水分、溫度和氧氣為影響林木種子發芽之主要外在因子，其中種子發芽時之水分供應更為重要限制因子。本研究結果顯示，分子量6000之聚乙烯醇試液濃度在0~50gL^(-1)，之問對木麻黃種子發芽率雖不具影響之效應，但平均發芽日則甚受試液濃度之影響，且隨水勢降低而有延長之趨勢發生。
Water, temperature, and oxygen are the three main seed-germination affecting factors. Water supply, especially, is the most important limiting one. The results indicated that although polyethylene glycol (PEG 6000) solutions (0-50 g/L) show no effects on seed germination percentage of Casuarina spp., yet mean germination day showed prolonged tendency as solution concentration increased.
