Pod classification and its role in rubber vine (Cryptostegia grandiflora) germination and emergence
F.F. Bebawi and J.R. McKenzie, Tropical Weeds Research Centre, Queensland Department of Natural Resources, PO Box 187, Charters Towers, Queensland 4820, Australia.
Summary
A method for classifying seed pods of the woody weed rubber vine (Cryptostegia grandiflora (Roxb.) R.Br.) was developed as an aid for evaluating the effect of imposed control techniques on seed stored in pods. Rubber vine pods were qualitatively classified into four classes: juvenile, immature, mature and ripe. Pod characteristics and seed behaviour within the four designated classes were assessed to determine whether they displayed distinct characteristics.
Pod features measured were fresh weight (FWT), dry weight (DWT), relative water content (RWC), dorsal length (DL), dorsal width (DW) and dorsi-ventral width (DVW). Both seed germination and seedling emergence were assessed for seeds from each of the pod classes. Four out of the six pod characteristics (FWT, RWC, DL, DVW) differed significantly from one another. Seeds from mature and ripe pods averaged 99% germination compared with 13.7 and 0.3% for immature and juvenile pods respectively. Similarly, seedling emergence of mature and ripe pods averaged 92%, with both juvenile and immature pods averaging less than 2%. Mean germination and seedling emergence rates increased with seed maturity stage.
Plant Protection Quarterly (1999) 14 (1) 30-34.