Skip to main content Accessibility help

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

  • Chester G. McWhorter (a1), Rex N. Paul (a2) and J. Clark Ouzts (a3)


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.



Hide All
1. Amarasinghe, V. 1990. Polysaccharides and protein secretion by plant microhairs. A cytochemical study at light and electron microscopic levels. Protoplasma 156:4556.
2. Amarasinghe, V. and Watson, L. 1988. Comparative ultrastructure of microhairs in grasses. Bot. J. Linnean Soc. 98:303319.
3. Amarasinghe, V. and Watson, L. 1989. Variation in salt secretory activities of microhairs in grasses. Aust. J. Plant Physiol. 16:219229.
4. Boize, L., Gudin, C., and Purdue, C. 1976. The influence of leaf surface roughness on the spreading of oil spray drops. Ann. Appl. Biol. 84:205211.
5. Cain, A. J. 1947. The use of Nile blue in the examination of lipoids. Q. J. Microsc. Sci. 88:383392.
6. Cawood, A. H., Potter, V., and Dickinson, H. C. 1978. An evaluation of Coomassie brilliant blue as a stain for quantitative microdensitometry of protein in sections. J. Histochem. Cytochem. 26:64650.
7. Chayen, J., Bitensky, L., and Butcher, R. G. 1973. Practical Histochemistry. New York, Wiley. 171 pp.
8. Cutter, E. G. 1978. Plant Anatomy. Addison-Wesley Pub. Co., London. 315 pp.
9. Egley, G. H., Paul, R. N, and Lax, A. R. 1986. Seed coat imposed dormancy. Histochemistry of the region controlling onset of water entry into Sida spinosa seeds. Physiol. Plant. 67:320327.
10. Ellis, R. P. 1979. A procedure for standardizing comparative leaf anatomy in the Poaceae. II. The epidermis as seen in surface view. Bothalia 12:641671.
11. Esau, K. 1953. Phloem. Page 275303 in Plant Anatomy. John Wiley and Sons, Inc., New York.
12. Fahn, A. 1974. Plant Anatomy, 2nd ed. Pergamon Press, Oxford, U.K. 294 pp.
13. Fahn, A. 1988. Secretory tissues in vascular plants. New Phytol. 108:229257.
14. Hardman, R. and Sofowora, E. A. 1972. Antimony trichloride as a test reagent for steroids, especially diosgenin and yamogenin, in plant tissue. Stain Tech. 47:205208.
15. Holloway, P. J. 1970. Surface factors affecting the wetting of leaves. Pestic. Sci. 1:156163.
16. Jensen, W. A. 1962. Botanical Histochemistry: Principles and Practice. W. H. Freeman and Co., San Francisco. 408 pp.
17. Johnston, C. R. and Watson, L. 1976. Microhairs: a universal characteristic of nonfestucoid grass genera? Phytomorphology 26:297301.
18. Levering, C. A. and Thompson, W. W. 1971. The ultrastructure of the salt gland of Spartina foliosa . Planta 97:183196.
19. Levering, C. A. and Thompson, W. W. 1972. Studies on the ultrastructure and mechanism of secretion of the salt gland of the grass Spartina . Proc. Elec. Micro. Soc. Am. 30:222223.
20. Mazia, D., Brewer, P. A., and Alfert, M. 1953. The cytochemical staining and measurement of protein with mercuric bromphenol blue. Biol. Bull. 104:5767.
21. Metcalfe, C. R. 1960. Anatomy of monocotyledons, Vol. I. Gramineae. Clarendon Press, Oxford. 731 pp.
22. McManus, J. F. A. 1948. Histological and histochemical use of periodic acid. Stain Technol. 23:99108.
23. McWhorter, C. G. 1971. Anatomy of johnsongrass. Weed Sci. 19:385393.
24. McWhorter, C. G. and Paul, R. N. 1989. The involvement of cork-silica cell pairs in the production of wax filament in johnsongrass (Sorghum halepense). Weed Sci. 37:458470.
25. McWhorter, C. G., Ouzts, C., and Paul, R. N. 1993. Micromorphology of johnsongrass (Sorghum halepense) leaves. Weed Sci. 41:583–58.
26. Mowry, R. W. 1956. Alcian blue technics for the histochemical study of acidic carbohydrates. J. Histochem. 4:407.
27. Mowry, R. W. 1960. Revised method producing improved coloration of acidic polysaccharides with Alcian Blue 8GX supplied currently. J. Histochem. Cytochem. 8:323.
28. Oross, J. W. and Thompson, W. W. 1982. The ultrastructure of salt glands of Cynodon and Distichlis (Poaceae). Am. J. Bot. 69:939949.
29. Paul, R. N., McWhorter, C. G., and Ouzts, J. C. 1990. An investigation into the ultrastructural histochemistry of glandular trichomes of johnsongrass [Sorghum halepense (L.) Pers.] leaves. Proc. Elect. Micro. Soc. Am. 50:842843.
30. Reeve, R. M. 1951. Histochemical tests for polyphenols in plant tissue. Stain Technol. 26:9196.
31. Sterling, T. M., Houtz, R. L., and Putnam, A. R. 1987. Phytotoxic exudates from velvetleaf (Abutilon theophrasti) glandular trichomes. Am. J. Bot. 74:543550.
32. Tateoka, T., Inoue, S., and Kawano, S. 1959. Notes on some grasses IX: systematic significance of bicellular microhairs of leaf epidermis. Bot. Gaz. 121:8091.
33. Wagner, G. J. 1991. Secreting glandular trichomes: more than just hairs. Plant Physiol. 96:675679.
34. Werker, E. and Fahn, A. 1981. Secretory hairs of Inula viscosa (L.) AIT—Development, ultrastructure, and secretion. Bot. Gaz. 142:461476.


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

  • Chester G. McWhorter (a1), Rex N. Paul (a2) and J. Clark Ouzts (a3)


Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed