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在上课前20多天,剪取两枝夹竹桃,去掉部分枝叶,以减少蒸腾。一枝在基部3厘米以上环割去掉一圈树皮,露出长约2厘米木质部,并刮去木质部上的形成层,作为实验枝;另一枝保持原状,作为对比枝。然后将两枝缠上纸条为瓶塞。再把枝分别悬插在同样大小、无色盛有清水的玻瓶里。瓶内要保持一定空间,放在室内有光处。可不换水,但要补充失去的水。这样就可慢慢观察到:实验枝环割以上处因得到韧皮部输导的有机养料而长出不定根,最下端因割去了韧皮部得不到有机养料就不能(或很少)生长不定根;对比枝的基部能和实验枝的环割处上部一样,生长不定根。这就证明了
More than 20 days before class, cut two oleander, remove part of the leaves to reduce transpiration. One branch at the base of 3 cm above the ring to remove a circle of bark, revealing about 2 cm xylem, and scrape off the formation of the xylem, as the experimental branch; the other remained the same as the control branch. Then wrap the two sticks for the stopper. Then sticks were hung in the same size, colorless glass filled with water. Bottle to maintain a certain space, put a light at the interior. Do not change the water, but to replenish the water lost. In this way, we can slowly observe that the branch of the experimental branch above can not (or rarely) grow adventitious roots because of the adventitious root grown by the organic nutrient fed by the phloem, and the lowermost root can not (or rarely) grow by adhering to the phloem. The base of the branch can be the same as the upper branch of the branch of the experimental branch, and adventitious roots grow. This proves