Leaf Undersurface Research Articles

CORRELATES OF LEAF OPTICAL PROPERTIES IN TROPICAL FOREST SUN AND EXTREME‐SHADE PLANTS

Thirteen shade‐adapted rain forest species were compared with twelve sun‐adapted tropical forest species for correlates to leaf optical properties (described previously in Amer. J. Bot. 73: 1100–1108). The two samples were similar in absorptance of quanta for photosynthesis, but the shade‐adapted taxa: 1) had significantly lower specific leaf weights, indicating a more metabolically efficient production of surface for quantum capture; 2) synthesized less chlorophyll per unit area; and 3) used less chlorophyll for capturing the same quanta for photosynthesis. The anatomical features that best correlate with this increased efficiency are palisade cell shape and chloroplast distribution. Palisade cells with more equal dimensions have more chloroplasts on their abaxial surfaces. This dense layer of chloroplasts maximizes the light capture efficiency limited by sieve effects. The more columnar palisade cells of sun‐adapted taxa allow light to pass through the central vacuoles and spaces between cells, making chloroplasts less efficient in energy capture, but allowing light to reach chloroplasts in the spongy mesophyll. Pioneer species may be an exception to these two groups of species. Three pioneer taxa included in this study have columnar palisade cells that are extremely narrow and packed closely together. This layer allows little penetration of light, but exposure of the leaf undersurface may provide illumination of spongy mesophyll chloroplasts in these plants.

Peronospora violae . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Peronospora violae . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Viola acutifolia, V. arvensis, V. biflora, V. calarata, V. canina, V. cornuta, V. kitaibeliana, V. palustris, V. reichenbachiana, V. riviniana, V. silvestris, V. tricolor, V. tricolor var. arvensis, V. wittrockiana . DISEASE: Downy mildew of Viola spp. (violet and pansy); the fungus is an obligately biotrophic plant pathogen. In the early stages of the disease, a light covering of sporophores may be seen on the undersurface of individual leaves, unaccompanied by a colour change in the leaf. Later yellow patches appear on the upper surface of leaves covering a part of, or the whole lobe corresponding with patches of grey down on the leaf undersurface. Infected leaves eventually turn brown and die. Not all shoots are infected. Mildew first appears in October and progresses rapidly in November if the climate is mild and damp, or more slowly if dry. GEOGRAPHICAL DISTRIBUTION: Asia: USSR (Khazakhstan). Europe: Austria, Belgium, Czechoslovakia, Denmark, Finland, France, Germany (GDR, GFR), Hungary, Italy, Norway, Poland, Rumania, Sweden, Switzerland, United Kingdom, USSR (Estonia, Latvia, Russia, Ukraine, White Russia), Yugoslavia. See CMI Distribution Maps of Plant Diseases 599. TRANSMISSION: Boudier (1987) states that 'spectacular attacks of mildew follow sprinkler watering in dry autumn weather', suggesting that dispersal of spores may occur by a water splash mechanism. No other reports have been published.

Food availability for forest birds: effects of prey distribution and abundance on bird foraging

To evaluate availability of food for passerine birds in a northern hardwood forest, we measured the abundance and distribution of Lepidoptera larvae, a major food type, on the foliage of the dominant tree species and the foraging behaviour used by birds to capture prey from foliage substrates. Larval abundances averaged 2.1 per 400-leaf sample, and differed significantly among tree species and strata and within and between years. Although American beech had significantly higher larval densities, yellow birch hosted a greater proportion of free-living larvae, which were more readily available to foraging birds. Most larvae (78–91%) were found on leaf blades, with 62–75% on leaf undersurfaces. Bird species differed significantly in the frequencies at which they attacked prey on different foliage substrates (upper or lower leaf surfaces, petioles, twigs) and tree species. Several changed their foraging patterns from one tree species to another. Six of the 10 bird species directed attacks to substrates in proportion to the abundance of larvae there; the other 4 deviated from this pattern because of preferences for other kinds of prey or because of different abilities to perceive and capture prey from trees with differing foliage structures. Our results suggest that availability of food for forest birds is a function of (i) the types and abundances of prey present, which vary among tree species, (ii) the foliage structure and characteristics of the trees, which influence prey detectability and accessibility, and (iii) the morphological and behavioural abilities of each bird species to perceive and capture those prey. Food availability therefore cannot be assessed by simply measuring prey abundance alone and must essentially be determined separately for each bird species. Since each tree species provides a differing set of foraging opportunities for birds, the mix of tree species at a site, coupled with the arthropod resources they support, will influence which bird species can successfully exploit that habitat and hence will affect bird community structure.

LEAF OPTICAL PROPERTIES OF RAINFOREST SUN AND EXTREME SHADE PLANTS

The optical properties of the leaves of twelve tropical sun species and thirteen tropical extreme shade species were examined with an integrating sphere attached to a spectroradiometer. Measurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350–1,100 nm. Although some shade species absorbed higher percentages of quantum flux densities for photosynthesis (400–700 nm, PPFD) than the mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total absorptance of energy 350–1,100 nm. Furthermore, the sun and shade species were identical in their shift of absorptance at wavelengths between 650 and 750 nm. The anthocyanic coloration of the leaf undersurfaces of two species polymorphic for this characteristic (Trionela hirsuta and Ischnosciphon pruinosus) is correlated with increased absorptance at the upper end of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.

Leaf Optical Properties of Rainforest Sun and Extreme Shade Plants

The optical properties of the leaves of twelve tropical sun species and thirteen tropical extreme shade species were examined with an integrating sphere attached to a spectroradiometer. Measurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350–1,100 nm. Although some shade species absorbed higher percentages of quantum flux densities for photosynthesis (400–700 nm, PPFD) than the mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total absorptance of energy 350–1,100 nm. Furthermore, the sun and shade species were identical in their shift of absorptance at wavelengths between 650 and 750 nm. The anthocyanic coloration of the leaf undersurfaces of two species polymorphic for this characteristic (Trionela hirsuta and Ischnosciphon pruinosus) is correlated with increased absorptance at the upper end of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.

Life-cycle variation inPanonychus akitanus Ehara (Acarina:Tetranychidae)

The life history ofPanonychus akitanus Ehara was studied in two Hokkaido populations on dwarf bamboos. The Sapporo population overwintered both as egg and female adult onSasa senanensis, and the Tomakomai population overwintered as egg onSasa apoiensis. Mites of the Sapporo population produced four or five generations from late April to late November or early December. The eggs that had overwintered began to hatch in mid-May, and this hatching period overlapped with that of eggs laid in late April by females that had overwintered. Therefore, mites with different overwintering stages would interbreed. Most eggs that had overwintered in the Tomakomai population hatched in mid-May, and about four generations were produced before early December, when only eggs were found. The density of mites per leaf of the Sapporo population reached a maximum in early May on old leaves and in late June on new leaves, and thereafter gradually decreased. The Tomakomai population initially decreased in density after hatching in the spring, but rapidly dispersed to new leaves, reached a peak in early September, and then gradually decreased. The maximal density was about 10 times higher and the distribution was less clumped (lower values of the aggregation index,m/m) than that of the Sapporo population. This was probably because the Sapporo mites could utilize only the underside of sporadically distributed leaves which were curled by spiders, whereas the Tomakomai mites inhabited any part of the leaf undersurface of the hairy host plant. Predators observed were phytoseiid mites and larvae of gall midges. The predatory effect on the Sapporo population was not clear. In the Tomakomai population, the number of gall midges correlated with the number of spider mites better than that of phytoseiid mites.

Nature and Distribution of European Corn Borer (Lepidoptera: Pyralidae) Larval Feeding Damage to Cotton in North Carolina

European corn borer (ECB), Ostrinia nubilalis (Hübner), larval feeding behavior and damage on cotton were investigated from 1981 through 1983 in North Carolina. After eclosion, ECB larvae fed on the leaf undersurface for ca. 1 day before boring into plant structures such as leaf axils, stems, and bolls. Recent ECB feeding injury was characterized by the presence of a sawdustlike frass. During feeding, ECB larvae moved within a plant and between adjacent cotton plants. At the end of the growing season (late August through early October), the major portion of ECB feeding injury was on the large bolls, located in the middle third of the cotton plant.

Acaricide Treatments for Carmine Spider Mite in Cotton, 1984

Abstract Cotton was planted 14 May on 40 in rows. The experiment was arranged in a randomized complete block design with 3 replications of 5 treatments. Plots were 3 rows by 40 ft with 5-ft alleys between blocks. Two rows in each plot were treated leaving the third row as a buffer between contiguous plots. Treatments were applied using a CO2 backpack sprayer adjusted to deliver 10 gal of solution/acre through 2 TX-8 hollow cone nozzles per row at 35 psi and 3 mph. Treatments were made 16 and 21 Jul. Mites were counted in the field, on 16 (pretreatment), 20 and 25 Jul by examining 1 sq inch of leaf undersurface on 25 leaves per plot for the presence of adult female mites. The fourth leaf from the top of a randomly chosen plant was selected and the number of adult female mites were counted and recorded with the aid of a 1 OX “linen tester” lens centered on the leaf nectary.

The food plant preferences of Phratora vitellinae (Coleoptera: Chrysomelidae) : A. Field observations.

In the Upper Rhine (Petite Camargue, Saint Louis, France) study site, Ph. vitellinae are found mainly on Salix nigricans on which they are bivoltine. Some beetles are occasionally observed on S. purpurea, especially in Spring, but never on S. alba, S. caprea and S. cinerea. In other European localities, S. nigricans or S. hegetschweileri at higher elevations are frequently recorded as host-plants. However, some populations are also found on S. purpurea, P. tremula and P. trichocarpa x deltoïdes, usually when neither S. nigricans nor S. hegetschweileri are present.All the Salicaceae on which Ph. vitellinae was observed in the field have leaves rich in phenylglycosides and with glabrous lower surfaces, at least in Spring. Ph. vitellinae was never recorded on those Salix species with leaf undersurfaces densely covered with trichomes.At the time of emergence of the beetles from hibernation, S. nigricans leaves are more developed than those of S. purpurea and S. cinerea. Moreover, those S. nigricans trees with the longer shoots in Spring support the largest number of beetles at their emergence. The preference of Ph. vitellinae for S. nigricans might be reinforced by these plenological differences.In the Petite Camargue, the same S. nigricans trees support the largest populations of beetles from one generation to the next and from year to year. This suggests that S. nigricans does not respond to defoliation with induced resistance to the beetles.All shoots on the branch seem to be equally suitable and attractive for oviposition. The older leaves at the base of the shoot and the younger ones at the top are less favored by ovipositing females. Survival of the egg batches and the groups of freshly emerged larvae is lower on the distal shoots of the branch and on the younger leaves. This might be due to a higher degree of exposure to predators.

Flavonoids of Helianthus series Angustifolii

Leaf and ray flower flavonoids were investigated for the seven species of Helianthus series Angustifolii. Flavone aglycones occur in small glandular trichomes located on leaf undersurfaces of H. angustifolius, H. floridanus and H. simulans. Other species lacked both glandular trichomes and flavone aglycones. Flavonol glycosides occur in low concentrations in leaves of all species but were not characterized. Anthochlors (chalkones) occur in leaves of H. heterophyllus and H. longifolius. Ray flower flavonoids include anthochlor and flavonol glycosides and occur in the basal region of the ligule producing a band of UV A around the head. Anthochlors are the predominant ray flower flavonoids in H. angustifolius, H. heterophyllus and H. longifolius, whereas they are absent and quercetin 7-glucoside is present in H. carnosus and H. floridanus. Cladistic analysis of flavonoid and morphological characters indicates that evolution in the series has been a radiation from ancestral types rather than a linear sequence of progressively more derived species.

Leaf surface specializations of birds and Arthropods in a Panamanian forest.

Most species of Panamanian lowland forest birds specialize on leaf undersurfaces when hunting foliage insects. The few species of leaf surface generalists and leaf upper surface specialists are omnivorous gleaners. We estimate that while over 90% of the avian understory insectivory is directed towards leaf undersurfaces, only 50% of canopy foliage insectivory is directed towards the undersides of leaves. In the low understory we found 70-80% of the arthropods on leaf undersides. The excess use of leaf-bottoms by understory birds may be a result of their greater visibility. It is hypothesized that less proficient insectivores are unable to take advantage of the greater effective density of underleaf insects because they can only efficiently attack the closest leaf surfaces; these closest surfaces will usually be the leaf tops from the branch on which the bird is perched. Alternatively, leaf-top specialists may have special foraging adaptations for overcoming the disadvantages of leaf-top foraging. These adaptations may involve attack behavior (Tachyphonus luctuosus) or searching behavior (Dacnis cayana). Dacnis often used leaf damage as a foraging cue; this may be the first report of a bird using leaf damage for searching for insects. The greater use of leaf upper surfaces by canopy birds may be influenced by four factors: greater seasonality of insects in the canopy favoring omnivores which may be less efficient insectivores; more insects on leaf tops; fewer planar leaf arrangements in canopy plants; or the greater visibility of leaf upper surfaces of the outer shell of foliage of massive trees. Based on the greater number of arthropods on leaf bottoms in the dry season, the higher abundance of smaller insects on leaf bottoms, as well as the greater proportion of insects on leaf tops at cooler higher elevations, we suggest that arthropods prefer leaf bottoms in tropical areas for physiological, not predator avoidance reasons.

Foliar nectar production and ant activity on a neotropical tree, Ochroma pyramidale.

In second growth forest in lowland Costa Rica, ants forage at the foliar nectaries of juvenile Ochroma pyramidale. The relationship between leaf development, foliar nectar production and ant visitation indicates that nectar secretion and ant maintenance are greatest following rapid leaf expansion. Nectar measurements in the glasshouse corroborate field measurements showing that nectar production on a sapling is continuous through time and correlated with distribution and abundance of ants within a sapling. The presence of two nectary types, leaf vein and petiolar, on the leaves of O. pyramidale results in the continual maintenance of ants on the leaf undersurface. Nectar production of a sapling increases with increasing leaf area resulting in greater number of ants per sapling. Energetic costs of nectar production and ant maintenance appear low, representing about one per cent of the total energy invested in leaves.Spatial and diurnal patterns of ant activity changed very little over the study period. Removal and exclusion of ants from saplings results in the utilization of foliar nectar by trigonid bees. A significant difference in leaf damage between ant-visited and unvisited saplings, coupled with ant behavioral characteristics, is consistent with the hypothesis that ants act as antiherbivore agents on Ochroma.

A new genus and species of mealybug with a consideration of morphological convergence in three arboreal species (Homoptera: Pseudococcidae)

Abstract Descriptions and illustrations are given of male and female instars of the mealybug Plotococcus eugeniae, gen.n. and sp.n. This pseudococcid inhabits the dense hammock vegetation of southern Florida and is found primarily on Eugenia. It has the unusual habit of infesting many microhabitats on leaf undersurfaces rather than limiting its distribution to primary and secondary veins as do most leaf‐inhabiting mealybugs. Plotococcus eugeniae has unusually long legs, tarsal claws, antennae, and lateral wax filaments. Leptococcus metroxyli Reyne from New Guinea and Macrocepicoccus loranthi Morrison from Guyana also have these features. These species are redescribed and illustrated, and morphological comparisons are given that document the similarity of gross body structure among all three taxa. Evidence is presented suggesting that the unique morphology of these species has evolved independently through selection for dispersal as adult females.

A DEVELOPMENTAL STUDY OF THE LEAVES OF NICOTIANA GLUTINOSA AS RELATED TO THEIR SMOG–SENSITIVITY

Glater, Ruth Bobrov, Richard A. Solberg, and Flora M. Scott. (U. California, Los Angeles, and Los Angeles County Air Pollution Control District.) A developmental study of the leaves of Nicotiana glutinosa as related to their smog‐sensitivity. Amer. Jour. Bot. 49(9): 954–970. Illus. 1962.—Plants growing in the fields of Los Angeles County as well as those experimentally fumigated in the laboratory show gross markings in response to smog which vary from species to species, from a glistening appearance of the leaf undersurface due to a temporary accumulation of water in the affected cells through complete necrosis. In dicotyledonous leaves, “silvering,” “bronzing,” brown‐black mottling or an increase in anthocyanin may be seen. In monocotyledons, transverse banding, tan in color, or longitudinal streaking of leaves are the usual responses. This damage appears in a characteristic pattern on the leaves, different from that produced by other phytotoxicants. Nicotiana glutinosa plants were grown in the air‐filtered greenhouses at UCLA. The normal anatomical development of the foliage was studied and correlated with its susceptibility to smog injury. On a given plant, leaves of different ages show damage in different positions. Very young leaves at the apex of the plant and old leaves at the base of the plant are not sensitive. Expanding leaves between young and old in age are sensitive; in this group a distinct pattern of damage is discernible. Damage markings in the youngest leaves appear only at the tip; in leaves somewhat older, close to midblade; in fully mature leaves, only at the base. This localization of damage is shown to be correlated with the gradient of cellular differentiation from tip toward base as the leaf matures. Those cells which have just attained maximum size (young mature) are sensitive; damage, therefore, is a function of cellular development and maturity. The following anatomical details were analyzed: (1) differentiation and distribution of stomata and their opening and closing on both upper and lower epidermal surfaces and (2) development of intercellular air spaces in palisade and spongy parenchyma tissue. These studies indicate that damage occurs in the region of the leaf where stomata have just become functional and ambient polluted air can make direct contact with interior leaf tissues by virtue of large substomatal chambers and intercellular air spaces.

A Developmental Study of the Leaves of Nicotiana glutinosa as Related to Their Smog-Sensitivity

Glater, Ruth Bobrov, Richard A. Solberg, and Flora M. Scott. (U. California, Los Angeles, and Los Angeles County Air Pollution Control District.) A developmental study of the leaves of Nicotiana glutinosa as related to their smog-sensitivity. Amer. Jour. Bot. 49(9): 954–970. Illus. 1962.—Plants growing in the fields of Los Angeles County as well as those experimentally fumigated in the laboratory show gross markings in response to smog which vary from species to species, from a glistening appearance of the leaf undersurface due to a temporary accumulation of water in the affected cells through complete necrosis. In dicotyledonous leaves, “silvering,” “bronzing,” brown-black mottling or an increase in anthocyanin may be seen. In monocotyledons, transverse banding, tan in color, or longitudinal streaking of leaves are the usual responses. This damage appears in a characteristic pattern on the leaves, different from that produced by other phytotoxicants. Nicotiana glutinosa plants were grown in the air-filtered greenhouses at UCLA. The normal anatomical development of the foliage was studied and correlated with its susceptibility to smog injury. On a given plant, leaves of different ages show damage in different positions. Very young leaves at the apex of the plant and old leaves at the base of the plant are not sensitive. Expanding leaves between young and old in age are sensitive; in this group a distinct pattern of damage is discernible. Damage markings in the youngest leaves appear only at the tip; in leaves somewhat older, close to midblade; in fully mature leaves, only at the base. This localization of damage is shown to be correlated with the gradient of cellular differentiation from tip toward base as the leaf matures. Those cells which have just attained maximum size (young mature) are sensitive; damage, therefore, is a function of cellular development and maturity. The following anatomical details were analyzed: (1) differentiation and distribution of stomata and their opening and closing on both upper and lower epidermal surfaces and (2) development of intercellular air spaces in palisade and spongy parenchyma tissue. These studies indicate that damage occurs in the region of the leaf where stomata have just become functional and ambient polluted air can make direct contact with interior leaf tissues by virtue of large substomatal chambers and intercellular air spaces.