Named for the Leonard Fuchs, a sixteenth century botanist and physician, fuchsias (Figures 1 and 2) belong to the order Onagraceae, which includes other herbs and shrubs such as evening primroses and clarkias. Natives to tropical and subtropical regions of Central and South America and to New Zealand and Tahiti, fuchsias have found their way to many cosmopolitan regions around the world. Their beauty, diversity and hardiness make fuchsias popular indoor and garden plants. Indoors and in greenhouses, fuchsias can be cultivated as pot plants or in hanging baskets. They are valued for their ornate, pendulous flowers, which range in shape from tubular to bell and in color, from red and purple to white. The exquisite shape and beauty of the fuchsia flower earned it the popular name "Lady’s Eardrop".

Fuschias are susceptible to whitefly infestation, a common and widespread condition ailing greenhouse and indoor plants. Whiteflies (Figure 3) are primarily tropical insects, but are commonly found in greenhouses, on houseplants and on some garden plants in the North during the summer (Wescott, 1964). They are minute, soft-bodied sucking insects that belong to the family Aleyrodidae of the order Hemiptera (suborder Homoptera). Whiteflies derive their name from the white, waxy abdominal secretion that is used to coat the bodies and wings of adult. They have two pairs of broadly rounded wings, making them appear like white moths. Whiteflies reside in great numbers on the underside of leaves, where they suck the sap of plants, causing wilting, and stunting or even death. The adult whiteflies secrete another substance called honeydew on which mold and fungi can grow. The mold coats the leaf and prevents sunlight from reaching the leaf surface, causing reduced rates of photosynthesis. Mobile adult flies are infamous in international agricultural and horticultural arenas to serve as vectors for the transmission of plant viruses. Whiteflies have been documented to be responsible for transmitting the leaf-curl virus (Borah, 1998), yellow mosaic virus, (Borah, 1995, Borah and Nath, 1995) and the tomato chlorisis virus (Wisler, 1998) among other viral diseases. Thus, whitefly infestation causes substantial damage to plants.

The diseased fuchsias used in this experiment were adopted from the Lyman Plant House at Smith College during the summer of 1999 as decorative indoor plants. Despite repeated spraying and rinsing with soapy water, whiteflies persisted to infest the leaves. Over the following six months, the fuchsias started to wilt and die. The goal of this experiment was to examine the effects of whitefly infestation on the upper and lower surfaces of the fuchsia leaves through scanning electron microscopy. The experiment allowed the concomitant comparison of the morphology of the upper and lower leaf surfaces, as well as the visualization of the detailed features of whitefly nymphs.

Healthy fuchsia (species) leaves were obtained with permission from the Lyman Plant House at Smith College. Diseased leaves were collected from a fuchsia (Hedicote beautu) plant adorning the Calculational Chemistry Laboratory at Smith College. The state of health of fuchsia plants was determined by inspection by the naked eye. Healthy plants had dense and perky green foliage; individual leaves were free of whiteflies and honeydew. Diseased plants were wilted; the underside of their leaves housed large numbers of whiteflies and was coated with little white spots. From each leaf was obtained several 5 mm discs, which were etched using a razor blade for identification purposes. Careful selection was exercised during sampling to ensure that all the specimen discs contained a vein, and if of diseased leaves, exhibited visible evidence of whitefly infestation. 

Dehydration of the specimen discs was performed based on a rapid fixation method developed by Neinhuis et.al. The discs were immersed in anhydrous methanol for one hour. During this period, the methanol was replaced at 20-minute intervals. The specimens were critical point dried in CO₂ at 5^oC, left overnight to warm to room temperature and mounted on stubs using carbon paint. Of the two specimen discs obtained from the same leaf, one was mounted with its top surface up and the other with its bottom surface up. This allowed both the upper and lower epidermal surfaces of each leaf to be examined separately. A total of eight specimen discs were prepared, three of the lower surface of diseased leaves, three of the upper surface of diseased leaves and one each of the upper and lower surfaces of a healthy leaf. The mounted leaf specimens were coated with gold and palladium and examined using a JEOL JSM 6400 scanning electron microscope operated at an accelerating voltage of 5 kV.

Both the upper and lower surfaces were free of whitefly nymphs. The surfaces appeared to be clean, with little debris scattered about. Seen in Figure 4, the upper epidermal cells appear round, turgid. Their arrangement is orderly and in a regular fashion that resembles the roughly hexagonal packing found in fullerene molecules. Numerous stomata, each surrounded by swollen and raised guard cells were observed on the lower surface (Figure 5) but not on the top. The cells of the lower epidermis appear to be of a more irregular shape, possessing lobes that intercalate. Trichomes, hair-like structures that serve a variety of functions such as protection and secretion, were observed to be dispersed randomly both surfaces. There were at least two different types of trichomes found on the fuchsia leaves: one with a smooth, linear shaft and a rounded tip (Figure 6a) and the other with a curved, scaly shaft and a narrow, tapered tip (Figure 7).

Lower surface: Even at low magnification (~ 70 ´), one could observe up to eight insects on the lower surface of each specimen disc. Upon higher magnification, some of the insects appeared to be generally ovoid and without visible legs or antennae (Figure R4). These specimens were generally 200 m m in length, and not distinctly segmented. The surface of the insect body was seen to be axially symmetrical and contoured. Larger, flatter insects (Figure 9) were also observed on the lower surfaces. The larger insects were approximately 500 m m in length and possessed a border around the edge of their bodies. On closer inspection, the border was seen to be composed of filaments seemingly coated with plates of wax. (Figure 10). Oval insect eggs were present in small numbers (1 – 4 eggs per leaf disc). The eggs had smooth surfaces and were about 200m m long (Figure 11). Figure 12 shows a third form of the whiteflies found on the lower leaf surface. With a length of 900 m m, this was by far the largest insect form found on the fuchsia leaves appeared to be the shell of the whitefly which remained on the leaf after molting. There is a T-shaped opening on the upper surface allowed a glimpse into the interior of the insect form, showing it to be an empty casing. Long filaments emanate from the upper surface of the insect and arranged somewhat symmetrically about the central axis. The insect also appeared to have peripheral short filaments. All three observed insect forms possessed a unique trapezoidal opening on the upper surface of their bodies (Figure 13). Settled in this opening were two highly specialized structures. One is spherical and spiky (distal in Figure 13), and the other is shaped somewhat like a lady’s money purse, with considerably less protrusive surface texture (proximal structure in Figure 13).