Allelopafhic potential of purple nutsedge (Cyperus rotundus L.) and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] on corn (Zea mays L.). III. Influence of pH and the concentration of extracts on germination

Abstract

The influence of pH and the concentration of aqueous extracts of purple natsedge (Cyperus rotundus L.) and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] on corn (Zea mays L. cv. Tainung No. 1) germination was investigated. To examine the pH effect, full strength (x) extracts and double distilled water (control) were adjusted to pH of 6.1, 5.7, 5.4, 5.1, 4.8 and 4.5 with gydrochloric acid and sodium hydroxide. It showed that germination percentage of corn sodium bydroxide. It showed that germination percentage of corn was reduced when pH of the extracts were decreased, especially at pH of 4.5. Since the germination of corn seeds treated with weed extracts was lower than that of double distilled water treatment at the same pH, the results suggested that the differnces of extract concentration may also be involved. To study the influence of the concentration, vull strength extracts were diluted to five concentration levels, i.e., x, 1/2x, 1/4x, 1/8x and 1/16x, at pH of 5.7. It was found that both the mximal germination percentage and the germination rate were affected by the changes of the concentration of the weed extracts. The results also indicated that extracts of barnyard-grass were more suppressive than extracts of purple nutsedge on corn germination. 本文試驗旨在以香附子(Cyperus rotundus L.)與裨隼[Echinochloa crus-galli (L.) Beauv.]之2°C/1天植株萃取液，進行酸鹼值及濃度對萃取液相剋效應之探討。根據試驗結果，降低萃取液之酸鹼值減少玉米種子發芽百分比，惟改變萃取液酸鹼值從pH6.1至pH4.8對玉米僅造成低於5%以內的差異；當酸鹼值降至pH4.5或以下時，酸鹼值對玉米種子發芽之效應將超過濃度者。其次，由於在相同酸鹼值下處理雜草萃取液之玉米發芽百分比均低於處理予蒸餾水之對照組，顯然地除了酸鹼值之外，雜草萃取液中之其它因子（如萃取液浪度）亦對玉米發芽產生抑制作用。萃取液濃度的變化，係影響玉米發芽速率及最高發芽百分比。總此结果顯示，香附子與稗草萃取液之相剋效應乃由萃取液之酸鹼值及濃度所引起。同時，稗草植株萃取液較香附子對玉米發芽呈現明顯抑制作用。