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Plant bud dormancy is a state in
which the bud is temporarily stagnant in growth and development due to signals from neighboring tissues or their internal and external environments.
According to the different sources of signals, they are divided into paradormancy, endodormancy, and ecodormancy
.
Among them, dormancy-like refers to the state in which the bud is affected by signals from neighboring organs or tissues and develops
slowly.
Inhibition of lateral bud germination due to apical dominance is a typical dormancy-like state, regulated
by auxin synthesis of apical buds.
The mixed buds of many deciduous fruit trees, including pears, form in the summer and autumn of the previous year, after which they remain dormant without germination, and then enter the inner dormancy to overwinter, and do not germinate until the following spring
.
In the cultivation of pears in the south, the biological and abiotic stress in summer will cause some varieties to fall leaves early, resulting in the dormancy of the buds being broken and germinating, showing the phenomenon of flowering and leaf expansion in autumn (Figure 1), which not only consumes the nutrients of the tree, but also leads to a decrease in the amount of flowers and fruit production in the following spring, which has become an urgent problem
to be solved in production.
which the bud is temporarily stagnant in growth and development due to signals from neighboring tissues or their internal and external environments.
According to the different sources of signals, they are divided into paradormancy, endodormancy, and ecodormancy
.
Among them, dormancy-like refers to the state in which the bud is affected by signals from neighboring organs or tissues and develops
slowly.
Inhibition of lateral bud germination due to apical dominance is a typical dormancy-like state, regulated
by auxin synthesis of apical buds.
The mixed buds of many deciduous fruit trees, including pears, form in the summer and autumn of the previous year, after which they remain dormant without germination, and then enter the inner dormancy to overwinter, and do not germinate until the following spring
.
In the cultivation of pears in the south, the biological and abiotic stress in summer will cause some varieties to fall leaves early, resulting in the dormancy of the buds being broken and germinating, showing the phenomenon of flowering and leaf expansion in autumn (Figure 1), which not only consumes the nutrients of the tree, but also leads to a decrease in the amount of flowers and fruit production in the following spring, which has become an urgent problem
to be solved in production.
Figure 1.
Comparison of bud germination after undecimated leaves (left) and early deciduous (right).
This process involves the regulatory mechanism
of dormant in fruit tree buds.
However, this process is different
from the typical dormancy-like regulation model, the top-edge advantage regulation process.
In the apical dominance model, the removal of apical tissue can relieve lateral bud dormancy, while the post-leaf dormancy release process is not limited to lateral buds, but occurs simultaneously in both apical buds and lateral buds
.
In particular, the short fruiting spur is an important fruiting site in the arza fruit tree, and the top buds on them germinate after early leaf fall (Figure 2
).
This unique budding characteristic reveals that the process of early deciduous budding dormancy is not mainly regulated by the apical tissue, but is affected by the leaf, which is difficult to explain
with the traditional theory of apical superiority.
Therefore, the process of leaf regulation of bud dormancy can be used as a model different from the top advantage of dormancy-like research, and its mechanism needs to be further explored
.
Figure 2.
The top buds of the short fruit branches of the pear germinate after early deciduous
Recently, Professor Teng Yuanwen's team from Zhejiang University published a research paper entitled "Early defoliation induces auxin redistribution, promoting paradormancy release in pear buds" on Plant Physiology, which elucidated the mechanism of early deciduous auxin redistribution in buds and stem segments, thereby promoting the dormancy of buds
。
In this study, the process of early leaf deciduous was simulated by artificial leaf removal, and combined with tissue sections and scanning electron microscopy, leaf picking accelerated the morphological differentiation process of flower buds, and then promoted early germination of buds
.
In this process, the auxin content in the flower buds was stable, but through immunofluorescence localization, it was found that the auxin outlet carrier protein PpyPIN1b was polarly distributed on the cell membrane, and the auxin content in the stem segment at the base of the flower bud was increased, indicating that leaf picking led to the auxin tended to be exported from the flower bud, reduced the auxin concentration in the meristem of the flower bud, and promoted the germination
of the flower bud.
Transcriptome analysis using the flower buds after artificial leaf picking detected significant changes in auxin metabolism, transport and signal transduction pathway genes, which further verified the key role
of auxin in this process.
Changes in transcription levels of other hormone-related genes, such as cytokinin and monocle goldenolide, suggest that these hormones may also be involved in regulating bud out-of-season germination
caused by early leaf deciduous.
In addition, external application of the auxin analogue naphthaleneacetic acid at a high concentration (300mg/L) can inhibit the germination of buds, and the effect
of high concentration auxin inhibition dormancy relief is verified.
In this process, high concentrations of naphthaleneacetic acid inhibited the expression of PpyPIN1b and the accumulation of its protein on the cell membrane, resulting in hindrance of auxin excretion in buds, thereby inhibiting bud germination
.
Figure 3.
Pattern of regulation of early leaf deciduous induced bud autumn germination process
The above results show that early leaf deciduous can trigger auxin redistribution, reduce the content of auxin in buds, and promote the release of dormancy
in top buds and side buds.
This process is not influenced by auxin, which is derived from the apical tissue in the traditional apical advantage, but is affected by leaf action
.
This new model is proposed to help to deeply understand the regulation mechanism of annual periodic growth of perennial woody plants, and to provide a theoretical basis
for inhibiting the bud out-of-season germination caused by early leaf deciduous.
Professor Teng Yuanwen's research group is doctoral student Wei Jia as the first author
of the paper.
The paper was completed
under the guidance of Professor Teng Yuanwen, researcher Bai Songling and Associate Researcher Ni Junbei.
Professor Teng Yuanwen is the corresponding author, and researcher Bai Songling is the co-senior author
.
The team has graduated Dr.
Yang Qinsong (now working at Beijing Forestry University), doctoral student Gao Yuhao, and graduated master Tang Yinxin participated in the research work
.
The research was supported
by the National Modern Agricultural Industry Technology System Pear System Special Fund (CARS-28).
Paper link: https://doi.
org/10.
1093/plphys/kiac426
