Cell wall thickness and cell dimensions in plant parts of eight forage species

To appreciate more clearly some of the physical characteristics of forages which may be important in relation to digestibility and structural integrity, different parts of eight plant species were examined for the proportion of thick-walled, thin-walled and epidermal cells, the thickness of the cell walls and the diameter, length and volume of the cells. The eight species were: Trifolium repens L., Medicago sativa L., Desmodium intortum (Mill.) Urb., Lolium perenne L., Festuca arundinacea Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and Zea mays L. Early harvesting was compared with later harvesting in each of two years. The plants were grown in a heated glasshouse in spring-summer. The plant parts with the lowest proportion of thick-walled cells (3-6% of cross-sectional area) were the legume leaflets and those with the highest proportion (47-57%) were the leaf blades and stems of C. ciliaris. The plant parts with the highest proportion of thin-walled cells were the legume leaflets and petioles and the Z. mays stems and leaf sheaths. The walls of the cells categorized as thick-walled were thinnest (0.9 mu m) in L, perenne leaf blades and T. repens leaflets and thickest (2.0-2.3 mu m) in the leaf blade midribs, leaf sheaths and stems of Z. mays and in the stems and petioles of T. repens. The thinnest outer walls of epidermal cells (0.9 mu m) were recorded for the leaf blades of L. perenne. The largest cells within the categories and plant parts examined (1 100000 mu m(3)) were thin-walled cells in the stems of Z. mays. The longest cells recorded (180 mu m) were thin-walled cells in the petioles of T. repens. The thick-walled cells were particularly small (1800-2600 mu m(3)) in L. perenne leaf blades and sheaths and in T. repens leaflets. The largest thick-walled cells in the study were in the stems and petioles of T. repens. The epidermal cells of D. intortum leaflets, petioles and stems were particularly small (2000-3000 mu m(3)).