Abstract

Effects of environmental factors on the germination of non-dormant seeds of Monochoria vaginalis (Burm. f.) Persil var. plantaginea Solms. were investigated. Under anoxia condition the seeds germinated but the subsequent seedling growth was retarded. In hypoxia condition of 6 mm submergence, the seeds germinated readily and the seedlings grew normally. Aerobic condition inhibited germination almost completely. The seeds absolutely required light to germinate. Light intensity saturated at as low as 5 × 10-3 mol/m2/day. No inhibition ongermination was found at light intensity of 3 mol/m2/day. Under waterlogged condition the seeds were prevented from germination by burying in the soil up to 4 mm depth. Percentage germination was inhibited slightly and progressively in deeper depth of soil up to 16 mm, drastically decreased thereafter. Almost no germination occurred at 20 mm depth. No effect of water potential within -0.2 MPa on germination was found. Percentage germination was decreased slightly and progressively between -0.2 to -0.8 MPa, drastically decreased thereafter. The non-dormant seeds germinated well at constant temperature ranging from 22-32 ℃. Minimum and maximum temperature for germination were approximately 14 and 40 ℃, respectively. Base, optimum and ceiling temperatures of the rate of germination were 12.7, 30.4 and 65.8 ℃ respectively. Thermal time for 50 % germination was 19.2 and 38.5 degree-day for sub-optimum and supra-optimum temperature respectively. Suitable methods and conditions for germination tests were proposed.

中文摘要

本試驗旨在探討無休眠鴨舌草種子的適當發芽條件。結果顯示該種子在無氧狀態下可以發芽，但幼苗無法生長。種子浸於水中 6 mm 的缺氧狀態下發芽甚快，幼苗生長正常。曝露於空氣中則不發芽。鴨舌草種子的發芽絕對需要光照，所需的光量相當低，每天白光照射量達 5 × 10-3 mol/m2 就已飽合。每天高達 3 mol/m2 的照射量不會抑制發芽。湛水狀況下埋於土中 0.4 cm 以內不影響發芽，埋土 0.4 至 1.6 cm 之內時，隨深度的增加發芽率略為遞減。埋土深度在 2 cm 以上時幾乎不發芽。水勢在 -0.2 MPa 以上時不影響發芽。無休眠鴨舌草種子在 22-32 ℃ 之間的發芽率皆高，在此範圍外發芽率下降，發芽率最高及最低溫分別約為 40 及 14 ℃。發芽速率的最適、基礎及高端溫度分別為 30.4、12.7 及 65.8 ℃。半數發芽所需的積溫就低於最適溫時為 19.2 度日，就高於最適溫時為 38.5 度日。根據以上的試驗結果，提出無休眠鴨舌草種子發芽試驗的方法及適當條件。

Keyword: Monochoria vaginalis, Seeds, Germination, Temperature, Light, Oxygen, Water potential, Burial depth. 鴨舌草，種子，發芽，溫度，光，氧，水勢，埋土深度。