【摘要】 用P³²研究了水培5—7天小麦初生根不分枝部分的吸收区问题,并用画线法确定生长区,用石蜡切片确定各区解剖结构,目的在于使离子的吸收和积累的资料与细胞的生长分化状态尽可能联系起来。与此同时,研究了时间的进程,DNP的影响,在停止供应P³²后各根段间离子的内部调配,以及局部供应P³²时各根段P³²的分布情况。主要结果如下:1.在历次实验中,沿根的长度P³²的积聚表现出两个最高点:第一高峰相应于用画线法所确定的生长区（或稍前一些）;第二高峰相应于根毛发生区。也观察到了Steward（1954）所报导的第一高峰不规则出现的情况。2.两个高峰区获取或保持P³²的性质是不相同的:1)第一高峰在根接触P³²溶液后两分钟即已出现;随时间的延长,才出现第二高峰;时间愈长,第二高峰愈明显。2)DNP处理后,第一高峰区及第二高峰区的脉冲数分别降低了49%和30%。3)于吸收P³²半小时后停止供应,使已吸收的P³²在各段间重新分配。发现P³²随着时间的增加而向第一高峰集中;但在第二高峰区P³²有向溶液中排出的情况。4)局部供应P³²的实验。分别从0—3毫米、0—10毫米和0—30毫米供给P³²,2小时后检查P³²在整条根各区的分布。发现在三种不同处理中,第一高峰区的脉冲数相同,而在第二高峰区则以浸没部分较长者脉冲数较高。认为第二高峰区的P³²一部分由第一高峰区运送,另一部分来自于该区的直接吸收。3.根据实验结果,我们认为由胚性细胞开始延长到细胞延长终止的区域（即画线法所确定的生长区）是根吸收最活跃的区域。更多还原

【Abstract】 Although much has been done concerning the absorbing zone of the root,there is an obvious diversity of opinions among different workers.The present work is undertaken to obtain more critical clata on this problem. The unbranched portions of the primary roots of 5—7 day old wheat seedlings cultured in tap water were used as experimental material.Radioactive phosphorus was used as tracer.Besides the usual radioactivity counting technique,the roots were marked with Indian ink at 1 mm intervals to ascertain the growing zone.Paraffin sections were made to observe the anatomical structures.It was hoped that by correlating physiological functions of different segments with its morphological structures,some insight may be obtained on the mode of ion absorption.The following results were obtained: 1. In nearly all experiments,the radioactivity distribution curve showed two distinct maxima.The first accumulation maximum occurred at 0—3 mm from the tip,corresponding morphologically to the growing region of the root in which the embryonic cells of the root tip were elongating.The second accumulation maximum was located at nearly 10 mm from the tip,corresponding to the region where root hairs originated. 2. The location of the first maximum showed some variation,appearing at 0—1 mm or 2—3 mm from the apex （Fig.1 A & B）.Similar phenomenon had been reported by Steward with Narcissus roots.The explanation for this variation remains to be sought. 3. The two maxima differed physiologically in the following way: 1) The first maximum appeared 2 minutes after the roots had been exposed to the solution,the second one appeared later and became more pronounced as time went on （Fig.2）. 2) 2,4-dinitrophenol inhibited the first maximum to a greater extent than it did the second one （Fig.4）. 3) After the roots were removed from the P³² solution to distilled water,the preaccumulated P³² underwent redistribution within different sections of the root.The first maximum rose higher with time,while the second maximum lost radioactivity markedly （Fig.3）. 4) When P³² was supplied locally at the 0—3 mm,0—10 mm or 0—30 mm sections of the root,the radioactivity counts at the first maximum of the three different treatments were very close together,while the counts at the second maximum deviated considerably. It was considered that the second maximum was of double origin,i.e.,partly from the migration of P³² from the first maximum （Fig.5） and partly from the direct absorption by that zone. The results lead to the belief that the growing region of the root （the region just behind the meristematic region） is most concerned with the initial absorption of P³².更多还原