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Confocal Microscopy Image Gallery
Plant Tissue Autofluorescence
Autofluorescence in plant tissues is a common and useful phenomenon arising from a variety of endogenous biomolecules that absorb light in many regions of the near-ultraviolet and visible light spectrum. One of the primary contributors of plant autofluorescence is chlorophyll, but lignins, carotenes, and xanthophylls also produce a significant level of fluorescence emission when stimulated with the proper wavelengths. This digital image gallery examines natural autofluorescence in plant tissue thin sections using multiple excitation wavelengths with laser scanning confocal microscopy.
Beet Fleshy Root - The fleshy root of the beet plant, Beta vulgaris, is commonly consumed as a vegetable when raw, cooked, or pickled. No other vegetable contains as much sugar as the beet root, a fact reflected in the sweetness of its taste. The greens of the plant are also edible and some varieties, known as leaf beets or Swiss chard, are grown specifically for their leaves.
Buttercup Stem - Buttercups are primitive dicotyledonous plants, evidence suggesting that they date back around 20 million years ago to the Early Miocene Era. Accordingly, the buttercup’s flower structure is rather simple, with each of its components existing as distinct entities rather than being fused into complex organs. Most buttercup flowers have five petals, numerous stamens, and clusters of unconnected pistils.
Cactus Stem - The thick, fleshy stems of cacti rarely exhibit leaves and instead typically bear numerous prominent spines, which offer them protection from a wide range of animals. Most cacti thrive in the desert, where several adaptations enable them to acquire and retain as much water as possible from the environment. More than 1,500 species of cacti have been identified, and there is significant variation in their size and shape.
Carnation Leaf - The species name of the carnation is Dianthus caryophyllus, and the flower belongs to the family Caryophyllaceae, also known as the pink family. Pinks characteristically exhibit fringed, or “pinked,” petals and stems with nodular swelling. The leaves of most carnations are narrow and bluish-green in color. Their scent is spicy, and the plants have been used in the past to spice wine and other drinks.
Carrot Taproot - The carrot plant, Daucus carota, is native to Afghanistan and surrounding regions, but has been cultivated in the Mediterranean since antiquity and from there gradually spread across the globe. The part of the plant commonly eaten as a vegetable is the long, narrow taproot that extends into the ground directly beneath the stem. In the United States, the taproot is traditionally bright orange, but carrots also naturally grow in white, yellow, and even deep purple hues.
Castor Bean Seed - Seeds of the castor bean plant, Ricinus communis, are highly poisonous and can cause death even when consumed in small quantities. The primary toxin the seeds contain is ricin, a lectin that inhibits protein synthesis in animal cells and leads to cell death. Symptoms of castor bean seed ingestion or other ricin exposure may include abdominal pain, vomiting, diarrhea, and convulsions.
Cattail Leaf - The pale leaves of cattails are basal, long, and erect. Their ribbon-like form makes them well suited for weaving into items such as baskets, mats, and rope. In cross-section, numerous air channels can be seen in the leaves, which are very spongy and absorbent. Due to this quality, cattail leaves have at times been used to caulk boats and stop small leaks.
Cherry Flower Bud - The flowers produced by cherry trees are prized for their delicate beauty. The small pink or white blossoms usually emerge in early spring, but do not remain intact for long since even gentle breezes can cause them to shed their elegant petals. The brief blooming of cherry trees is marked by festivities in many parts of the world, including Washington, DC.
Clubmoss Leaf - Despite their common name, clubmosses are not technically mosses, but rather are evergreen herbs usually included in the group of plants known as fern allies. Like ferns, clubmosses are flowerless and seedless, and have true leaves, stems, and roots. The primitive plants were once among the most dominant flora on Earth, growing nearly 100 feet high and being particularly abundant during the Carboniferous Era, 360 million to 286 million years ago.
Clubmoss Mature Stem - The life cycle of the clubmoss consists of alternating generations of familiar spore-producing plants and inconspicuous underground gametophytes. Clubmoss sporophytes often exhibit creeping or prostate stems, sometimes located underground, but certain species possess erect stems. The stems are almost always heavily branched and thickly covered with small, green leaves.
Clubmoss Root - Clubmosses frequently form dense mats of foliage, which are provided nutrients and water by their fibrous root systems. The roots are very fine and shallow, but are so extensively branched that some species can be problematic when they occur in pastures because they absorb all of the moisture available in their area of growth so that the amount of water accessible for grasses and other plant life typically consumed by cattle is limited.
Coleus Stem - Most cultivated species of coleus are native to Southeast Asia, Malaysia, and Java. The plants are heat-tolerant, but traditional strains of coleus thrive best in shaded areas. A revival of interest in the plants in the late 1990s, however, was marked by the introduction of a number of sun-loving, magnificently colored varieties. The plants are now available in a tremendous array of hues and patterns and are suitable for a significantly wider range of environments than before.
Corn Prop Root - The corn plant, Zea mays, is a cereal grass native to the Americas that has been cultivated for thousands of years. The stem of the plant is very tall and is usually supported by numerous prop roots that can be seen extending out from the stem’s base. Similar to other monocots, the primary root system of the corn plant is poorly developed and inadequate to serve as a sufficient foundation for its growth.
Corn Rust - Corn rust is caused by two different fungi, Puccinia sorghi and Puccinia polysora, the former causing common rust and the latter causing outbreaks of southern corn rust. Both forms of rust are exemplified by the presence of brownish-red pustules on the stems and leaves of the corn plant, particularly in areas of new growth. The pustules contain numerous tiny spores that can infect new tissue or other plants when they burst open.
Cottonwood Pollen - A few weeks each summer, clumps of cottony-coated seeds are shed by several North American tree species belonging to the genus Populus that, as a result, are commonly known as cottonwoods. The trees are dioecious, and only females shed the familiar white fluff. The cotton can be a nuisance and may clog gutters, air conditioners, and other items, but it is the pollen produced by male cottonwoods that is most problematic for individuals that suffer from allergies.
Cup Fungus - Some of the most eye-catching fungi in the forest are cup fungi, a large, colorful group of fungi with fruiting bodies that are cup or saucer shaped. Despite their relatively similar forms, cup fungi are extremely diverse, consisting of members from a number of different families and genera in the class Ascomycetes. The cup-like component of a cup fungus is termed the apothecium.
Cycad Leaf - Cycads are ancient, woody plants with large, pinnately compound leaves that cause them to often be confused with palms or ferns, though they are not closely related to either. The cycads comprise the order of Cycadales and, along with ginkgoes and conifers, comprise one of the world’s major groups of gymnosperms, plants that bear naked seeds. Only 11 extant genera of cycads are recognized containing only a few hundred species, many of which are rare or endangered.
Cycas Sporangia - As cycads, members of the Cycas genus are dioecious, with male and female reproductive structures found on different plants. Modified leaves on male plants termed microsporophylls are the sites of pollen production. In other cycads, the microsporophylls are arranged into strobili, but the Cycas genus is unique from them in that their microsporophylls are organized into a few spiral-like configurations at the apex of the stem rather than into a cone.
Dandelion Fruit - On warm spring and summer afternoons, children often enjoy blowing the ripe, tufted fruits of dandelions into the breeze and watching them lazily drift away. Each tuft carries a single seed, which may be deposited at great distances away, much to the chagrin of gardeners throughout the temperate regions the common weeds inhabit. The tufts of the dandelion fruit, known as pappi, act similar to tiny parachutes that keep the seeds aloft on air currents.
Elderberry Lenticel - About 30 different bushes and small trees belonging to the genus Sambuca are known as elderberries, or simply elders. Nearly all elderberry varieties produce large clusters of small white or yellowish flowers in the late spring or early summer, followed by wide bunches of berries. The elderberry fruit varies in color from yellow to red to bluish-black and can be used to make wines, jellies, syrups, and other edibles.
Fleabane Flower Head - Approximately 200 species are classified as fleabanes, most of which are annuals or biennials, though a few are evergreens. The plants are well-branched and may feature flowers in a variety of colors when in bloom. Some fleabanes resemble other well-known flower types, such as the daisy or aster, and their common names often reflect this fact.
Ginkgo Embryo - The ginkgo tree is a dioecious gymnosperm that produces microstrobili and ovules on separate individuals in the spring after maturity is reached. The male reproductive structures are similar in shape to small catkins and the female structures are naked, possess a fleshy integument, and occur in pairs. They both can be found on short spur shoots located at the bases of leaves.
Ginkgo Stem - As the only living member of a primitive order of gymnosperms (Ginkgoales), the ginkgo tree is a stalwart survivalist. The tree is a native of China and is scientifically described as Ginkgo biloba. The shelled seeds of the ginkgo are edible and are considered to have health benefits by some, but more commonly today extracts from the leaves of the tree are included in various health supplements.
Grass Leaf - Commonly grass is thought of as the short, green ground cover of lawns, but a wide variety of monocotyledonous flowering plants comprising the family Poaceae are grasses. The leaves of grasses vary somewhat in size, shape, and texture, but generally are elongate or elliptical and exhibit parallel veins. Three basic components comprise each leaf of a grass, the sheath, blade, and ligule.
Hair-Cap Moss Leaves - Hair-cap mosses comprise the genus Polytrichum of the order Polytrichales. Both the genus and common name of these mosses make reference to the hairy calyptra characteristic of the sporophyte capsules (sporangia) before they reach maturity. The capsules are very conspicuous, extending several inches into the air on long, narrow stalks and appearing similar to grains of wheat.
Hemlock Leaf - Members of the Tsuga genus of coniferous trees are popularly known as hemlocks, their common moniker stemming from the scent of their crushed leaves, which is said to resemble that of the unrelated herbaceous plant Conium maculatum, generally called poison hemlock. Despite their namesake, however, hemlock trees are not poisonous. The evergreens, which are native to North America and parts of Asia, are quite popular as ornamentals and grow best in locales that are humid and cool.
Hollyhock Rust - The hollyhock is a tall flowering plant belonging to the genus Alcea that is a traditional favorite of English cottagers. The plant has been cultivated in England since the Middle Ages, but is native to China. Hollyhocks are available in annual, biennial, and perennial varieties with blooms in several different colors, including white, yellow, pink, lavender, red, and even black.
Laminaria Blade - Several species of Laminaria are harvested for a variety of uses, including human consumption, iodine extraction, crop fertilization, and medical applications. The kelps usually range from about three feet to nearly ten feet long and range in color from light to dark brown. They are most plentiful along the coasts of the Pacific Ocean and in the north Atlantic around the British Isles.
Lilac Leaf - Lilacs are popular in American gardens due to their highly aromatic and beautiful flowers, but are not native to the area. The flowering shrubs and small trees were brought to the continent by European settlers and were featured in the gardens of some of the founding fathers of the United States, including George Washington and Thomas Jefferson.
Lily Flower Bud - Lilies have a long history of cultivation by humans, and were prized as ornamentals and as medicinal plants by several ancient civilizations. Much of the rich symbolic significance ascribed to certain colors and varieties of lilies today has its roots in the practices and beliefs of these early cultures. For example, white lilies are commonly carried in the bouquets of modern brides, a tradition related to the ancient Roman association between lilies and purity.
Maple Pollen - The appearance of maples varies considerably, but most exhibit thick, brightly colored foliage in the autumn months. Maples are among the most troublesome trees for allergy sufferers. The pollen they produce is highly allergenic and some species, especially the box elder, produce copious amounts of the microspores. In the United States, maple pollen season extends from February to May.
Orchid Root - The roots of many orchids have a symbiotic relationship with specialized fungi, and the tiny seeds of the plants require interaction with fungi to germinate naturally. More than 15,000 orchid species are recognized, most of which inhabit tropical regions, though some can be found in nearly all nonpolar locales. In several areas, rare orchids have been collected to such a great extent that protections have been put in place to save them from extinction.
Pear Fruit Sclereids - The pear fruit is commonly eaten fresh or canned, and in several countries is very popular for the production of perry, a drink made by fermenting pear juice. The texture of the pear is characteristically gritty, a quality that is related to the presence of special cells called sclereids or stone cells. Sclereids are variously shaped sclerenchyma cells with thick, lignified walls.
Pine Wood - All pines are technically softwood trees, but for commercial purposes members of the genus are regularly divided into hard pines and soft pines. The wood of hard pines is typically tougher, more coarse-grained, and darker in color than that of soft pines. Both kinds of pine are very valuable natural resources, with various species being utilized heavily in the paper manufacturing and construction industries.
Porphyra Algae - Porphyra algae may be prepared in a variety of ways before they are eaten. One of the most common practices is to shred the blades and press them into sheets to dry. In this form, Porphyra is often known as nori, a food item that can be used to make sushi, soups, fried snacks, and other dishes. Nori contains a variety of nutrients in significant amounts and is high in protein.
Potato Tuber - Potato plants form tubers as a site to store starch for gradual use during the winter months when photosynthesis often cannot be carried out. Each plant generally develops several of the special food reserves, some retaining twenty tubers or more at a single time. The tubers vary somewhat in size, shape, color, and texture, and there are more than 500 different varieties currently cultivated.
Privet Leaf - Privets are a group of bushes and small trees that comprise the genus Ligustrum. These members of the olive family, Oleaceae, grow rapidly and are generally simple to cultivate, characteristics that render several species of the plant popular as hedges. Privets are also desirable for their pleasant appearance, which is highlighted by dark green leaves and numerous panicles of fragrant white flowers.
Red Algae - Several thousand species of red algae have been identified and are classified together in the division Rhodophyta. Most are multicellular marine varieties that predominantly inhabit tropical and subtropical areas, though some are unicellular and prefer different habitats. The color of red algae, which is sometimes blue rather than red, is due to the presence of phycobilin pigments.
Red Seaweed - Seaweeds occur in several different colors, including red, brown, and green, and a wide range of sizes, from only a few inches to more than one hundred feet long. Despite their disparaging name, which is suggestive that the algae are undesirable or troublesome, many seaweeds are highly useful to humans. Certain species are extremely nutritious sources of food, while others have been utilized in such diverse applications as upholstering, curing leather, and the production of cosmetics.
Rubber Tree Leaf - The vast majority of natural rubber utilized for commercial purposes is acquired from Hevea brasiliensis, commonly known as the rubber tree. The tree is indigenous only to tropical and some subtropical areas of South America, and natives in these regions had been obtaining and utilizing the milky white juice known as latex from them for many years before the arrival of the first European explorers.
Selaginella Stem - Selaginella is a large genus of plants commonly known as clubmosses or spike mosses that are widely distributed around the globe. Around 600 species of Selaginella have been identified, and these exhibit significant variation in their structure, appearance, and preferred habitat. Some of the vascular plants appear similar to ferns and proliferate predominantly in the tropics, whereas others display simple scale-like leaves and creep across the ground like mosses.
Selaginella Strobilus - When the sporangia of a Selaginella strobilus reach maturity, they split open and release the spores they contain into the air. The megaspores give rise to female gametophytes known as megagametophytes and the microspores develop into male microgametophytes. The microgametophytes produce sperm equipped with flagella that enable them to swim to the eggs generated by a megagametophyte through water in order to achieve fertilization.
Shepherd’s Purse Floral Tip - Members of the genus Capsella, which is classified in the mustard family, are popularly known as shepherd’s purse. The common name stems from the unusual triangular, flattened seedpods characteristic of the genus that are reminiscent of simple leather purses. The small white flowers of the shepherd’s purse grow on racemes that develop from one or more stems that arise from the center of a rosette of basal leaves.
Sunflower Leaf - When sunflowers are in bloom, most of the flower heads face the east as if they want to greet the rising sun each morning. Before they blossom, however, sunflower buds actually track the sun’s path across the sky, slowly turning from east to west on bright sunny days before eventually returning to their eastward direction at night or first light the following morning.
Sweet Flag Stem - A thick subterranean stem called a rhizome allows sweet flag to easily propagate vegetatively and to survive harsh environmental conditions. Sweet flag rhizomes have a spicy fragrance and have been utilized by humans throughout history. Ancient Egyptians considered sweet flag rhizomes aphrodisiacs and various Native American tribes utilized them for both medicinal and ceremonial purposes.
Wheat Grain - The outer and innermost portions of wheat grain (the bran and the germ, respectively) are usually separated from the endosperm that lies between them during milling. The endosperm, which is high in starch and composes the bulk of the grain, is then commonly utilized to produce white flour.
White Pine Blister Rust - White pine blister rust is one of the most serious diseases affecting American forests. Stands of white pines can be easily devastated by the disease, which is caused by the fungus Cronartium ribicola. The pathogen was introduced to the United States via trees imported from Europe in the late 1800s and to Canada a few years later.
Contributing Authors
Nathan S. Claxton, Shannon H. Neaves, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.