全 文 ：第 25卷　第1 期　　　　　　　　　　　　　植　　　物　　　研　　　究 2005 年　1 月
Vol.25　No.1　　　　　　　　　　　　BULLETIN OF BOTANICAL RESEARCH Jan., 　2005
Foundat ion item:Supported by the State Key Basic Research and Development Plan of China(G19990160)
Author int roduction:Zu Yuangang(1954—), Ph.D., Professor , major in plant science.
Received date:2004-12-25
植物叶片愈伤组织形成的可能机制
祖元刚　于景华　唐中华　孟庆焕
(东北林业大学森林植物生态学教育部重点实验室 , 哈尔滨　150040)
摘　要　分析了植物叶片在组培条件下形成愈伤组织的过程。文中提出 ,培养基配方中的酸性物
质使植物叶片处于酸性环境中并导致植物正常细胞首先发生细胞壁酸性降解 ,随后出现原生质体
脱离细胞壁 ,进一步发生细胞器重组或细胞重建 ,人工培养基的酸性环境使细胞壁强制性地降解
后 ,植物原生质体失去细胞壁的包被后直接处于较酸性的环境中 ,可能会促使原生体出现酸性快
速分裂。因此 ,植物细胞壁是控制植物细胞完成正常细胞周期的信号载体 。
关键词　愈伤组织;形成机制;细胞壁;酸性降解
Possible mechanisms involved with the formation of leaf callus
ZU Yuan-Gang　YU Jing-Hua　TANG Zhong-Hua　MENG Qing-Huan
(Key Laboratory of Forest Plant Ecology , Ministry of Education , P.R.China , Harbin　150040)
Abstract　This paper attempted to illustrate the mechanisms of callus formation of plant leaf.The theory was
proposed that the acid material in the culture medium maintained the plant leaf in the acid environment , and
this led to fast degradation of cell wall , breaking away of protoplast from the cell wall.These free protoplasts
will aggregation into callus , without fixed organization and functions and being ready to recombine or rebuild
for the further differentiation.The acid condition in the culture medium played the most important role in the
dedifferentiation of leaves and in the formation of callus , during this course plant cell wall was presumed to
serve as signal carrier controlling the cell to finish the normal cell s cycle , not only as the inactive coat of
cells.
Key words　formation of callus;mechanism;cell wall;acid degradation
During the course of plant tissue culture , the part
of leaf explants which were connected with culture medi-
um dedifferentiates and forms callus at first.It stems
from explants but has an obvious difference to explants
and it has already lost the specific functions , ultimately
coming in being cell group with basically unanimous ex-
ternal configuration
[ 1 ,2] .Up to now , there were few re-
ports discussing the involved mechanisms of callus for-
mation.By amounts of observations and experiments ,
the theory was put forward about the possible mechanism
and course of callus formation in specific culture medium
as follow.The induction of cell wall degradation by acid
condition is the first step to any kinds of tissue cells
such as epidermis , palisade and spongy.The degrada-
tion makes it possible that protoplast escapes from cell
and then some cell organelles like nucleus and chloro-
plast starts to recombine and rebuild with nuclear as the
configuration centre.At last , the mother cells with the
ability of fast division were observed to form with simple
protoplasm membrane and cell wall and these cells will
change into callus with further development.
Acid environment conferred by culture medium was
the most significant factor for dedifferentiation from so-
matic cell to callus cell[ 3～ 5] .For example , WPM pre-
scription contains Potassium dihydrogen phosphate ,
Nicotinic acid , Amino acetic acid and 1-Naphthyl acetic
acid (NAA)and so on , which control pH of culture
medium at 5.8 ～ 6.0.Acidification will induce the ex-
pression of expanded proteins , which makes the cell wall
relaxed.On the other hand , acid environment also can
ignite productions of pectinases or cellulase to hydrolysis
cellulose molecule into glucose
[ 4～ 6] .These activities
will result in transformation of cell walls from fixed coat
to be characteristic of softening , liquid and homogeniza-
tion , making disappear of cell walls , partly or totally ,
escaping of protoplast and recombination of organelle
[ 7] .
This phenomenon or course was called acid degradation
of plant cell wall.
The above mentioned acid degradation happens not
only in the course of tissue culture , but also in the sepa-
ration and cultivation of the protoplast.Despite of well-
known knowledge in this course , there is one very im-
portant question people often ignore that plant cell wall
may serve as signal carrier controlling accomplishment
normal cell cycle[ 8] .Generally speaking , the value of
pH in the microenvironment of normal plant cell should
be obviously much higher than the culture in the normal
life state , preventing cell wall from acid degradation and
maintain the normal transduction of signal from cell wall
and plasm membrane to nuclear
[ 9 , 10] .However , due to
the acidification of culture medium , the cell wall de-
grades easily with protoplast exposure to acid environ-
ment without the protection of cell wall , and this is the
reason of fast division of protoplast.
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