Micromorphology of Johnsongrass (Sorghum halepense) Leaves

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 583-589 ◽  
Author(s):  
Chester G. Mcwhorter ◽  
Clark Ouzts ◽  
Rex N. Paul
Keyword(s):  
Leaf Surface ◽  
Epicuticular Wax ◽  
Epidermal Cells ◽  
Sorghum Halepense ◽  
Single Type ◽  
Cork Cell ◽  
Silica Cell ◽  
Stomatal Complexes ◽  
Epicuticular Wax Crystals ◽  
Wax Crystals

Adaxial and abaxial epidermal surfaces of johnsongrass leaves were studied to determine which cells contribute to leaf microroughness. Cork-silica cell (CSC) pairs, three types of prickles, macrohairs, bicellular trichomes, stomata, and ordinary short and long epidermal cells were found and described. CSC pairs made up about 22% of all cells and probably contribute more to microroughness than any other single type because each cork cell produces 11 ± 3 wax filaments that are up to 100 μm long. Bicellular trichomes represented 4 to 5% of the total cells but decreased leaf roughness by secreting a type of mucilage that covers microscopic wax crystals. Stomatal complexes comprised 15 to 18% of all cells and contributed to leaf roughness because they are slightly recessed below the leaf surface. Long prickles occur primarily over veins and represent less than 1% of all cells. Small prickles were present primarily on adaxial surfaces and represent only 3% of all cells. Macrohairs were the largest appendages, 237 ± 104 μm, but they represent far less than 1% of all cells and occur primarily over veins. Ordinary short cells comprised 6 to 13% of all cells. Long cells were most common (41%) of all cells. Short and long cells contribute to leaf roughness because the surface is often convex. A typical johnsongrass leaf may contain more than 25 million appendages on each surface that increase the roughness already caused by epicuticular wax crystals.

scholarly journals Impact of cell shape in hierarchically structured plant surfaces on the attachment of male Colorado potato beetles (Leptinotarsa decemlineata)

2012 ◽  
Vol 3 ◽  
pp. 57-64 ◽  
Author(s):  
Bettina Prüm ◽  
Robin Seidel ◽  
Holger Florian Bohn ◽  
Thomas Speck
Keyword(s):  
Cell Shape ◽  
Traction Force ◽  
Epicuticular Wax ◽  
Epidermal Cells ◽  
Epicuticular Wax Crystals ◽  
Cell Shapes ◽  
The Impact ◽  
Plant Surfaces ◽  
Wax Crystals ◽  
Insect Attachment

Plant surfaces showing hierarchical structuring are frequently found in plant organs such as leaves, petals, fruits and stems. In our study we focus on the level of cell shape and on the level of superimposed microstructuring, leading to hierarchical surfaces if both levels are present. While it has been shown that epicuticular wax crystals and cuticular folds strongly reduce insect attachment, and that smooth papillate epidermal cells in petals improve the grip of pollinators, the impact of hierarchical surface structuring of plant surfaces possessing convex or papillate cells on insect attachment remains unclear. We performed traction experiments with male Colorado potato beetles on nine different plant surfaces with different structures. The selected plant surfaces showed epidermal cells with either tabular, convex or papillate cell shape, covered either with flat films of wax, epicuticular wax crystals or with cuticular folds. On surfaces possessing either superimposed wax crystals or cuticular folds we found traction forces to be almost one order of magnitude lower than on surfaces covered only with flat films of wax. Independent of superimposed microstructures we found that convex and papillate epidermal cell shapes slightly enhance the attachment ability of the beetles. Thus, in plant surfaces, cell shape and superimposed microstructuring yield contrary effects on the attachment of the Colorado potato beetle, with convex or papillate cells enhancing attachment and both wax crystals or cuticular folds reducing attachment. However, the overall magnitude of traction force mainly depends on the presence or absence of superimposed microstructuring.

Bicellular Trichomes of Johnsongrass (Sorghum halepense) Leaves: Morphology, Histochemistry, and Function

Weed Science ◽  
1995 ◽  
Vol 43 (2) ◽  
pp. 201-208 ◽  
Author(s):  
Chester G. McWhorter ◽  
Rex N. Paul ◽  
J. Clark Ouzts
Keyword(s):  
Leaf Surface ◽  
Unit Area ◽  
Grain Sorghum ◽  
Sorghum Halepense ◽  
Structural Factors ◽  
Soil Mixture ◽  
Low Concentrations ◽  
And Function ◽  
Wax Crystals ◽  
Surface Microroughness

Studies were conducted of one of the structural factors that influences microroughness on johnsongrass leaves. Bicellular trichomes, 47 ± 5 μm long, represented 4 to 5% of all epidermal cells. They secreted a mucilagenous material that covered 8 ± 4% of the leaf surface. Bicellular trichomes occurred in longitudinal rows, intermixed with intercostal cork-silica cells, between rows of stomata. Numbers of bicellular trichomes present per unit area were inversely related to numbers of intercostal cork-silica cells. The trichomes were the panicoid type that are reported not to secrete salts. Johnsongrass trichomes, however, could be induced to discharge salt in the mucilage-type secretions when plants were grown in a soil mixture that was high in lime. Not all secretory constituents were identified, but carbohydrates and callose were found in addition to possible low concentrations of protein. The apical or cap cell of the trichomes stained positively for lipid, protein, and polysaccharide and negatively for pectin, polyphenols, steroids, and alkaloids. The presence of trichomes increases leaf surface microroughness, but the secretion covers wax crystals, decreasing leaf microroughness and likely providing another barrier to herbicide entry through the cuticle. Bicellular trichomes on grain sorghum were similar to those on johnsongrass and also discharged secretions on the leaf surface.

RELATIONSHIP BETWEEN EPICUTICULAR WAX AND BLACKSPOT CAUSED BY ALTERNARIA BRASSICAE IN THREE LINES OF RAPESEED

1976 ◽  
Vol 56 (4) ◽  
pp. 781-785 ◽  
Author(s):  
J. P. TEWARI ◽  
W. P. SKOROPAD
Keyword(s):  
Partial Resistance ◽  
Leaf Surface ◽  
Epicuticular Wax ◽  
Water Repellent ◽  
Minimal Amount ◽  
Alternaria Brassicae ◽  
Brassica Napus L ◽  
Physical Role ◽  
Wax Crystals

The physical role of epicuticular wax in rapeseed in conferring resistance to Alternaria brassicae (Berk.) Sacc. has been investigated using the adaxial surface of the upper leaves of three lines of rapeseed. The lines of rapeseed were selected to offer a range of bloom and degrees of resistance to A. brassicae. Scanning electron microscopy revealed that epicuticular wax is organized in two layers. The distal layer is fluffy and consists of cylindrical wax crystals, while the proximal layer has plate-like wax crystals. The distal layer is thicker in the Iowa line (Brassica napus L.) than in the cv. Midas (B. napus), while the proximal layer is almost similar in the two cultivars. Torch (B. campestris L.) has only a minimal amount of wax. Wiping of the leaves with cotton wool removes the fluffy wax layer. The amount of wax per cm2 of the leaf surface is maximum in the Iowa line, followed by that in Midas and Torch. The contact angle of water droplets is significantly reduced and retention of conidia and development of blackspots caused by A. brassicae are significantly increased upon wiping of the leaves in Iowa line and Midas but not in Torch. It is concluded that the bloom in rapeseed confers partial resistance to A. brassicae by providing a water-repellent surface.

Sign in / Sign up

Export Citation Format

Share Document