摘要
【目的】重力对植物生长发育、形态建成、生理代谢等生物学过程发挥着重大作用,重力条件改变会诱导植物发生一系列生长与定向的变化。大部分木本植物在响应重力条件改变时,形成层活动会不均衡增加从而形成偏心生长的应力木,木质部结构和细胞壁成分发生明显变化。单子叶植物一般没有形成层,不能进行径向次生生长,且维管束多为散生。为了探究单子叶植物对重力的响应过程和结构变化,本文以玉米为研究对象,分析其响应重力的动态过程和形态结构变化;并通过与木本植物进行比较,揭示它们重力响应的差异。为进一步研究单子叶植物(如竹子等)及其他林木的重力反应提供一定借鉴。【方法】以玉米B73自交系为试验材料,待幼苗发育至10叶期,将试验植株水平放倒,对照植株保持直立。利用延时拍摄记录玉米重力响应过程的动态变化及变化的时间节点。通过组织切片观察和特异染色,分析发生重力响应的茎节产生的结构及细胞壁成分的变化。【结果】以第1片旗叶着生的节作为第1茎节,从下往上依次标记茎节。重力改变后玉米的响应过程及变化如下:1)响应过程:玉米从顶端向下依次感应重力作用。植株放倒10 h后开始响应重力,在之后的20 h内,植株从顶端到第4茎节先后向上弯起,直至植株与水平面呈90°角到达终止状态。2)形态变化:多次重复试验显示只有第4、5、6茎节发生明显的形态变化,在靠近节的近地侧部位出现不同程度的组织膨大。通过纵切观察,3个茎节膨大部位的组织和内部导管呈向上弯曲的状态。对照植株相应茎节并未发生改变。3)维管束结构变化:与对照相比,近地侧维管束的细胞数量增多并呈纺锤形,细胞壁极显著变薄且没有明显的导管组织;远地侧维管束的细胞数量和细胞壁厚度因生长状态不同而变化不一。第4茎节变化最显著。4)维管束细胞壁成分变化:分别用木质素特异染料间苯三酚和纤维素染料卡尔科弗卢尔荧光增白剂(calcofluor white)对试验组和对照组的横切切片进行染色,结果显示:近地侧维管束细胞壁的木质素含量较少,而纤维素含量比对照增多;远地侧维管束细胞壁成分与对照相比没有明显变化。【结论】玉米在重力条件改变后迅速调整茎节延伸方向,与对照相比茎节近地侧维管束细胞数量显著增多、细胞壁变薄、木质素减少而纤维素增多。由此推测玉米受重力影响后,通过调整居间分生组织活动,产生类似应拉木、压缩木的组织,但又与二者有所区别。这可为研究重力响应下木本植物维管组织分化(木材形成)的调控提供一定基础。
【Objective】Gravity plays an important role in growth and development,in terms of morphogenesis,physiology,metabolism and other biological process in plant.The change of gravity condition will induce a series of changes in plant growth and orientation.In response to the change of gravity conditions,the activities of cambium in woody plant increase unevenly,leading to the eccentric growth of stem and the formation of reaction wood with the obvious changes of xylem structure and cell wall components.Monocotyledons have no cambium,and the stem node elongated through the activity of intermediate meristem.In order to explore the response process and structural changes of monocotyledons under gravistimulation,we use maize to analyze its dynamic process and morphological changes in response to gravistimulation.By comparing with xylophyta,the differences of gravity response between monocotyledons and xylophyta were revealed.It provides a basis for further studies on the gravity response of monocotyledonous woody plants(such as bamboo,etc.)and other trees.【Method】The inbred line B73 of maize was used to grow seedlings until 10 leaf stage,the seedlings were laid down horizontally,and the seedlings used as control were still kept upright.The dynamic changes and time points of maize gravity response process were recorded by delay photography.Through tissue sections and special staining,the changes of tissue structure and the differences of cell wall components in maize stem nodes response to gravity were analyzed.【Result】The node which the first flag leaf came from was counted as the first one,then the stem nodes were numbered from the bottom to the top.Following the gravity induction,the response processes changed as followed:1)Gravity response process:Maize plants sense the gravity from the top down subsequently.The plants began to respond to gravity 10 hours after induction.In the next 20 hours,the plants were bent up from the top to the fourth stem node successively,until the plant was perpendicular to ground that is the termination state.2)Morphology and structure:The repeated experiments showed that only the fourth,fifth and sixth stem nodes had morphological changes,where different degrees of tissue expansion occurred at the side facing ground.The tissue growth and internal vascular bundles in expanded parts of these three stem nodes showed upward bending.The corresponding stem nodes of the control plants showed normal morphology.3)Vascular bundles:Compared with the control group,the number of proximal vascular bundle cells increased and showed spindle shape,and the cell wall became significantly thinner without obvious vessel tissue,while the number of cells and the thickness of cell wall in the distal vascular bundles varied with the developmental status.In addition,the fourth internode changed most significantly.4)Cell wall components of vascular bundles:The sections of normal and experimental stem were stained with phloroglucinol and Calcofluor white respectively.The results showed that the content of lignin in the cell walls of proximal vascular bundles was low,and the content of cellulose was higher than that of the control.There was no significant content change in the cell wall of the distal vascular bundles compared with the control.【Conclusion】In response to gravity condition,maize can adjust the extension direction of stem node quickly,and cell number of the proximal vascular bundles increased dramatically.At the same time,the cell walls of the proximal vascular bundles became thinner with the content of lignin decreased but cellulose increased.Therefore,it is speculated that after responding to gravity,maize may produce tissues similar to tension wood and compressed wood by adjusting the activities of the intercalary meristem,but different from them.This study lays a foundation for the study of the regulation mechanism of vascular tissue development(wood formation)of woody plants in gravity response.
作者
贺学娇
楚立威
文爽爽
卢孟柱
唐芳
He Xuejiao;Chu Liwei;Wen Shuangshuang;Lu Mengzhu;Tang Fang(State Key Laboratory of Tree Genetics and Breeding Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration Research Institute of Forestry,Chinese Academy of Forestry,Beijing 100091;State Key Laboratory of Subtropical Silviculture Zhejiang A&F University,Hangzhou 311300;Co-Innovation Center for Sustainable Forestry in Southern China Nanjing Forestry University,Nanjing 210037)
出处
《林业科学》
EI
CAS
CSCD
北大核心
2021年第2期93-102,共10页
Scientia Silvae Sinicae
基金
国家重点研发计划项目“林木次生生长的分子调控和环境胁迫机制”(2016YFD0600100)
“万人计划”入选人才特殊支持经费。