Endophytic System Research Articles

Comparative haustorium morphology and vegetative reproduction in the Old World genus Scurrula L. (Loranthaceae) from the Central Nepal Himalayas

In a comparative morphological study of haustoria in the four Scurrula species occurring in the Annapurna Conservation Area (ACA) of Nepal, only one basic type of haustorium was found, regardless of host and elevation, namely a primary haustorium (leading to a wood rose) with epicortical root. The endophytic system of the primary haustorium, however, showed differences, which allowed classification into (1) flanging endophyte, (2) flanging endophyte with radial shaft, and (3) sinker endophyte. Scurrula elata and Scurrula gracilifolia showed marked differences in haustorium morphology on different hosts. Scurrula elata is most successful in establishing over a wide range of hosts due to its specific haustorium morphology and endophyte system. Epicortical roots of the genus Scurrula resemble those of other Old World Loranthaceae morphologically and functionally, but differ significantly from New World species. Vegetative reproduction by means of epicortical roots, which develop secondary haustoria and shoots, is very common in all four Scurrula species. The number of root-borne shoots produced by secondary haustoria varied among Scurrula species, depending on the age of the mistletoes as well as the length and vigour of the roots.

Using a multidisciplinary approach with undergraduate students to study the grass endophyte system

We have been collaborating on a multidisciplinary research programme with undergraduate (baccalaureate) students for the past 3 years, funded by the National Science Foundation in the USA. The project focuses on the ecological interaction between endophytic fungi and the grasses they inhabit and involves students (10-15 annually) and faculty (5 and 1 post-doc) from the departments of Biology, Chemistry and Mathematics. We briefly present some of our results from ongoing projects on stomatal conductance and photosynthetic rates in tall fescue, wound-induced responses at the molecular level, and modelling tri-trophic level interactions. We also discuss how we came together to initiate the project; challenges, pitfalls, and advantages of doing multidisciplinary, multi-investigator research with undergraduates. We will present our assessment results, which are focused on how students feel their involvement in multidisciplinary research differs from what it would be in disciplinary research. Keywords: Neotyphodium coenophialum, tall fescue, woundinduced response, tri-trophic interactions, water use efficicency, stomatal conductance, photosynthesis

Charting the Isophasic Endophyte of Dwarf Mistletoe Arceuthobium douglasii (Viscaceae) in Host Apical Buds

Dwarf mistletoes (Arceuthobium; Viscaceae) are highly specialized dioecious angiosperms parasitic on many gymnosperm hosts in the northern hemisphere. Several dwarf mistletoe species are capable of inducing an unusual form of isophasic infection in which the internal (endophytic) system proliferates even into the apical buds of its hosts. Studies of the internal endophytic system have, for the most part, focused on the parasite within secondary host tissues. The present anatomical and ultrastructural study characterizes the growth pattern of the isophasic endophytic system of Arceuthobium douglasii within the dormant apical buds of Pseudotsuga menziesii. Semi-thin serial sections from dwarf mistletoe-infected host apical buds were mounted, stained and micrographed. Graphic files were created from the serial micrographs and these files were stacked. These stacked files were utilized to describe the pattern of growth of the endophyte within the host tissue. The interface between cells of the mistletoe and host was also examined at the ultrastructural level by transmission electron microscopy. By utilizing a novel technique of superimposed graphics, the current study reveals an organized pattern of mistletoe distribution that penetrates further into host tissues than previously known. A consistent pattern of growth occurring even into the preformed leaves of the host is documented. The apparently non-intrusive growth of the parasite appears to be developmentally synchronized with that of the host. No symplastic connections were observed in the ultrastructural examination of the parasite/host interface within the apical buds of Pseudotsuga menziesii parasitized by A. douglasii or of Pinus contorta parasitized by A. americanum.

Seasonal synchrony of a green algal endophyte, Acrosiphonia (Codiolales), with its red algal hosts, Mastocarpus and Mazzaella (Gigartinales)

A.V. Sussmann, R. Scrosati and R.E. DeWreede. 2005. Seasonal synchrony of a green algal endophyte, Acrosiphonia (Codiolales), with its red algal hosts, Mastocarpus and Mazzaella (Gigartinales). Phycologia 44: 129–132.‘Codiolum’ and ‘chlorochytrium’ (both unicellular sporophyte phases of the filamentous green alga Acrosiphonia) are endophytic in the red algal crust ‘petrocelis’ (sporophyte of Mastocarpus papillatus) and in the bladed red alga Mazzaella splendens, respectively, in southern British Columbia, Canada. This study is the first to investigate experimentally the synchrony of host and endophyte seasonal abundance for any host–endophyte system. A correlation study of time series data on abundance indicated that in 1997 and 1998 seasonal synchrony occurred for both host–endophyte associations; this was predicted for interactions where the host is highly seasonal and the host–endophyte relationship is highly specific. We suggest that Acrosiphonia's sporophyte phase may have evolved to synchronize colonization with increasing host abundance, and synchronize reproductive phenology and host exit (as zoospores) with decreasing host abundance.

DEVELOPMENT, TAXONOMIC SIGNIFICANCE AND ECOLOGICAL ROLE OF THE CUTICULAR EPITHELIUM IN THE SANTALALES

All genera in the mistletoe family Viscaceae develop a secondary protective covering, the cuticular epithelium, that replaces the epidermis. The cuticular epithelium also occurs in the Eremolepidaceae and some genera within the related family Santalaceae. This secondary covering, unlike the periderm, lacks lenticels or their functional equivalent. We suggest that the cuticular epithelium provides a greater degree of control over transpirational water loss in older plant parts. The cuticular epithelium may arise in the epidermis, subepidermal layer, or in deeper tissues of the stem. Bark strands of the endophytic system, where they are in contact with either nonliving host tissues or the external environment, also form a cuticular epithelium. The epidermal feature, stomatal orientation, was also studied. All genera in the Viscaceae and Eremolepidaceae have stomata with a transverse orientation. The presence or absence of a cuticular epithelium and stomatal orientation are vegetative characters with potential taxonomic value.

The current and potential contribution of asymbiotic nitrogen fixation to nitrogen requirements on farms: a review

Significant levels of biological nitrogen fixation from sources other than nodulated legumes have become a tantalizing prospect for decades. Since the benefit to agriculture of nitrogen fixation from nodulated legumes was established, there have been widespread efforts to promote the use of various asymbiotic diazotrophic bacteria to fix extra nitrogen in soil. Despite much optimism by scientists and farmers, this prospect remains to be realised. Recently, the prospect has been pursued with renewed enthusiasm and several commercialised products have appeared. What are the reasons for this fresh enthusiasm? Are the new products based on realistic assessments of their biological potential? Why has it taken so long to advance to a stage where there is still only limited evidence that verifies hope becoming reality? This review assesses the current contribution from asymbiotic nitrogen fixation and re-assesses the prospects for greater contributions from this source. Among the many aspects of this multi-faceted subject that will be considered are: (i) the range of free-living microbial strains currently contributing to signficant asymbiotic nitrogen fixation; (ii) the significance of nitrogen-fixing microbes naturally associated with plants; (iii) the significance of endophytic systems and their role in sugarcane and other Gramineae; (iv) the possibility of extending this range by introducing new strains or discovering new systems capable of contributing additional nitrogen fixation. The case will be made that conditions providing a sustainable contribution for more than a short time are usually missing in such systems so that spontaneous biological nitrogen fixation is usually transient. It will be argued further that if all the positive factors controlling spontaneity at the biothermodynamic level are exploited, significant biological nitrogen fixation may soon be achieved in some of these systems on farms.

Transfer cells and flange cells in sinkers of the mistletoePhoradendron macrophyllum (Viscaceae), and their novel combination

The unusual thick-walled cells in contact with host and parasite vessels, first noted by Calvin 1967 in sinkers (structures composed of tracheary elements and parenchyma that originate from parasite bark strands that grow centripetally to the host vascular cambium and become embedded by successive development of xylem) of the mistletoePhoradendron macrophyllum (Englem.) Cockerell, have been investigated by modern methods of microscopy. The wall is thickest in cells abutting large-diameter host vessels, less so against smaller host vessels and those abutting sinker vessels. Transmission electron microscopy reveals the wall to be complex, consisting of a basement primary wall, upon which two developments of secondary-wall material occur. These are represented by lignified thickenings, in the form of flanges, and a labyrinth of wall ingrowths characteristic of a transfer cell. The wall ingrowths occur mostly in the primary-wall regions between the flanges, but when in contact with a large host vessel the ingrowths also differentiate on top of the flanges. Cells with such a transfer cell labyrinth have not been previously reported in the endophytic system of a mistletoe. The cells are confined to the xylary portion of the primary haustorium and sinkers. InP. macrophyllum, however, the cells differ from ordinary transfer cells in that they have differentiated as part of a flange parenchyma cell. This arrangement represents a novel anatomical situation. The name flange-walled transfer cell is used for these cells. The xylem of primary haustorium and sinkers also contain numerous ordinary flange cells. In both flange-walled transfer cells and ordinary flange cells the flanges are lignified and form a reticulate pattern of thickenings, separated by rounded areas of primary pit fields. The extent of development of the flange wall can vary in different parts of a sinker. At the host interface, the existence of a flange-walled transfer cell in direct contact with a vessel reflects a site associated with high loading into the parasite. Similarly, a labyrinth against a sinker vessel indicates a site of unloading from surrounding sinker tissue into the vessel for subsequent longdistance transport within the parasite.

Novel inoculants for an environmentally-friendly crop production

Abstract The high input of agrochemicals into soils is a major agricultural technique for enhancement of plant crop production, but it is also an environmental hazard. Concern over health hazards related to agrochemicals, especially on radioactively polluted territories, as well as economic problems, have promoted fundamental research to search for new agrobiotechnologies. Nonsymbiotic plant growth-promoting Rhizobacteria (PGPR) are often used as inoculants; however, they are not as effective as endophytic bacteria. These bacteria have the advantage of living within the plant tissue, protecting the plant from superinfection by soil bacteria, and recolonizing the plant surface after some stress situations in the soil. Although the use of beneficial microorganisms is not a new idea, it is an idea that is not heavily utilized. Application of inoculants designed on the base of competitive endophytic bacteria may be a full or partial alternative to agrochemicals, and can diminish the level of penetration and accumulation of heavy metals and radionuclides inside plants. This study evaluates the input of the association of the bacteria, isolated from the plant interior, in the crop of corn ( Zea mays ) and develops inoculants on their base. Nitrogen-fixing Klebsiella oxytoca VN13 along with Xanthomonas maltophilia VN12 were found to be useful bacteria, the former capable of excreting auxins and antimicrobial substances, the latter promoting assimilation of soil phosphorous by the plants. As the association of the two bacteria has been chosen as an effective endophytic system for the inoculant development, the two are mixed to form an inoculant ‘Duet’ which is directly inoculated into seeds. Corn inoculated with this ‘Duet’ produced greater yields, and possessed a greater percentage of protein. In addition, experiments performed in Chernobyl, showed that the ‘Duet’ could protect the plant from radionuclides penetration. It is suggested that a novel inoculant, ‘Kleps’, be applied, as the formulation is simple, it is inexpensive, it can be produced on a large scale, and it can be stored for a long period of time in a relatively small volume. It is clear that simple formulations of novel inoculants can be designed on the base of the competitive endophytic bacteria for an environmentally friendly crop production on poor and polluted territories as an alternative to the use of agrochemicals.

Thiol composition of a xylem-tapping mistletoe and the xylem sap of its hosts

Considerable amounts of low M r thiols were found in leaves, flowers and stems of the European mistletoe Viscum album (L.). Leaf thiol contents were the highest so far reported for green tissue. Thiol composition was similar in all mistletoe organs analysed. Glutathione was the predominant low M r thiol of V. album independent of xylem sap thiol composition of the host. From the present findings it may be concluded that either cysteine removed from the xylem sap of the host is rapidly incorporated into glutathione in the endophytic system, or glutathione is selectively removed from the xylem sap of the host. The significance of de novo reduction of sulphate taken from the xylem sap of the host for the mistletoe's thiol composition and content remains to be elucidated.

Étude de quelques aspects du métabolisme carboné et azoté chez l'Arceuthobium oxycedri, gui nain du genévrier

In juniper dwarf mistletoe, Arceuthobium oxycedri (DC) M. Bieb., a hemiparasitic and epiphytic Angiosperm characterized by very reduced and slow development, the chlorophyll content of the shoots is relatively high for a parasitic plant. However, gas exchanges reveal a low net gain in carbon, and the real photosynthetic intensity is only about 1.5 to 2 times higher than the respiratory intensity in these organs. In the endophytic system, which is also chlorophyllous, a small amount of photosynthetic activity also occurs. By studying 14CO2 assimilation and carboxylase activities in both organs, it was possible to determine the ability of the parasite to satisfy part of its carbon requirements. Following the administration of 14CO2, radioactivity was mainly recovered in carbohydrates and to a lesser extent in organic acids and amino acids. This demonstrates that A. oxycedri has some autonomy for the fixation and distribution of carbon into various compounds. On the other hand, the parasite, since it is epiphytic, is completely dependent upon its host for nitrogen. The study of the activities of the key enzymes of nitrogen metabolism ([Formula: see text] and [Formula: see text] reductases, glutamine synthetase, glutamate dehydrogenase, glutamate-oxalacetate transaminase) shows that nitrogen supply from the host certainly occurs mainly in the form of reduced nitrogenous compounds (ammonia and (or) aminated organic compounds). The numerous labelled amino acids recovered after administration of 14CO2 show that A. oxycedri is able to redistribute the imported nitrogen in various ways. Key words: Arceuthobium oxycedri, parasitic Angiosperms, carbon nutrition, nitrogen nutrition.

Establishment of the Mistletoe Phoradendron macrophyllum: Phenology of Early Stages and Host Compatibility Studies

The timing and morphological characteristics of the early stages in the establishment of Phoradendron macrophyllum (Viscaceae) on Salix laevigata were observed and quantified using clonal host material in greenhouse conditions. Observed stages were seed germination; holdfast formation; renewed greening of mistletoe tissue; swelling of the underlying host branch; aerial shoot formation; and development of the endophytic system. Aerial shoot formation was influenced by local moisture availability, but other stages in establishment were independent of water or nutrient sprays. When seeds of P. macrophyllum were placed on cuttings of Eucalyptus (a host susceptible to certain loranthaceous mistletoes, but not susceptible to Phoradendron), seed germination and hypocotyl swelling took place, but no further stages in holdfast formation occurred. A corky layer, or wound periderm, formed locally beneath the mistletoe seeds. When viscin alone from Phoradendron seeds was placed on Eucalyptus stems, wound periderm formation was also triggered.

Trophic Relations of the Dwarf Mistletoe Arceuthobium oxycedri with its Host Juniperus oxycedrus

Summary A basipetal transfer of 14 C-labelled assimilates is demonstrated from the host needles towards the aerial shoots of the parasite that acts as sink here. However, the endophytic system (= haustorium) of the parasite accumulates almost no radioactivity. The transferred substances are essentially soluble carbohydrates and amino acids (mainly asparagine). In the experimental conditions, the amount of carbon obtained from the host by the parasite may be estimated to be approximatively equal to the amount that it can fix from atmospheric CO 2 . The comparative study of mineral elements by X-ray microanalysis shows that the endophytic tissues of the parasite are richer in S, P and chiefly K than the close neighbouring host tissues, and consequently that the [K]/[Ca] ratio is higher in the parasite. It thus seems that mineral elements as well as organic compounds can be withdrawn by the endophytic system from both xylem and phloem of the host.

New Methods for Control of Leafy Mistletoe (Phoradendron spp.) on Landscape Trees

Leafy mistletoes in the genus Phoradendron parasitize many trees common in amenity and natural landscapes in the United States from coast to coast, where winter temperatures are moderate (Fig. 1). These parasitic angiosperms reduce the vigor of host trees such as Fraxinus, Juglans, Quercus, Gleditsia, Alnus, and others (5), by tapping the host tree xylem for water and mineral nutrients. Branches infected with mistletoe may die (7) and if the whole tree is exposed to other stresses, such as drought, the mistletoe may contribute to its death (8). Current recommendations for control of this pest include not planting susceptible species; removing mistletoe-infected branches at least 12 inches below the site of infection; or pruning the mistletoe cluster flush to the host branch and wrapping the infected area with black plastic, tar paper or aluminum foil (1). Mistletoe can also be pruned to a stub and treated with a formulation of (2, 4-dichlorophenoxy) acetic acid (2, 4-D) applied in a foam (1, 2, 8). While these control methods are effective, they are time consuming, expensive and potentially damaging to plants and humans. The City of Sacramento spent $1.4 million for mistletoe control in 1978-79, including some remedial treatment (5), and now Sacramento spends approximately $350,000 annually. Ethephon ([2-chloroethyl] phosphonic acid) is readily absorbed by plant tissues and then releases ethylene, a plant growth regulator affecting many physiological plant processes (6). When sprayed on intact clusters of leafy mistletoe, ethephon at 2% a.i. can cause complete abscission of the aerial parts of the parasite (3). Stress on the host is thus reduced, and mistletoe seed production is eliminated or delayed. We have observed, however, that regrowth of the mistletoe from buds or from the endophytic system can occur in the same season following such a treatment. In the present study, therefore, we tested for control of mistletoe regrowth by applying ethephon to cut stubs of Phoradendron, rather than to the whole aerial cluster. In our experiments, we tested the effects of ethephon on two species of Phoradendron parasitizing three host tree species. In the same experiments, we compared ethephon treatment to other materials, including the currentlyrecommended control, black plastic wrap. Black plastic works because it blocks light from penetrating to the host branch, so that the mistletoe cannot carry out the photosynthesis necessary to survive. We tested an aerosol pruning paint because it blocked out 97% of incident light, and might have an effect similar to black plastic. In addition, we tested glyphosate (N-[phosphonomethyl] glycine). Mistletoes reportedly do not translocate substances back to the host branches through the phloem (4), so we decided to test whether this systemic herbicide could kill the parasite without harming the host.

Growth of Longitudinal Strands of Phoradendron juniperinum (Viscaceae) in Shoots of Juniperus occidentalism*

To quantify the development of the mistletoe Phoradendron juniperinum within the branches of its host, Juniperus occidentalis, the growth of longitudinal (cortical) strands was measured. To begin, infections were classified positionally as either lateral (attached along sides of branches) or pseudoterminal (secondarily occurring at ends of branches). For both infection types five shoot dry weight classes were established, allowing comparisons, of growth of longitudinal strands to shoot dry weight. For lateral infections of all weight classes longitudinal strands showed greater basipetal than acropetal growth. In early stages of seedling establishement endophytic system spread is emphasized over shoot growth while in older plants shoot growth is emphasized; this feature is reflected in the dramatic decrease in spread/weight values over time. Comparisons between lateral and pseudoterminal infections of all weight classes revealed that lateral infections extend greater distances within host bark. Absorptive efficiency values were calculated. The determination of spread/weight and absorptive efficiency values represents a novel approach to endophytic system study that has applicability in physiological and ecological studies as well as in mistletoe-control methods

Le système endophytique d'Arceuthobium oxycedri. II. Aspects ultrastructuraux des zones de contact entre les tissus de l'hôte et du parasite

Ultrastructural study of the contact areas between the endophytic system of Arceuthobium oxycedri and the tissues of its host, Juniperus oxycedrus, shows that a crushed zone often occurs around the large cortical strands and along the primary sinkers in the secondary phloem of the host; such a structure seems rather unfavourable to the transfer of substances. On the other hand, the presence in the secondary xylem of half-bordered pits in direct contact with the cells of the primary and especially secondary sinkers certainly makes it easier for exchanges to take place. At the tip of the sinkers, the cells of the parasite, in the course of their growth, damage the cells of the host and sometimes penetrate into the lumen of its tracheids. Electron microscopy shows important acid phosphatase and ATPase activities at the level of the plasmalemma, plasmodesmata, and also some small endo- or exo-cytotic vesicles in the primary and secondary sinkers. Such activities are a sign of intense active transfer processes in these parts of the endophytic system. Around the contact zones, the parenchymatous cells of the host become very similar in aspect to those of the parasite.

Le système endophytique d'Arceuthobium oxycedri. I. Organisation, étude cytologique et cytochimique

In the endophytic system or haustorial apparatus that Arceuthobium oxycedri develops inside the parasitized branch of Juniperus, the present work shows that the cortical strands which connect the haustoria are either longitudinal or circular, that they always occur in the host secondary phloem, and that the smallest ones do not contain tracheids. Contrary to the secondary haustoria, in which parenchyma cells and tracheids are irregularly distributed, the primary haustoria have a more elaborate structure. At the ultrastructural level, the endophytic system is characterized by the presence of chloroplasts in all parts, including the tip of the haustoria, where these are, however, less differentiated. These plastids contain starch, but the cells are mainly rich in lipidic inclusions, especially in the deeper parts of the haustoria. Cell walls are always thick and endoplasmic reticulum profiles are locally abundant. In comparison with the corresponding healthy tissues, the host tissues neighbouring the endophytic system also become richer in starch and lipid inclusions.

Anatomy and ultrastructure of the endophytic system of Pilostyles thurberi (Rafflesiaceae)

The endophytic system of Pilostyles thurberi Gray consists of initially uniseriate filaments which develop into an anastomosing complex of larger cortical strands and radial sinkers. In the cortical strands three cell types are recognized, two of which differ largely in the density of the cytoplasm, the shape of the nucleus, and the degree to which the cytoplasm becomes plasmolyzed during fixation. The nuclei of both cell types contain two nucleoli which are physically connected by a nucleolar bridge. The third cell type demonstrates sieve plates, including a calloselike substance in the sieve pores and is consequently considered to be a sieve element. The sieve elements appear to form a discontinuous system and are regarded as a vestigial cell type. Plasmodesmal connections across the host–parasite interface have not been observed.

The ultrastructure of dwarf mistletoe (Arceuthobium spp.) sinker cells in the region of the host secondary vasculature

Sinker cells showed ultrastructural similarities in three species of Arceuthobium on three different hosts despite differences in season of collection and fixation. All species had abundant osmiophilic lipid bodies, plastids with prolamellarlike bodies, mitochondria with large nucleoids, chromocentric nuclei, and peculiar saccules associated with plasmodesmatal fields. Xylem may not be continuous through sinkers. Apoplastic continuity between host and parasite is afforded by fused cellulosic cell walls. Pitlike wall thinnings and "half-plasmodesmata" are found between juxtaposed host and parasite cells. One-sided, imperforate sieve pores were noted between a sieve cell and a contiguous sinker cell. However, symplastic isolation of the host and parasite seems likely. Therefore, nutrients may be absorbed from the common host–parasite apoplast. Mobilization of nutrients out of the endophytic system to the aerial shoots is thought to be facilitated by differential starch storage in the parasite body.

DEVELOPMENT OF JANCZEWSKIA MORIMOTOI (CERAMIALES) ON ITS HOST LAURENCIA NIPPONICA (CERAMIALES, RHODOPHYCEAE)1

ABSTRACT Janczewskia morimotoi Tokida was successfully cultured from spore to reproductive maturity on its host Laurencia nipponica Yamada. The spore penetrates the host without requirement for wound or abrasion sites, growing between host cortical cells and developing a superficial and an endophytic system simultaneously. During the juvenile period, when the parasite is nonpigmented, it differentiates a cortex and the proliferating endophytic filaments enlarge causing a displacement of layers of host cells into the parasitic tissue. Host cells contacted by cells of the parasite exhibit increased wall thickness, cytoplasmic density and vesicle formation. Pit connections between host and parasite cells were rarely observed whereas penetration of host cell walls was seen commonly. As the parasite increases in size, its cells become pigmented evenly throughout the cortex and host cells show less obvious reactions to the parasite. At this same time, the parasite develops branches and reproductive structures. Host plant segments less than 3 cm long failed to grow when infected with spores of the parasite whereas longer segments were not significantly affected by the parasite. In the absence of the host, the parasite cannot complete its development. Although J. morimotoi is well pigmented at maturity, the absence of pigmentation in the juvenile stage, penetration of host cells, and effect on host growth in culture strongly suggest that it is parasitic during at least its early development.

The ultrastructure of Arceuthobium pusillum

The endophytic system (ES) of Arceuthobium pusillum in Picea mariana, a compatible host, ramified throughout branchlets composing witches' brooms, and its cells contained numerous nonmembranebound droplets composed largely of neutral fats which occupied much of the cytoplasmic volumes and which persisted in senescent cells. The ES in the less compatible Larix laricina was found to persist mostly in tissues adjacent to and in spur shoots, and, in less vigorous infections, it accumulated fewer lipid droplets. In more successful infections of larch, many droplets were observed. Although the droplets probably serve for storage of high-energy fats, their accumulation in L. laricina appears to be reflected in the degree of success which the parasite has in this host. The more successful the infection, the more abundant are lipid droplets. Rapid lipid synthesis by the parasite may help to maintain a sharp carbohydrate diffusion gradient from host to parasite. The lipid droplets in both hosts were often in physical contact with smaller, single membrane-bound, evenly staining bodies which may have been involved in synthesis or use of these lipids. Germinating seeds, aerial shoots, and ES of the parasite in both hosts contained functional chloroplasts that structurally resemble those in the Gramineae that use the C4-dicarboxylic acid pathway.