demonstrated that sediments had strong but opposite effects on both species’ biomass accumulation. Sediment removal increased accumulation of Padina boryana Thivy 50% in the initial field experiment but had no effect in the second; rather, in a novel interaction, herbivores overcompensated for increases in tissue nutrient stores that occurred with sediments loads, likely by preferential consumption of nutrient-rich meristematic tissues. Despite negative effects of sediments on biomass, Padina maintained rapid growth across treatments in both experiments. In contrast, positive growth in Galaxaura divaricata Kjellman only occurred with ambient sediment loads. In mesocosm experiments testing interactions of added nutrients and sediments on growth, Galaxaura grew at equivalent rates with sediments (collected from thalli on the reef) as with additions of nitrate and phosphate, suggesting sediments provide a nutrient subsidy. For Padina, however, the only effect was a 50% reduction in growth with sediment. Overall, retention of thallus sediments creates a positive feedback that Galaxaura appears to require to sustain net growth, while Padina merely tolerates sediments. These results indicate that sediments can modify nutrient and herbivore control of algae in ways that differ among species, with the potential for strong and unexpected effects on the abundance and composition of tropical reef macroalgae.     

Study of photosynthetic characteristics of the Pyropia yezoensis thallus during the cultivation process

The photosynthetic characteristics of thalli of cultured Pyropia yezoensis strains collected in January, February, and March in seaweed cultivation area of South China Yellow Sea were studied. Results showed that the maximum quantum efficiency (F _v/F _m) of all P. yezoensis thallus collected at different times was 0.65. The actual quantum efficiency (ΔF/F _m′) of samples in January was the lowest of all samples, while the ΔF/F _m′ of samples in March was significantly higher than those in January and February. The increase of temperature and photosynthetic pigments ratios of phycoerythrin and chlorophyll a (PE/Chla) and phycocyanin and chlorophyll a (PC/Chla) from January to March may be the important reasons for the increase in light use efficiency of thallus; although the thallus in March was significantly thicker than in January which may have reduced the light energy absorbed by photosynthetic pigments, the increase of relative high energy use efficiency also helped to maintain the photosynthetic oxygen evolution rate in March. The thicker thallus also reduced photodamage, and the thallus area was increased obviously in March, so the growth rate of thallus in March was over 35 % higher than that in February. Our research indicates that the photosynthetic characteristics of P. yezoensis strains thalli have a close relationship with their growth stage and environmental factors especially temperature, and those photosynthetic characteristics are also reflected in the growth rate of the thalli.     

Fitness consequences of host plant choice: a field experiment

Determining the relative contributions of different ecological factors for herbivore fitness is one key to understanding the ecology and evolution of host plant choice by herbivores. Natural enemies are increasingly being recognized as an important factor: host plants of inferior quality for development may still be used by herbivores if they provide enemy‐free space (EFS). Here we used the tobacco hornworm, Manduca sexta, to experimentally disentangle the effects of natural enemies from the potentially confounding factors of host plant quality, competition and microhabitat. We explored the consequences for both individual components of fitness and total fitness of M. sexta feeding on a typical high quality host plant, tobacco Nicotiana tabacum and a novel, low quality host plant, devil's claw Proboscidea louisianica in an experimental field environment in the presence of a parasitoid natural enemy, Cotesia congregata. Although early larval survival, development and growth rates, final body size and fecundity were all reduced for M. sexta feeding on devil's claw, a high rate of parasitism on tobacco and an absence of parasitism on devil's claw contributed to similar total fitness (net reproductive rate, R₀) across the two host plant species. Our results suggest M. sexta has adopted a novel host plant (devil's claw) outside its typical host range because this host plant provides enemy free space. In addition, oviposition behavior of adult female M. sexta appears to be well suited to exploiting the enemy‐free space on devil's claw; oviposition by M. sexta on devil's claw appears to correspond with seasonal variation in parasitoid abundance.     

The reflectance properties of plant internodes modify elongation responses to lateral far-red radiation

The quality and quantity of light reflected from Nicotinia tabacum L. internodes was monitored as the angle of incidence was varied. Reflectance of incident light, which was either normal or longitudinal to the internode axis, was investigated. Increasing the angle of incidence caused a greater proportion of incident light to be reflected. Light striking N. tabacum internodes was always modified prior to reflection, and smaller incident angles produced greater modification of the reflected light quality. At larger angles, interactions with the internode were reduced. As a parallel investigation, the extension growth rate of light-grown Sinapis alba L. seedlings was monitored continuously using sensitive linear displacement transducers. When the angle of illumination by fibre-optic probes, presenting far-red light to the growing internode, was changed from 0° to 45°, an increase was observed in stem extension rate. There is a possibility that this rate increase was the result of a fall in the red:far-red ratio (R:FR) present inside the plant internode as the angle of incidence was altered. However, it is more likely that it was due to the larger surface area of stem being illuminated. The consequences of these observations are discussed in relation to the potential influence of such modified reflections on canopy light environments and resultant shade responses which may occur when light of known R:FR impinges on plant internodes at angles other than 0°. The possibility is discussed that plants may perceive the quality of reflected radiation from neighbouring plants to be substantially different dependent upon the angle at which it is reflected.     

不同光质及肥料浓度对小报春生长发育的影响

不同光质和肥料浓度对小报春(Primula forbesii)幼苗生长的影响进行了研究。结果表明:蓝光能促进小报春幼苗的光合速率和蒸腾速率,黄光能明显地促进小报春幼苗增高,红光则促进植株开花;肥料浓度EC 2.0 mS cm-1对促进小报春幼苗生长及叶面积增大的效果最佳;交互处理试验以红光/EC 2.0 mS cm-1的效果最明显,对小报春幼苗的营养生长和生殖生长均有促进作用。因此,选择合适的光质和肥料浓度有利于促进植物的生长发育。