Shoot Bending Research Articles

Combined influence of shoot bending and plant growth regulators on morphological traits of Guava cv. Allahabad Safeda

Combined influence of shoot bending and plant growth regulators on morphological traits of Guava cv. Allahabad Safeda

Effect of Shoot Bending at Different Time on Production and Quality of Hybrid Tea Rose Cultivar Minu Pearle

A field experiment was undertaken from September to March for two consecutive years (2020 and 2021) to find out the best time for shoot bending in Hybrid Tea rose. Growth and development of rose cultivar Minu Pearle, was significantly influenced by shoot bending at different time (4th week of September to 4th week of December). Among the treatments tallest plants & maximum leaf area was produced in plants bended on T5 whereas, the plant canopy was registered to be maximum in 2nd week of December. The highest rate of shoot elongation at 15 & 30 days after shoot bending was noted in second week of November and October respectively. Application of shoot bending on 2nd week of October recorded early blooming and slowest flower bud emergence was registered in T5whereas, delayed sepal reflex and maximum days taken to attain cup shape was observed in T6. In terms of flower quality parameters like length and diameter of flower bud and pedicel and weight of individual flower, T5 proved to be superior. Shoot bending applied on 2nd week of November (T4) produced long and thick stalks. Among the treatments maximum number of flowers, longest self and vase life, highest dry matter production from leaves and stem, greater chlorophyll and anthocyanin content was observed in T5.

Bending to auxin: fast acid growth for tropisms.

The phytohormone auxin is the major growth regulator governing tropic responses including gravitropism. Auxin build-up at the lower side of stimulated shoots promotes cell expansion, whereas in roots it inhibits growth, leading to upward shoot bending and downward root bending, respectively. Yet it remains an enigma how the same signal can trigger such opposite cellular responses. In this review, we discuss several recent unexpected insights into the mechanisms underlying auxin regulation of growth, challenging several existing models. We focus on the divergent mechanisms of apoplastic pH regulation in shoots and roots revisiting the classical Acid Growth Theory and discuss coordinated involvement of multiple auxin signaling pathways. From this emerges a more comprehensive, updated picture how auxin regulates growth.

Influence of Copper Pollution of Haplic Calcic Chernozem With Various Contents of Sand Fractions on Morphobiometric Indicators of Spring Barley

The growth and development of plants is one of the criteria for assessing the degree of soil pollution with heavy metals. Morphological and anatomical changes in test plants affected by pollutants, such as growth retardation, shoot bending, and decreased root length and mass, indicate the worsening of environmental conditions. The effect of various ratios of soil and sand polluted with copper (Cu) on morphobiometric parameters of spring barley (Hordeum sativum distichum), Ratnik variety, was studied in a model vegetative experiment. Haplic calcic chernozem was used as a substrate with different ratios of soil/sand. It was determined that an addition of sand into the soil in the amounts of 25%, 50% and 75% of soil mass resulted in the alteration of the physical properties of the chernozem, which was reflected in the morphometric parameters of the plants. The most notable changes in the parameters were observed after pollution of soil-sand substrates with Cu(CH3COO)2 in the amounts of 250 mg/kg, 500 mg/kg, 1000 mg/kg and 2000 mg/kg. The maximum growth and development retardation of the barley plants was found at the maximum content of sand and the maximum concentration of Cu. The pollutant reduced the root length and, to a lesser degree, the height of the aboveground components of the plant, which as a result, decreased the total plant biomass.
 Keywords: trace elements, soil, agricultural crops, particle size distribution

ITRAQ-based proteomic analysis of apple buds provides new insights into regulatory mechanisms of flowering in response to shoot bending

Flowering is an important life cycle stage in apple trees, and young ‘Nagafu No. 2’ produce limited inferior flower buds. Shoot bending, an effective agronomic measure, is widely used to promote flowering but little is known regarding the underlying molecular mechanisms. Using isobaric tags for relative and absolute quantification LC−MS/MS, 8,585 proteins expressed in buds during flower bud differentiation were identified. The 1,060 up- and 1,079 down-regulated proteins after shoot bending were divided into 7 pattern-based groups: I (22/5), II (30/57), III (34/21), IV (77/61), V (381/452), VI (218/170), and VII (298/313) types. Number of proteins were associated with carbohydrate, fatty acid, and lipid metabolism, as well as hormone, transcription factor, circadian rhythm, and photoperiod and flowering pathways. The differentially expressed proteins involved in fatty acid and lipid pathways were up-regulated by shoot bending, while other proteins that were involved in starch synthesis were down-regulated. In addition, circadian rhythm- and flowering-related genes were up-regulated by shoot bending. This research provides a valuable inventory of proteins involved in floral bud development and contributes to the understanding of the regulatory mechanisms of flower bud differentiation caused by shoot bending in apple trees.

Spatio-temporal kinematic analysis of shoot gravitropism in Arabidopsis thaliana.

Plant shoots can bend upward against gravity, a behavior known as shoot gravitropism. The conventional quantification of shoot bending has been restricted to measurements of shoot tip angle, which cannot fully describe the spatio-temporal bending process. Recently, however, advanced imaging analyses have been developed to quantify in detail the spatio-temporal changes in inclination angle and curvature of the shoot. We used one such method (KymoRod) to analyze the gravitropism of the Arabidopsis thaliana inflorescence stem, and successfully extracted characteristics that capture when and where bending occurs. Furthermore, we implemented an elastic spring theoretical model and successfully determined best fitted parameters that may explain typical bending behaviors of the inflorescence stem. Overall, we propose a data-model combined framework to quantitatively investigate shoot gravitropism in plants.

A mathematical model explores the contributions of bending and stretching forces to shoot gravitropism in Arabidopsis

Plant shoot gravitropism is a complex phenomenon resulting from gravity sensing, curvature sensing (proprioception), the ability to uphold self-weight and growth. Although recent data analysis and modelling have revealed the detailed morphology of shoot bending, the relative contribution of bending force (derived from the gravi-proprioceptive response) and stretching force (derived from shoot axial growth) behind gravitropism remains poorly understood. To address this gap, we combined morphological data with a theoretical model to analyze shoot bending in wild-type and lazy1-like 1 mutant Arabidopsis thaliana. Using data from actual bending events, we searched for model parameters that minimized discrepancies between the data and mathematical model. The resulting model suggests that both the bending force and the stretching force differ significantly between the wild type and mutant. We discuss the implications of the mechanical forces associated with differential cell growth and present a plausible mechanical explanation of shoot gravitropism.

Quantifying the contribution of bent shoots to plant photosynthesis and biomass production of flower shoots in rose (Rosa hybrida) using a functional-structural plant model.

Background and AimsThe success of using bent shoots in cut-rose (Rosa hybrida) production to improve flower shoot quality has been attributed to bent shoots capturing more light and thus providing more assimilates for flower shoot growth. We aimed at quantifying this contribution of photosynthesis by bent shoots to flower shoot growth.MethodsRose plants were grown with four upright flower shoots and with no, one or three bent shoots per plant. Plant architectural traits, leaf photosynthetic parameters and organ dry weight were measured. A functional–structural plant (FSP) model of rose was used to calculate photosynthesis of upright shoots and bent shoots separately, taking into account the heterogeneous canopy structure of these plants.Key ResultsBent shoots contributed to 43–53 % of total assimilated CO2 by the plant. Plant photosynthesis increased by 73 and 117 % in plants with, respectively, one and three bent shoots compared with plants without bent shoots. Upright shoot photosynthesis was not significantly affected by the presence of bent shoots. However, upright shoot dry weight increased by 35 and 59 % in plants with, respectively, one and three bent shoots compared with plants without bent shoots. The increased upright shoot dry weight was entirely due to the contribution of extra photosynthesis by bent shoots, as this was the only source that could induce differences in upright shoot growth apart from their own photosynthesis. At least 47–51 % of the photosynthesis by bent shoots was translocated to upright shoots to support their biomass increase.ConclusionsBased on model simulations, we conclude that the positive effect of shoot bending on flower shoot growth and quality in cut-rose production system can almost entirely be attributed to assimilate supply from bent shoots. FSP modelling is a useful tool to quantify the contributions of photosynthesis by different parts of heterogeneous canopies.

Optimal Design of Plant Canopy Based on Light Interception: A Case Study With Loquat.

Canopy architecture determines the light distribution and light interception in the canopy. Reasonable shaping and pruning can optimize tree structure; maximize the utilization of land, space and light energy; and lay the foundation for achieving early fruiting, high yield, health and longevity. Due to the complexity of loquat canopy architecture and the multi-year period of tree growth, the variables needed for experiments in canopy type training are hardly accessible through field measurements. In this paper, we concentrated on exploring the relationship between branching angle and light interception using a three-dimensional (3D) canopy model in loquat (Eriobotrya japonica Lindl). First, detailed 3D models of loquat trees were built by integrating branch and organ models. Second, the morphological models of different loquat trees were constructed by interactive editing. Third, the 3D individual-tree modeling software LSTree integrated with the OpenGL shadow technique, a radiosity model and a modified rectangular hyperbola model was used to calculate the silhouette to total area ratio, the distribution of photosynthetically active radiation within canopies and the net photosynthetic rate, respectively. Finally, the influence of loquat tree organ organization on the light interception of the trees was analyzed with different parameters. If the single branch angle between the level 2 scaffold branch and trunk is approximately 15° and the angles among the level 2 scaffold branches range from 60 to 90°, then a better light distribution can be obtained. The results showed that the branching angle has a significant impact on light interception, which is useful for grower manipulation of trees, e.g., shoot bending (scaffold branch angle). Based on this conclusion, a reasonable tree structure was selected for intercepting light. This quantitative simulation and analytical method provides a new digital and visual method that can aid in the design of tree architecture.

Transcription profiles reveal the regulatory mechanisms of spur bud changes and flower induction in response to shoot bending in apple (Malus domestica Borkh.).

Shoot bending, as an effective agronomic measure, has been widely used to promote flowering in 'Fuji' apple trees. Here, we examined the transcriptional responses of genes in 'Fuji' apple buds at different flowering stages under a shoot-bending treatment using RNA sequencing. A complex genetic crosstalk-regulated network, involving abscisic acid-related genes, starch metabolism and circadian rhythm-related genes, as well as stress response-related genes, was up-regulated by shoot bending, in which were contrbuted to apple flowerbud formation in response to shoot-bending conditions. Flower induction plays an important role in the apple tree life cycle, but young trees produce fewer and inferior flower buds. Shoot bending, as an effective agronomic measure, has been widely used to promote flowering in 'Fuji' apple trees. However, little is known about the gene expression network patterns and molecular regulatory mechanisms caused by shoot bending during the induced flowering. Here, we examined the transcriptional responses of genes in 'Fuji' apple buds at different flowering stages under a shoot-bending treatment using RNA sequencing. A steady up-regulation of carbon metabolism-related genes led to relatively high levels of sucrose in early induced flowering stages and starch accumulation during shoot bending. Additionally, global gene expression profiling determined that cytokinin, indole-3-acetic acid, gibberellin synthesis and signalling-related genes were significantly regulated by shoot bending, contributing to cell division and differentiation, bud growth and flower induction. A complex genetic crosstalk-regulated network, involving abscisic acid-related genes, starch metabolism- and circadian rhythm-related genes, as well as stress response-related genes, was up-regulated by shoot bending. Additionally, some transcription factor family genes that were involved in sugar, abscisic acid and stress response signalling were significantly induced by shoot bending. These important flowering genes, which were mainly involved in photoperiod, age and autonomous pathways, were up-regulated by shoot bending. Thus, a complex genetic network of regulatory mechanisms involved in sugar, hormone and stress response signalling pathways may mediate the induction of apple tree flowering in response to shoot-bending conditions.

Can greater understanding of macadamia canopy architecture lay the foundation for orchard productivity improvements?

Macadamia canopies tend to grow large and complex due to vigorous recurrent flushes of vegetative growth. New shoot growth can occur at any time of the year from apical and axillary buds, elongating existing axes and forming new axis orders, respectively. The macadamia canopy is relatively unmodified and low yielding, thus yield efficiency and management practices would benefit from an increased understanding of canopy growth dynamics and architecture. Here we detail a range of investigations into the architectural development of macadamia over different scales, and methods for modifying architecture with a view to this information being incorporated into the design of improved orchard systems. For isolated shoots we have documented the elongation of internodes and the whole growth unit (GU), and their relationship to thermal time. We have also undertaken a detailed architectural study on two cultivars of young trees leading up to their first flowering, in an attempt to compare and understand patterns of early vegetative development. At the tree scale there were no differences in canopy volume or tree height between cultivars, however, detailed scales revealed differences in canopy components such as GU number, GU length and branching patterns. Shoot bending can modify vegetative architecture and reproductive development in temperate crops, although responses in subtropical crops could be more complicated. Bending first-order shoots in macadamia reduced apical growth and induced axillary release. When shoots are bent at the time of floral initiation raceme number was increased on the first-order shoot axis, possibly due to a coincidence between bending-induced axillary bud release and time-dependent floral signals. Observing interactions between components at different scales aids understanding of the mechanisms and relationships controlling the structure and function of the growing macadamia canopy, thus providing opportunities to modify macadamia growth for the benefit of production efficiency.

Simulation of tree growth for three almond cultivars with contrasting architecture with the L-ALMOND model

The L-PEACH and L-ALMOND models use L-systems to simulate the architectural development and carbohydrate dynamics (assimilation, transport, distribution, storage and remobilization) of growing peach and almond trees, respectively. The models were able to successfully simulate tree growth and development and produce realistic estimates of tree size, structure and productivity over several years after planting, but always only for a specific cultivar. We here show how L-ALMOND can be adapted to simulate the architectural growth of three cultivars (‘Nonpareil’, ‘Aldrich’, and ‘Winters’) differing in tree architecture after three steps for each cultivar: i) inclusion of specific shoot architectures for six types of shoots (watersprouts, long, medium-long, medium, medium-short, and small shoots). Branching patterns and flowering occurrence for each type of shoot were previously assessed by developing hidden semi-Markov statistical models based on field research. Spur morphology was the same. Very different patterns emerged of sylleptic shoot production from lateral meristems on watersprouts, long, and medium-long shoots. ‘Aldrich’ and ‘Winters’ produced many more sylleptic shoots than ‘Nonpareil’. No sylleptic shoot growth appeared from medium, medium-short, and small shoots in any cultivar; ii) definition of the type of shoot derived from a sylleptic shoot. In ‘Aldrich’ and ‘Winters’ most sylleptic shoots were spurs and short shoots, respectively, while in ‘Nonpareil’ their length varied widely (spurs, small, medium-short, and medium shoots); and iii) adjustment of a parameter to modify shoot bending to simulate differences in growth habit observed in the field. ‘Aldrich’ was more erect than ‘Winters’ and ‘Nonpareil’. After modifications, L-ALMOND 3-dimensional tree simulations were similar to actual pictures of field trees, demonstrating how different shoot architectures result in different tree architectures over time, and especially the role that sylleptic shoot production plays in determining final tree architecture in almond.

Effect of bending of shoots on flowering, yield and quality of guava cv. Khaja

The study of the effect of bending of shoots in different months in guava cv. Khaja was carried out at
 Horticulture Research Station, Mondouri of Bidhan Chandra Krishi Viswavidyalaya to find out suitable bending time for improving flowering, yield and quality of guava. The experiment consists of seven treatments with three replications in a randomised block design. The different treatments were bending in October (T1), November (T2), March (T3), April (T4), May (T5), June (T6) and untreated control (T7). Bending in June (T6) resulted early emergency of new shootlet (15.0 days), flower initiation (40.33 days) and fruit set (48.33 days) from the date of bending as well as the same treatment showed maximum fruit weight (197.67 gm), fruit length (8.00 cm), fruit diameter (7.16 cm) and pulp thickness (2.20 cm). Higher fruit quality in terms of total soluble solids (11.04 0brix), total sugar (7.0 %) and ascorbic acid content (197.96 mg/100g pulp) was noted when bending was done in May (T5) and June (T6). Bending in the month of October (T1) resulted in maximum C: N ratio of leaf with maximum flowering shootlets in a branch and yield (63.67 kg/plant). So, time of bending may be standardized in the month of October or June for higher profit.

Crop regulation for round-the-year harvesting of guava

Guava (Psidium guajava L.), the poor man's apple, is one of the most common fruit grown widely in tropical and subtropical regions of the world. Guava has well established markets in more than 60 countries. The top ten guava producers in the world are India, China, Thailand, Pakistan, Mexico, Indonesia, Brazil, Bangladesh, Philippines and Nigeria. Guava bear fruits at different times of the year. However, harvesting all the crops in small amount is not profitable, In India, maximum fruiting is found in the rainy season which are poor in quality due to high water content and severely attacked by fruit fly while the winter harvested fruits are superior in quality having good market demand. Cycling of crop to avoid rainy season crop and increasing winter crop is possible. Cycling of crop by using different methods of flower regulation, it is possible to harvest guava round-the-year. The method(s) to be followed for crop regulation depend on climatic factors, cropping pattern, market and industry demand, cultivar, etc. The different methods used for crop cycling are a) water management to induce stress, b) pruning of shoots at different levels and at different times, c) training (bending) of shoots, and d) manual or chemical thinning of flowers. Spraying of different bioregulators (naphthaleneacetic acid, naphthalene acetamide, 2,4-dichlorophenoxyacetic acid, etc.), chemicals (4,6-dintro-o-cresol, potassium iodide, urea, etc.) at different concentrations were found effective in de-blossoming and regulation of cropping. Crop cycling for round-the-year harvest is possible by pruning of shoots at different times of the year. This paper will discuss the different methods of crop cycling in guava.

Phototropic bending of intact and wounded potato shoots

Intact and wounded shoots of in vitro cultured potato were investigated in situ to determine how their phototropic (PT) bending capacity was affected by water availability and exogenous auxin supplementation. Wounding strongly decreased PT bending but it recovered upon supplementation of water, auxin or both. Intact shoots required neither water nor auxin, while shoot segments required both. Shoot cuttings required only water, while, like shoot segments, decapitated shoots had a strong requirement for auxin. Water supplementation was beneficial in all treatments and PT bending was not affected in cultures that were submerged in water for a short period. Sucrose and inorganic salts present in the medium strongly affected PT bending capacity of cultures, favouring combinations with lower concentrations of both. Sucrose alone strongly promoted PT bending up to a concentration of 5%. Osmotic shock induced by the addition of small volumes of highly concentrated carbohydrate solutions (sucrose, glucose or sorbitol) induced a rapid but transient decline in PT bending capacity. These results indicate that water availability is a major factor that affects PT bending in potato plantlets.

Interaction with gravitropism, reversibility and lateral movements of phototropically stimulated potato shoots.

Phototropic (PT) and gravitropic (GT) bending are the two major tropic movements that determine the spatial position of potato shoots. We studied PT bending of potato plantlets grown under long-day photoperiods in several prearranged position setups providing different interactions with the GT response. Starting with the standard PT stimulation setup composed of unilateral irradiation of vertically positioned shoots, experiments were also done in antagonistic and synergistic setups and in treatments with horizontal displacement of the light source. In the standard setup, PT bending suppressed the GT bending, which could occur only if the PT stimulation was cancelled. The antagonistic position, with phototropism and gravitropism attempting to bend shoots in opposite directions, showed phototropism and gravitropism as independent bending events with the outcome varying throughout the day reflecting diurnal changes in the competence of individual tropic components. Whilst gravitropism was constant, phototropism had a marked daily fluctuation of its magnitude with a prominent morning maximum starting an hour after the dawn in the growth room and lasting for the next 6 h. When phototropism and gravitropism were aligned in a synergistic position, stimulating shoot bending in the same direction, there was little quantitative addition of their individual effects. The long period of morning PT bending maximum enabled multiple PT bending events to be conducted in succession, each one preceded by a separate lag phase. Studies of secondary PT events showed that potato plantlets can follow and adjust their shoot position in response to both vertical and horizontal movements of a light source. PT bending was reversible, since the 180° horizontal change of a blue light (BL) source position resulted in reversal of bending direction after a 20-min-long lag phase.Electronic supplementary materialThe online version of this article (doi:10.1007/s10265-016-0821-4) contains supplementary material, which is available to authorized users.

Crop regulation in guava cv. Sardar asinfluenced by chemicals and cultural practices under semi arid conditions of Rajasthan

A field experiment was conducted at Instrumental Farm, Department of Horticulture, Rajasthan College of Agriculture, Udaipur. The experiment consisted of 8 treatments comprising chemicals (Urea @ 10% and 15% foliar spray, NAA @ 1000 ppm) and cultural practices (pruning at 75 % and 50 % intensity, bending of shoots, withholding of irrigation water) were applied during the course of investigation. These treatments were evaluated under randomized block design with 4 replications by adopting uniform cultural schedule during the experimentation. The results revealed that all treatments had significant increase in vegetative growth characteristics (number of newly emerged shoots, per cent increase in shoot growth after 30 days interval, canopy volume, PAR above and below canopy and leaf area index) physico-chemical characteristics(Fruit weight, pulp thickness, pulp: seed ratio, TSS, acidity, ascorbic acid content, total sugars and reducing sugar) and yield characteristics( per cent fruit retention, number of fruits per plant, yield per tree and yield per hectare) over the Ambe bahar and control. Among the treatments foliar spray of NAA @ 1000 ppm in the month of April (T7) significantly increase the canopy volume (371.55 m3), fruit weight (152.60 g), pulp thickness (1.13 cm), pulp seed ratio (58:90), TSS (13.80%), ascorbic acid (193.75 mg/100 gm pulp), total sugars (7.29%) and reducing sugar (4.21%) followed by application of single foliar spray of 15 per cent urea at 50 per cent bloom stage (T2). Number of fruit per plant (389.50), yield per tree (56.38 kg) estimated fruit yield (156.39 q ha-1) with higher net return (Rs.109394.88 ha-1) and B: C ratio (2.81:1) were recorded maximum in T2.

Shoot bending promotes flower bud formation by miRNA-mediated regulation in apple (Malus domestica Borkh.).

SummaryFlower induction in apple (Malus domestica Borkh.) trees plays an important life cycle role, but young trees produce fewer and inferior quality flower buds. Therefore, shoot bending has become an important cultural practice, significantly promoting the capacity to develop more flower buds during the growing seasons. Additionally, microRNAs (miRNAs) play essential roles in plant growth, flower induction and stress responses. In this study, we identified miRNAs potentially involved in the regulation of bud growth, and flower induction and development, as well as in the response to shoot bending. Of the 195 miRNAs identified, 137 were novel miRNAs. The miRNA expression profiles revealed that the expression levels of 68 and 27 known miRNAs were down‐regulated and up‐regulated, respectively, in response to shoot bending, and that the 31 differentially expressed novel miRNAs between them formed five major clusters. Additionally, a complex regulatory network associated with auxin, cytokinin, abscisic acid (ABA) and gibberellic acid (GA) plays important roles in cell division, bud growth and flower induction, in which related miRNAs and targets mediated regulation. Among them, miR396, 160, 393, and their targets associated with AUX, miR159, 319, 164, and their targets associated with ABA and GA, and flowering‐related miRNAs and genes, regulate bud growth and flower bud formation in response to shoot bending. Meanwhile, the flowering genes had significantly higher expression levels during shoot bending, suggesting that they are involved in this regulatory process. This study provides a framework for the future analysis of miRNAs associated with multiple hormones and their roles in the regulation of bud growth, and flower induction and formation in response to shoot bending in apple trees.

Phototropic responses of potato under conditions of continuous light and subsequent darkness

The phototropic (PT) bending capacity of potato plantlets in vitro was studied under conditions of continuous light (CL) and subsequent darkness (CLD). In CL, diurnal changes characteristic for the 16/8 h LD photoperiod were absent and the response, although complex, was constant at any time of the day. Graphic representation of shoot bending indicated the presence of two separate, partly overlapping PT responses. The first was a fast, time-limited process (FPR) with a 20 min lag phase and a maximum fixed at 70 min, followed by a steady bending process (SPR) starting 50–90 min after the beginning of blue light (BL) stimulation. The FPR response rapidly deteriorated in darkness and after 60–120 min it was replaced with BL augmented circumnutations. SPR was a constant feature in darkness and while both FPR and circumnutations were absent when darkness exceeded 120 min, the SPR response remained present in darkness irrespective of its duration. The abrupt end of circumnutations marked the beginning of the synchronized SPR bending response. Darkness lasting 120 min was also a pivotal point after which the PT capacity started to recover. After 8 h of CLD, the PT capacity was fully restored. The FPR response reappeared at dawn when the light was turned on. Potato plantlets also manifested fast solar tracking movements, correcting shoot position in relation to the horizontal displacement of the BL source. Solar tracking movements contrary to circumnutations comprised shoot torsion twisting (twining). Our results demonstrate that, in potato shoots, multiple PT responses are present and operational simultaneously.

Tree shoot bending generates hydraulic pressure pulses: a new long-distance signal?

When tree stems are mechanically stimulated, a rapid long-distance signal is induced that slows down primary growth. An investigation was carried out to determine whether the signal might be borne by a mechanically induced pressure pulse in the xylem. Coupling xylem flow meters and pressure sensors with a mechanical testing device, the hydraulic effects of mechanical deformation of tree stem and branches were measured. Organs of several tree species were studied, including gymnosperms and angiosperms with different wood densities and anatomies. Bending had a negligible effect on xylem conductivity, even when deformations were sustained or were larger than would be encountered in nature. It was found that bending caused transient variation in the hydraulic pressure within the xylem of branch segments. This local transient increase in pressure in the xylem was rapidly propagated along the vascular system in planta to the upper and lower regions of the stem. It was shown that this hydraulic pulse originates from the apoplast. Water that was mobilized in the hydraulic pulses came from the saturated porous material of the conduits and their walls, suggesting that the poroelastic behaviour of xylem might be a key factor. Although likely to be a generic mechanical response, quantitative differences in the hydraulic pulse were found in different species, possibly related to differences in xylem anatomy. Importantly the hydraulic pulse was proportional to the strained volume, similar to known thigmomorphogenetic responses. It is hypothesized that the hydraulic pulse may be the signal that rapidly transmits mechanobiological information to leaves, roots, and apices.