鴨舌草無休眠種子的發芽條件

Germination Conditions for the Non-dormant Seeds of Monochoria vaginalis

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6mm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5x10-3 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0.4cm以內不影響發芽，埋土0.4至1.6cm之內時，隨深度的增加發芽率略為遞減。埋土深度在2cm以上時幾乎不發芽。水勢在-0.2MPa以上時不影響發芽，-0.2至-1.2 MPa之內時隨水勢的降低發芽率略為遞減。水勢在-0.9 MPa以下時不發芽。無休眠鴨舌草種子在22-32°C之間的發芽率皆高，在此範圍外發芽率下降，發芽的最高及最低溫分別約為40及14°C。發芽速率的最適、基礎及高端溫度分別為30.4、12.7及65.8°C。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。

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 x 10-3 mol/m2/day. No inhibition on germination 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°C . Minimum and maximum temperature for germination were approximately 14 and 40°C, respectively. Base, optimum and ceiling temperatures of the rate of germination were 12.7, 30.4 and 65.8°C 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.