Xylem-Phloem Exchange Via the Rays: The Undervalued Route of Transport

木质部 韧皮部 植物 化学 生物物理学 生物
作者
Aart J. E. van Bel
出处
期刊:Journal of Experimental Botany [Oxford University Press]
卷期号:41 (6): 631-644 被引量:234
标识
DOI:10.1093/jxb/41.6.631
摘要

The radial solute exchange between xylem and phloem is an important determinant of the nutrient distribution and C/N economy of seed plants. Nevertheless, our knowledge of the mechanism of xylem-phloem exchange is very limited. This paper aims to integrate anatomical and physiological data about xylem-phloem exchange and focuses on the mechanisms of radial transport. Electrophysiological mapping and intracellular injection of fluorescent dyes demonstrate that stem tissue is organized in symplastic subunits specialized in either longitudinal or lateral transport. Radial orientation, anatomical and physiological organization, strong metabolic activities, relatively negative membrane potentials, and high capacities of uptake make the rays the most likely routes for symplastic xylem-to-phloem transport. Parallel apoplastic transport may occur through radial canacules between the ray cells. The symplastic xylem-to-phloem transport includes a number of steps: (a) passage across the vessel/parenchyma interface, (b) transfer in the ray, and (c) delivery from the ray into the sieve tube/companion cell complex. Large contact pits in the vessel walls give access to the ray cells, by which the solutes are accumulated through substrate/proton co-transport. Dense pitting on the tangential walls and other ultrastructural features suggest preferential symplastic transport in the radial direction. Auxiliary endo/exocytosis is under dispute. The transport step from the ray to the sieve tube/companion cell complex remains to be elucidated. In phloem-to-xylem transport, the unloading from the phloem along the stem is essentially apoplastic, but under specific conditions it may be symplastic. Further transfer to the xylem probably occurs via the symplastic route through the ray. During radial transport, important metabolic interconversions take place into either transport or storage compounds. In many trees, the metabolism of the ray cells undergoes cyclic, annual fluctuations. Complex season-bound deposition/mobilization processes in the ray cells corresponding with seasonal changes in membrane permeability and cellular organization, reflect a master-system designed to co-ordinate the C/N economy throughout the year.
最长约 10秒,即可获得该文献文件

科研通智能强力驱动
Strongly Powered by AbleSci AI
更新
PDF的下载单位、IP信息已删除 (2025-6-4)

科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
薄雪草完成签到,获得积分10
2秒前
大橙子发布了新的文献求助10
2秒前
快乐学习每一天完成签到 ,获得积分10
2秒前
薄荷味完成签到 ,获得积分0
4秒前
科研通AI2S应助笑林采纳,获得10
4秒前
无心的雅旋完成签到,获得积分10
5秒前
量子星尘发布了新的文献求助10
6秒前
Horizon完成签到 ,获得积分10
10秒前
Oliver完成签到 ,获得积分10
12秒前
Superman完成签到 ,获得积分10
15秒前
Tina酱完成签到 ,获得积分10
15秒前
琪琪完成签到,获得积分10
15秒前
双碳小王子完成签到,获得积分10
17秒前
smottom应助科研通管家采纳,获得10
19秒前
19秒前
明时完成签到,获得积分10
20秒前
杨瑞东完成签到 ,获得积分10
23秒前
yyyy完成签到,获得积分10
31秒前
缥缈的平卉完成签到 ,获得积分10
32秒前
量子星尘发布了新的文献求助10
43秒前
李爱国应助大橙子采纳,获得10
44秒前
magictoo发布了新的文献求助30
50秒前
52秒前
yang完成签到,获得积分10
52秒前
Minicoper发布了新的文献求助10
53秒前
快乐丸子完成签到,获得积分10
54秒前
简单而复杂完成签到,获得积分10
54秒前
大橙子发布了新的文献求助10
58秒前
张牧之完成签到 ,获得积分10
1分钟前
冷冷暴力完成签到,获得积分10
1分钟前
YYY完成签到,获得积分10
1分钟前
1分钟前
gujian完成签到 ,获得积分10
1分钟前
帅气的秘密完成签到 ,获得积分10
1分钟前
自然函发布了新的文献求助10
1分钟前
冰冰双双完成签到,获得积分10
1分钟前
开心夏旋完成签到 ,获得积分0
1分钟前
我要读博士完成签到 ,获得积分10
1分钟前
活泼的大船完成签到,获得积分10
1分钟前
AFF完成签到,获得积分10
1分钟前
高分求助中
【提示信息,请勿应助】关于scihub 10000
Les Mantodea de Guyane: Insecta, Polyneoptera [The Mantids of French Guiana] 3000
徐淮辽南地区新元古代叠层石及生物地层 3000
The Mother of All Tableaux: Order, Equivalence, and Geometry in the Large-scale Structure of Optimality Theory 3000
Handbook of Industrial Diamonds.Vol2 1100
Global Eyelash Assessment scale (GEA) 1000
Picture Books with Same-sex Parented Families: Unintentional Censorship 550
热门求助领域 (近24小时)
化学 材料科学 医学 生物 工程类 有机化学 生物化学 物理 内科学 纳米技术 计算机科学 化学工程 复合材料 遗传学 基因 物理化学 催化作用 冶金 细胞生物学 免疫学
热门帖子
关注 科研通微信公众号,转发送积分 4038128
求助须知:如何正确求助?哪些是违规求助? 3575831
关于积分的说明 11373827
捐赠科研通 3305610
什么是DOI,文献DOI怎么找? 1819255
邀请新用户注册赠送积分活动 892655
科研通“疑难数据库(出版商)”最低求助积分说明 815022