A Technique for Controlling Matric Suction on Filter Papers Used in Germination Tests, Imbibition, Root and Shoot Growth Studies

Abstract

Moist filter papers are widely usedfor seed gennination tests but their water confent and matric suction are not usually controlled. A technique for controlling filter paper matric suction is described and usedfor germination studies involving fresh and aged sorghum seed (Sorghummcolor (L) Moench). Filter papers wetted to matric suctions of 0.1 ,land 10 kPa were used to study germination, root and shoot growth rate offour cultivars (M35-1, ICSV-1l2, CSH-9 & CSH-ll) of sorghum at 25°C. Time to germination, root and shoot growth were all affected by the increase in matric suction from either 0.1 to 1, or 1 to 10 kPa. Root and shoot emergence ratefrom seeds, decreased with increasing matrie suction. The increase in matric suction resulted in significant reductions (P= O. 05) in final root and shoot length. Final germination percentage was not affected by variation§ in matric suction. Ageing delayed shoot emergence. Seedlings with emetged shoots were significantly fewer at 10 kPa as compared to 1 kPa only for aged seed, and for all cultivars except Icsv-i 12. A link between matrie suction, seed-liquid contact area and the rate of water uptake by seed is demonstrated. We conclude from this study: that changes in the matric suction on filter paper even at the wet end will cause variations in gennination rate and therefore ought to be controlled during germination tests. Seed tests separated in time and space can not be compared iffilter paper matric suction is not controlled.

Keywords: Filter paper matric suction, Germination test, Seed-liquid contact area, Seed
vigour, Sorghum