Pulvinus
Gravitropism
Gravitation
Gravity Sensing
Plant Stems
Plant Growth Regulators
Gibberellins
Transient and sustained increases in inositol 1,4,5-trisphosphate precede the differential growth response in gravistimulated maize pulvini. (1/24)
The internodal maize pulvinus responds to gravistimulation with differential cell elongation on the lower side. As the site of both graviperception and response, the pulvinus is an ideal system to study how organisms sense changes in orientation. We observed a transient 5-fold increase in inositol 1,4,5-trisphosphate (IP3) within 10 s of gravistimulation in the lower half of the pulvinus, indicating that the positional change was sensed immediately. Over the first 30 min, rapid IP3 fluctuations were observed between the upper and lower halves. Maize plants require a presentation time of between 2 and 4 h before the cells on the lower side of the pulvinus are committed to elongation. After 2 h of gravistimulation, the lower half consistently had higher IP3, and IP3 levels on the lower side continued to increase up to approximately 5-fold over basal levels before visible growth. As bending became visible after 8-10 h, IP3 levels returned to basal values. Additionally, phosphatidylinositol 4-phosphate 5-kinase activity in the lower pulvinus half increased transiently within 10 min of gravistimulation, suggesting that the increased IP3 production was accompanied by an up-regulation of phosphatidylinositol 4, 5-bisphosphate biosynthesis. Neither IP3 levels nor phosphatidylinositol 4-phosphate 5-kinase activity changed in pulvini halves from vertical control plants. Our data indicate the involvement of IP3 and inositol phospholipids in both short- and long-term responses to gravistimulation. As a diffusible second messenger, IP3 provides a mechanism to transmit and amplify the signal from the perceiving to the responding cells in the pulvinus, coordinating a synchronized growth response. (+info)Hormonal and gravitropic specificity in the regulation of growth and cell wall synthesis in pulvini and internodes from shoots of Avena sativa L. (oat). (2/24)
Segments can be cut from the peduncular-1 internode of oat (Avena sativa L.) shoots so as to contain the graviresponsive leaf-sheath pulvinus and gibberellin-sensitive internodal tissue. Incorporation of [14C]glucose was used to monitor cell wall synthesis in these two tissues as affected by gravistimulus, indoleacetic acid (IAA), gibberellic acid (GA3), and fusicoccin (FC). Pulvinar cell wall synthesis was promoted by IAA and FC (both within about 1 h), as well as by gravistimulus (starting between 3 and 6 h), whereas GA3 had no effect on nongravistimulated pulvini. In contrast, GA3 and FC promoted internodal cell wall synthesis (initiated between 1 and 2 h), whereas IAA and gravistimulus caused a decrease in internodal uptake. FC preferentially promoted incorporation into the matrix component of the wall in both tissues. Gravistimulus failed to increase responsiveness of pulvinar tissue to IAA, whereas GA3 partially overcame gravistimulus-promoted incorporation into pulvinar cell wall, probably because of preferential movement of label into the rapidly elongating internode. The results demonstrate that these eight stimulus/tissue combinations can be examined easily in an isolated 10-mm stem segment, providing new opportunities for the comparative study of tissue- and stimulus-specific events in gene regulation and signal transduction in agronomically important cereals. (+info)Effect of dark pretreatment on the kinetics of response of barley pulvini to gravistimulation and hormones. (3/24)
Starch in pulvinus amyloplasts of barley (Hordeum vulgare cv Larker) disappears when 45-day-old, light-grown plants are given 5 days of continuous darkness. The effect of this loss on the pulvinus graviresponse was evaluated by following changes in the kinetics of response during the 5-day dark period. Over 5 days of dark pretreatment, the lag to initial graviresponse and the subsequent half-time to maximum steady state bending rate increased significantly while the maximum bending rate did not change. The change in response to applied indoleacetic acid (100 micromolar) plus gibberellic acid (10 micromolar) without gravistimulation, under identical dark pretreatments, was used as a model system for the response component of gravitropism. Dark pretreatment did not change the lag to initial response following hormone application to vertical pulvini, but both the maximum bending rate and the half-time to the maximum rate were significantly reduced. Also, after dark pretreatment, significant bending responses following hormone application were observed in vertical segments with or without added sucrose, while gravistimulation produced a response only if segments were given sucrose. These results indicate that starch-filled amyloplasts are required for the graviresponse of barley pulvini and suggest that they function in the stimulus perception and signal transduction components of gravitropism. (+info)Localization and pattern of graviresponse across the pulvinus of barley Hordeum vulgare. (4/24)
Pulvini of excised stem segments from barley (Hordeum vulgare cv Larker') were pretreated with 1 millimolar coumarin before gravistimulation to reduce longitudinal cell expansion and exaggerate radial cell enlargement. The cellular localization and pattern of graviresponse across individual pulvini were then evaluated by cutting the organ in cross-section, photographing the cross-section, and then measuring pulvinus thickness and the radial width of cortical and epidermal cells in enlargements of the photomicrographs. With respect to orientation during gravistimulation, we designated the uppermost point of the cross-section 0 degrees and the lowermost point 180 degrees. A gravity-induced increase in pulvinus thickness was observable within 40 degrees of the vertical in coumarin-treated pulvini. In upper halves of coumarin-treated gravistimulated pulvini, cells in the inner cortex and inner epidermis had increased radial widths, relative to untreated gravistimulated pulvini. In lower halves of coumarin-treated pulvini, cells in the central and outer cortex and in the outer epidermis showed the greatest increase in radial width. Cells comprising the vascular bundles also increased in radial width, with this pattern following that of the central cortex. These results indicate (a) that all cell types are capable of showing a graviresponse, (b) that the graviresponse occurs in both the top and the bottom of the responding organ, and (c) that the magnitude of the response increases approximately linearly from the uppermost point to the lowermost. These results are also consistent with models of gravitropism that link the pattern and magnitude of the graviresponse to graviperception via statolith sedimentation. (+info)Cell wall and enzyme changes during the graviresponse of the leaf-sheath pulvinus of oat (Avena sativa). (5/24)
The graviresponse of the leaf-sheath pulvinus of oat (Avena sativa) involves an asymmetric growth response accompanied by several asymmetric processes, including degradation of starch and cell wall synthesis. To understand further the cellular and biochemical events associated with the graviresponse, changes in cell walls and their constituents and the activities of related enzymes were investigated in excised pulvini. Asymmetric increases in dry weight with relatively symmetric increases in wall weight accompanied the graviresponse. Starch degradation could not account for increases in wall weight. However, a strong asymmetry in invertase activity indicated that hydrolysis of exogenous sucrose could contribute significantly to the increases in wall and dry weights. Most cell wall components increased proportionately during the graviresponse. However, beta-D-glucan did not increase symmetrically, but rather increased in proportion in lower halves of gravistimulated pulvini. This change resulted from an increase in glucan synthase activity in lower halves. The asymmetry of beta-D-glucan content arose too slowly to account for initiation of the graviresponse. A similar pattern in change in wall extensibility was also observed. Since beta-D-glucan was the only wall component to change, it is hypothesized that this change is the basis for the change in wall extensibility. Since wall extensibility changed too slowly to account for growth initiation, it is postulated that asymmetric changes in osmotic solutes act as the driving factor for growth promotion in the graviresponse, while wall extensibility acts as a limiting factor during growth. (+info)Altered growth response to exogenous auxin and gibberellic acid by gravistimulation in pulvini of Avena sativa. (6/24)
Pulvini of excised segments from oats (Avena sativa L. cv Victory) were treated unilaterally with indoleacetic acid (IAA) or gibberellic acid (GA3) with or without gravistimulation to assess the effect of gravistimulation on hormone action. Optimum pulvinus elongation growth (millimeters) and segment curvature (degrees) over 24 hours were produced by 100 micromolar IAA in vertical segments. The curvature response to IAA at levels greater than 100 micromolar, applied to the lower sides of gravistimulated (90 degrees) pulvini, was significantly less than the response to identical levels in vertical segments. Furthermore, the bending response of pulvini to 100 micromolar IAA did not vary significantly over a range of presentation angles between 0 and 90 degrees. In contrast, the response to IAA at levels less than 10 micromolar, with gravistimulation, was approximately the sum of the responses to gravistimulation alone and to IAA without gravistimulation. This was observed over a range of presentation angles. Also, GA3 (0.3-30 micromolar) applied to the lower sides of horizontal segments significantly enhanced pulvinus growth and segment curvature, although exogenous GA3 over a range of concentrations had no effect on pulvinus elongation growth or segment curvature in vertical segments. The response to GA3 (10 micromolar) plus IAA (1.0 or 100 micromolar) was additive for either vertical or horizontal segments. These results indicate that gravistimulation produces changes in pulvinus responsiveness to both IAA and GA3 and that the changes are unique for each growth regulator. It is suggested that the changes in responsiveness may result from processes at the cellular level other than changes in hormonal sensitivity. (+info)Do starch statoliths act as the gravisensors in cereal grass pulvini? (7/24)
To determine if starch statoliths do, in fact, act as gravisensors in cereal grass shoots, starch was removed from the starch statoliths by placing 45-day-old intact barley plants (Hordeum vulgare cv 'Larker') in the dark at 25 degrees C for 5 days. Evidence from staining with I2-KI, scanning electron microscopy, and transmission electron microscopy indicated that starch grains were no longer present in plastids in the pulvini of plants placed in the dark for 5 days. Furthermore, gravitropic curvature response in these pulvini was reduced to zero, even though pulvini from vertically oriented plants were still capable of elongating in response to applied auxin plus gibberellic acid. However, when 0.1 molar sucrose was fed to the dark pretreated, starch statolith-free pulvini during gravistimulation in the dark, they not only reformed starch grains in the starch-depleted plastids in the pulvini, but they also showed an upward bending response. Starch grain reformation appeared to precede reappearance of the graviresponse in these sucrose-fed pulvini. These results strongly support the view that starch statoliths do indeed serve as the gravisensors in cereal grass shoots. (+info)Cytoplasmic pH dynamics in maize pulvinal cells induced by gravity vector changes. (8/24)
In maize (Zea mays) and other grasses, changes in orientation of stems are perceived by pulvinal tissue, which responds to the stimulus by differential growth resulting in upward bending of the stem. The amyloplast-containing bundle sheath cells are the sites of gravity perception, although the initial steps of gravity perception and transmission remain unclear. In columella cells of Arabidopsis roots, we previously found that cytoplasmic pH (pH(c)) is a mediator in early gravitropic signaling (A.C. Scott, N.S. Allen [1999] Plant Physiol 121: 1291-1298). The question arises whether pH(c) has a more general role in signaling gravity vector changes. Using confocal ratiometric imaging and the fluorescent pH indicator carboxy seminaphtorhodafluor acetoxymethyl ester acetate, we measured pH(c) in the cells composing the maize pulvinus. When stem slices were gravistimulated and imaged on a horizontally mounted confocal microscope, pH(c) changes were only apparent within the bundle sheath cells, and not in the parenchyma cells. After turning, cytoplasmic acidification was observed at the sides of the cells, whereas the cytoplasm at the base of the cells where plastids slowly accumulated became more basic. These changes were most apparent in cells exhibiting net amyloplast sedimentation. Parenchyma cells and isolated bundle sheath cells did not show any gravity-induced pH(c) changes although all cell types responded to external stimuli in the predicted way: Propionic acid and auxin treatments induced acidification, whereas raising the external pH caused alkalinization. The results suggest that pH(c) has an important role in the early signaling pathways of maize stem gravitropism. (+info)A pulvinus is not a term that has a specific medical definition, but it is a term used in anatomy. A pulvinus refers to a small cushion-like structure, usually made up of modified muscle or nerve tissue. It is found in various parts of the body and serves to provide support, protection, or flexibility.
For example, in the eye, there are pulvinar nuclei, which are clusters of neurons located within the thalamus that play a role in visual processing. In botany, a pulvinus is a swelling at the base of a leaf petiole that helps control the movement of the leaf.
Therefore, while "pulvinus" may not have a specific medical definition, it is still a term used in anatomy and physiology to describe certain structures with similar characteristics.
Gravitropism is the growth or movement of a plant in response to gravity. It is a type of tropism, which is the growth or movement of an organism in response to a stimulus. In gravitropism, plant cells can sense the direction of gravity and grow or bend towards or away from it. Roots typically exhibit positive gravitropism, growing downwards in response to gravity, while shoots exhibit negative gravitropism, growing upwards against gravity. This growth pattern helps plants establish themselves in their environment and optimize their access to resources such as water and light.
I am not aware of a widely recognized medical definition for the term "Mimosa." In general, it may refer to a type of plant or a cocktail made with champagne and orange juice. If you are looking for information on a specific medical condition or concept, please provide more context so that I can give you a more accurate and helpful response. Is there something specific you had in mind?
'Avena sativa' is the scientific name for a type of grass species known as common oat or cultivated oat. It is widely grown as a crop for its seed, which is used as a food source for both humans and animals. Oats are rich in fiber, vitamins, minerals, and antioxidants, making them a popular choice for breakfast cereals, baked goods, and animal feeds. In addition to their nutritional value, oats have also been used in traditional medicine for various purposes, such as treating skin irritation and promoting hair growth.
I'm sorry for any confusion, but "gravitation" is not a term that is typically used in the context of medical definitions. Gravitation is a fundamental force that attracts two objects with mass towards each other. It is the force that causes objects to fall towards the earth and keeps the planets in orbit around the sun.
In the field of medicine, the concepts of gravity or gravitational forces are not directly relevant to the diagnosis or treatment of medical conditions. However, there may be some indirect applications related to physiology and human health, such as the effects of microgravity on the human body during space travel.
'Gravity sensing' is not a term typically used in medical definitions. However, in the context of physiology and neuroscience, it refers to the ability of certain cells or organisms to detect and respond to changes in gravity. This is particularly relevant in the vestibular system, which is responsible for maintaining balance and spatial orientation.
In the human body, gravity sensing in the vestibular system is achieved through the detection of head movement and position by hair cells located in the inner ear. These hair cells are embedded in a gel-like structure within the semicircular canals and the utricle and saccule of the vestibular apparatus. When the head moves, the fluid within these structures moves as well, bending the hair cells and stimulating nerve impulses that are sent to the brain. The brain then interprets these signals to help us maintain our balance and spatial orientation.
Therefore, while not a traditional medical definition, gravity sensing is an important concept in understanding how the body maintains its equilibrium and navigates through space.
A plant stem is not typically defined in a medical context, but rather in the field of botany. However, I can certainly provide a general biological definition for you.
In plants, stems are organs that serve primarily as support structures, holding leaves, flowers, and fruits aloft where they can receive sunlight and exchange gases. They also act as conduits, transporting water, nutrients, and sugars made during photosynthesis between the roots and shoots of a plant.
The stem is usually composed of three main tissue systems: dermal, vascular, and ground. The dermal tissue system forms the outermost layer(s) of the stem, providing protection and sometimes participating in gas exchange. The vascular tissue system contains the xylem (which transports water and nutrients upward) and phloem (which transports sugars and other organic compounds downward). The ground tissue system, located between the dermal and vascular tissues, is responsible for food storage and support.
While not a direct medical definition, understanding the structure and function of plant stems can be relevant in fields such as nutrition, agriculture, and environmental science, which have implications for human health.
Plant growth regulators (PGRs) are natural or synthetic chemical substances that, when present in low concentrations, can influence various physiological and biochemical processes in plants. These processes include cell division, elongation, and differentiation; flowering and fruiting; leaf senescence; and stress responses. PGRs can be classified into several categories based on their mode of action and chemical structure, including auxins, gibberellins, cytokinins, abscisic acid, ethylene, and others. They are widely used in agriculture to improve crop yield and quality, regulate plant growth and development, and enhance stress tolerance.
Gibberellins (GAs) are a type of plant hormones that regulate various growth and developmental processes, including stem elongation, germination of seeds, leaf expansion, and flowering. They are a large family of diterpenoid compounds that are synthesized from geranylgeranyl pyrophosphate (GGPP) in the plastids and then modified through a series of enzymatic reactions in the endoplasmic reticulum and cytoplasm.
GAs exert their effects by binding to specific receptors, which activate downstream signaling pathways that ultimately lead to changes in gene expression and cellular responses. The biosynthesis and perception of GAs are tightly regulated, and disruptions in these processes can result in various developmental abnormalities and growth disorders in plants.
In addition to their role in plant growth and development, GAs have also been implicated in the regulation of various physiological processes, such as stress tolerance, nutrient uptake, and senescence. They have also attracted interest as potential targets for crop improvement, as modulating GA levels and sensitivity can enhance traits such as yield, disease resistance, and abiotic stress tolerance.
A medical definition for "plant shoots" may not be readily available, as the term is primarily used in botany and horticulture. However, I can provide you with a general definition:
Plant shoots refer to the above-ground portion of a plant, which typically includes structures like stems, leaves, flowers, and buds. Shoots originate from the seed or the growing tip of the plant and are responsible for photosynthesis, nutrient absorption, and reproduction. In some contexts, "plant shoots" might also refer to new growth that emerges from an existing plant, such as when a leaf or stem sprouts a new branch or flower.
I'm happy to help! However, it seems there might be a bit of confusion here. Starch is not typically considered a medical term, but rather a nutritional and biochemical concept. Here's a brief explanation:
Starch is a complex carbohydrate that serves as the primary form of energy storage in plants. It is made up of long chains of glucose molecules and can be found in various foods such as grains, legumes, fruits, and vegetables. Amylase, an enzyme present in our saliva and digestive system, helps break down starch into simpler sugars during the digestion process so that our bodies can absorb them for energy.
I hope this clarifies any confusion! If you have any other questions or need further information on a medical topic, please don't hesitate to ask.
Pulvinus
Aspergillus pulvinus
Glossary of botanical terms
Helicia glabriflora
Nyctinasty
Acacia burkittii
Acacia dimidiata
Parkia javanica
Ochnaceae
Acacia decurrens
Acacia latescens
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Petiole (botany)
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Thigmonasty
Ulvipinara
Phyllanthaceae
Acacia scopulorum
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Paraheliotropism
Ruth Lyttle Satter
Mimosa pudica
Spruce
Pulvinar nuclei
Tsuga
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Picea chihuahuana
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Pulvinus - Wikipedia
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Petiole4
- Using nuclear magnetic resonance, upward movement of water within the pulvinus joint in response to electrical stimulation was observed in the pulvinus at the base of the petiole (=the leaf stalk). (wikipedia.org)
- A petiole is nearly always present, often with a pulvinus at its base. (wikipedia.org)
- pulvinus always present at the base of each leaflet, and usually present at base of petiole. (co.zw)
- Parts of each species (seed, stem, root, leaf, pulvinus and petiole) were sectioned after fixation and wax embedding with a LEITZ 1512 rotary microtome at 20 to 24 μm thickness and observed with a LEITZ DIAPLAN photomicroscope. (scialert.net)
Leaflets1
- 381 Pulvini may be present at the base of the leaf stalk or on its other end (apex), where the leaf is attached, or in a compound leaf at the place where the leaflets are joined to its middle stem. (wikipedia.org)
Upper3
- Movement of water to the upper or lower part of the pulvinus causes asymmetric swelling, therefore causing the stalk to either droop or rise. (wikipedia.org)
- The upper (slow elongation) and lower (fast elongation) halves of six pulvini were harvested per time point. (nih.gov)
- Pulvini from the control plants were separated into left and right halves (simulating upper and lower harvesting of pulvini in the gravity stimulated plants). (nih.gov)
Distal1
- gland near distal end of pulvinus or absent. (worldwidewattle.com)
Gland1
- gland 0-8 mm above pulvinus. (worldwidewattle.com)
Stimulation1
- Mechanical stimulation via touch is perceived and is translated to electrical stimulation causing the flow of ions out of the pulvinus cells. (wikipedia.org)
Stem1
- This motion is performed by motor cells in the pulvinus, a flexible segment of the stem just below the bud. (rarexoticseeds.com)
Petioles1
- petioles typically with distinct pulvinus at each end. (neonscience.org)
Base2
- A pulvinus (pl. pulvini) is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. (wikipedia.org)
- A pulvinus is located at the base of each leaflet of the plant. (wikipedia.org)
Cells1
- This is followed by an efflux of water, resulting in a sudden change of turgor pressure in the cells of the pulvinus. (wikipedia.org)
Long1
- glaborous, pulvinus 6-10 cm long. (seedvendor.com)
Spikelets1
- Spikelets divergent or appressed, with or without axillary pulvini. (swbiodiversity.org)
Turgor pressure3
- This is followed by an efflux of water, resulting in a sudden change of turgor pressure in the cells of the pulvinus. (wikipedia.org)
- Aquaporins on the vacuole membrane of pulvini allow for the efflux of water that contributes to the change in turgor pressure. (wikipedia.org)
- The cells that make up the pulvinus swell and shrink due to turgor pressure in accordance to the circadian clock and create the visible movement in the leaves (Zhou C, Han L, Fu C, etc. 2012). (root-houseplants.com)
Organ1
- The reversible movements involve osmotic motors in the pulvinus organ 3 , but rhythmic leaf movements can also be growth associated and thus non-reversible. (nature.com)
Bases2
- primary branches 3-6 cm, appressed to divaricate, varying sometimes within a panicle, stiff to flexible, bases appressed or abruptly spreading, usually without axillary pulvini. (swbiodiversity.org)
- The swollen leaf bases (pulvini) are densely pubescence and the buds are somewhat angular. (nybg.org)
Plant1
- Pulvini are common, for example, in members of the bean family Fabaceae (Leguminosae): 185 and the prayer plant family Marantaceae. (wikipedia.org)
Branches1
- The complex in our region can be distinguished from other species by the following characteristics: perennial bunchgrass with rolled, thread-like and often curved blades, a ligule with conspicuous hairs, panicles for the most part condensed or contracted and without axillary pulvini (small appendages in the branch axils that force branches open) and purple awns 2-5 cm or even longer, which are equal to almost equal. (swbiodiversity.org)
Flow2
- As the sun moves across the sky, different amounts of water flow into different parts of the pulvinus, nudging the leaf in the sunniest direction. (time.com)
- In spite of that fact the number of vessels containing intimal musculature, muscularelastic sphincters and polypoid pulvini in the arterial bed flow increases and in the major outflowing veins, on the contrary, thinning of their muscular tori takes place. (scirp.org)
Common1
- The irreversibility of this process is probably due to deposition of new cell wall material and decreased wall extensibility, but tissue expansion likely results from mechanisms in common with those in pulvinus tissue 6 . (nature.com)