Auxin and red light in the control of hypocotyl hook opening in beans

Evidence is presented to support the suggestion that endogenous auxinlike substances participate in controlling the unbending of the hypocotyl hook of Phaseolus vulgaris L. (cv. Black Valentine). An acidic indole was detected in hook diffusates by fluorometry; triiodobenzoic acid, an inhibitor of auxin transport, prevented red light-induced unbending, and indoleacetic acid can be substituted for tissue just above the elbow region as an inhibitor of opening. Indoleacetic acid also stimulated growth of shank cells, and red light increased the sensitivity of this tissue to the hormone. A small red light-induced stimulation of auxin transport through the inside half of the hypocotyl shank was observed and may be related to light-induced unbending of the hook.     

Far red light control of elongation in light-grown bean hypocotyl: Effect on different age zones and interaction with indole-3-acetic acid

The effect of far red light on the light-grown bean hypocotyland its interaction with indole-3-acetic acid (IAA) were studied.Elongation of younger zones of the hypocotyl was inhibited butthat of older zones was promoted by far red light. This wascontrolled by phytochrome. Both the hook and shank portionscould receive far red light and its effect could be transmittedto either portions of the hypocotyl. When IAA was applied to the upper cut surface of the hypocotylunit, elongation of the shank portion was promoted even withoutfar red irradiation. IAA did not change the aspect of the growthcurves but amplified the elongation of each zone. When IAA wasapplied to each zone of the shank portion, elongation of zonesolder than the treated one was promoted but that of youngerzones was inhibited. This effect was emphasized by far red light.When IAA was applied to the older shank portion, elongationof the treated zone was synergistically promoted by IAA andfar red light, but when applied to the elbow or younger shankportion, far red light completely nullified the promoting effectof IAA. (Received October 1, 1979; )     

Stimulation by Ethylene of Axis and Hypocotyl Growth in Bean and Cocklebur Seedlings

Effects of ethylene on the elongation of bean (Phaseolus vulgaris) embryonic axes and hypocotyls, and of cocklebur (Xanthium pennsylvanicum) hypocotyls were studied. In the bean axes, exogenous ethylene was promotive in stimulating longitudinal growth during the early germination period, but thereafter it turned inhibitive. This transition of the ethylene action is likely involved in the appearance of newly differentiated tissues in the hypocotyl, which are negatively sensitive to the gas. The ethylene stimulated elongation of the axes was hardly affected by light or by the presence of the cotyledons. In the bean hypocotyl segment unit, elongation was stimulated by ethylene in its limited zone, when the concentration of ethylene and the exposure times to ethylene were adequate (0.3 to 30 μl/l, 6 to 8 h): Elongation in the much younger region near to the elbow was inhibited by ethylene treatment, whereas the treatment of the upper region of the shank with ethylene finally resulted in significantly increased growth as compared to the untreated controls. In the continuing presence of ethylene over 3 days, the elongation of every region was retarded markedly and radial growth was induced in most regions of the shank from just below the elbow. These ethylene responses occurred independently of red light irradiation, but the ethylene promotion of elongation was lost by shortening the segment height, by removing the hook portion from the segment unit, or with its natural disappearance as a result of ageing. Fundamentally, similar effects of ethylene was observed in cocklebur hypocotyls.     

A fluorescence histochemical study of the monoamine-containing cell in the developing frog taste organ

Summary Sequential changes in the monoamine-contianing cell (MC cell) of the developing frog tongue has been studied by fluorescence histochemistry using uptake of 5,6-dihydroxytryptamine. At st. 16, a few yellow fluorescent cells, here called MC cells, appeared in random order at the uppermost layer of the dorsal epithelium. They were round or elliptical in shape. At st. 18 the MC cells, greatly transformed, were found at the periphery of the sensory disc primordium which first appears during this stage. The MC cell was made up of three parts: perikaryon, process and terminal portion. The perikaryon was located at the upper half of the epithelium and from it a single process stretched vertically toward the basal lamina, above which the dilated terminal portion was found. Thereafter the perikaryon gradually moved toward the basal layer while remaining at the periphery of the disc primordium. Meanwhile the terminal portion moved over the basal lamina toward the center of the disc primordium. At st. 22, the whole of the MC cell lay flat above the basal lamina. The perikaryon was localized at the periphery of the sensory disc and from there the process stretched toward the center. Thus, the morphology of MC cells resembled the adult state, except for smaller size. MC cells were never observed in the subepithelial connective tissue in the present study. This seems to suggest that the MC cell of the frog fungiform papilla is of epithelial origin.     

Cellular and subcellular localization of calcium in gravistimulated oat coleoptiles and its possible significance in the establishment of tropic curvature

Light—and electron-microscopic studies of the distribution of calcium in gravitropically responding oat (Avena sativa L. cv. “Garry”) coleoptiles are described. A modification of the antimonate precipitation procedure was used to localize tissue calcium in situ. An accumulation of Ca in the upper halves of horizontal, gravistimulated coleoptiles is seen within 10 min of stimulus onset. A pronounced redistribution of Ca to the upper side occurs within 30 min; although the localization of this cation is not uniform along the organ axis and in the apical region, Ca appears to accumulate along the lower side. The observed asymmetric distribution of Ca in these tissues precedes large-scale visible bending by 20–30 min, but is temporally well-correlated with differential growth responses in the coleoptile, as measured by more sensitive quantitative techniques. Gravitropic curvature is well developed by 3 h and is accompanied by further redistribution of Ca to tissues along the upper coleoptile half, centered around the bend. Ultrastructural localization studies indicate that Ca asymmetry results primarily from changes in the distribution of Ca within the apoplastic compartment. Large amounts of Ca accumulate at the cuticle in epidermal cell walls and in the walls of the underlying parenchyma cells at the upper side of the organ in the region of maximal bending. The differential growth response resulting in the establishment of gravitropic curvature may largely be the consequence of antagonistic effects of Ca on auxin-mediated cell wall loosening and elongation growth processes at the upper side of the organ.     

Gravitropism in Higher Plant Shoots : VI. Changing Sensitivity to Auxin in Gravistimulated Soybean Hypocotyls

Although the Cholodny-Went model of auxin redistribution has been used to explain the transduction phase of gravitropism for over 60 years, problems are apparent, especially with dicot stems. An alternative to an auxin gradient is a physiological gradient in which lower tissues of a horizontal stem become more sensitive than upper tissues to auxin already present. Changes in tissue sensitivity to auxin were tested by immersing marked Glycine max Merrill (soybean) hypocotyl sections in buffered auxin solutions (0, 10⁻⁸ to 10⁻² molar indoleacetic acid) and observing bending and growth of upper and lower surfaces. The two surfaces of horizontal hypocotyl sections responded differently to the same applied auxin stimulus; hypocotyls bent up (lower half grew more) in buffer alone or in low auxin levels, but bent down (upper half grew more) in high auxin. Dose-response curves were evaluated with Michaelis-Menten kinetics, with auxin-receptor binding analogous to enzyme-substrate binding. V_max for the lower half was usually greater than that for the upper half, which could indicate more binding sites in the lower half. K_m of the upper half was always greater than that of the lower half (unmeasurably low), which could indicate that upper-half binding sites had a much lower affinity for auxin than lower-half sites. Dose-response curves were also obtained for sections `scrubbed' (cuticle abraded) on top or bottom before immersion in auxin, and `gravitropic memory' experiments of L. Brauner and A. Hagar (1958 Planta 51: 115-147) were duplicated. [1-¹⁴C]Indoleacetic acid penetration was equal into the two halves, and endogenous plus exogenously supplied (not radiolabeled) free auxin in the two halves (by gas chromatography-selected ion monitoring-mass spectrometry) was also equal. Thus, differential growth occurred without free auxin redistribution, contrary to Cholodny-Went but in agreement with a sensitivity model.     

Defense response of resistant host Impatiens balsamina to the parasitic angiosperm Cuscuta japonica

The response of the stem of a resistant host (Impatiens baslamina) to infection by the parasitic flowering plant Cuscuta japonica was studied with light and electron microscopy. The intra- and interfascicular cambial cells in the host stem first reacted to the penetrating upper haustorium by dividing, and the differentiation of the host xylem (vascular) tissues proceeded toward interfascicular areas from vascular bundles. When the host vascular tissue was invaded by the endophyte (haustorial portion in the host stem), the host xylem was displaced, and host vessels became occluded with parenchyma cells, resulting in tyloses. As the parasitism progressed, areas of the host stem penetrated by the endophyte became swollen via secondary growth and cell division in the parenchymatous cortex, pith, and interfascicular areas. During this intrusion by the endophyte, darkly stained necrotic reactions were detected at the interface between the host tissue and the invading endophyte. The results suggested that in the host tissues penetrated by the parasite, the formation of secondary tissue and swellings caused by active cell division of ground tissue and host vessel occlusion by tyloses constitute the host structural defense against the parasite.     

Corolla tube formation in four species of solanaceae

Corolla tube formation inSolanum nigrum, Salpichroa rhomboidea, Datura stramonium var.chalybea andNicotiana tabacum cv. Xanthi nc was investigated anatomically. InSolanum, the formation of the lower portion of the corolla tube, including the portion below the stamen insertion and the inserted zones, begins with the extension of the bases of the petal primordia toward the interprimordial regions. The extension of the petal bases is caused by the successive incorporation of the interprimordial regions just beside the bases into the petal primordia by means of the upward growth at those regions. The extending petal bases reach the lower portions of stamen primordia and connect with them resulting in formation of a short tube, which later develops into the lower portion of a corolla tube accompanied by epipetalous stamens. The petal bases extend further, and connect with each other outside the stamen primordia. The upward growth occurs also at the connected regions resulting in formation of the upper portion of a corolla tube. Marginal meristems of the petal primordium differentiate not later than the connection of petal bases. After the connection, marginal meristems and meristems of connected regions become continuous with each other and develop in a similar pattern. In the other three species, the corolla tube is formed in a similar manner as in the species mentioned above. However, the connection of the petal primordia occurs much earlier than the differentiation of their marginal meristems. InSalpichroa andNicotiana, the developmental patterns of the connected region and the corolla lobe margin are different.     

Unique responses of respiration,growth, and non-structural carbohydrate storage in sink tissue of conifer seedlings to an elevation gradient at timberline

The role of carbon balance, and particularly carbon sinks, to forest boundaries and climate responses is a major question in forest ecophysiology. At timberline, low-temperature limitations on carbon-sink processes of stem and especially root tissue have been implicated in hypotheses of the upper range limits to tree distributions. Studies on carbon sinks in root and stem tissue of trees at timberline typically report variation in only one carbon sink, such as either growth, respiration, or non-structural carbohydrates (NSCs). However, these carbon sinks may differ in their response to elevation. We asked how three carbon-sink processes in root and stem tissue (i.e. all tissue below the crown of needles) change in conifer seedlings growing from the lower (2450 m) to the upper (3000 m) edges of the timberline ecotone throughout their first growth season. We repeatedly measured respiration (mg⁻¹ and individual⁻¹), growth (relative growth rates [RGR] and biomass), and NSCs in root and stem tissue of Abies lasiocarpa and Pseudotsuga menziesii.RGR of root and stem tissue were less at the upper compared to lower elevation, but only for the first few weeks of the growing season. Total biomass of root and stem tissue was generally less at the upper site, apparently due to low early season RGR, but ultimately did not significantly differ between sites by the end of the growing season. Unlike growth, respiration rates (mg⁻¹) did not differ between elevations during any period of the growing season. Nevertheless, total respiration of CO₂ from root and stem tissue (individual⁻¹) was 22% less at the upper site, which was attributable to less biomass. NSCs of root and stem tissue, specifically starch, were overall greater at the upper site, particularly for A. lasiocarpa at the end of the season, which did not parallel spatiotemporal trends in growth or respiration. The differences in seasonal trends and the effects of elevation on carbon sinks indicate a degree of independence or uncoupling of growth, respiration, and NSCs of root and stem tissue, which is not commonly appreciated in hypotheses about physiological limitations for trees at timberline.     

Effect of cell movement by random mixing between the surface and bottom of photobioreactors on algal productivity

Effect of algae movement, as a result of random mixing, between the surface and bottom zones of shallow, moderately deep and deep photobioreactors (incident light intensities per unit volume were 8125, 4062 and 2031 μmol·m⁻³·s⁻¹, respectively) on the reactor productivity was investigated. The results showed that at low cell concentrations, movement of cells between the surface and bottom zones of shallow and moderately deep reactors had no significant effect on Chlorella pyrenoidosa C-212 growth and productivity. However, as the cell concentration in the reactors increased, cell movement between the two zones resulted in increased productivity of the shallow reactor but decreased productivity of the moderately deep reactor. On the other hand, in the deep reactor, random movement of cells between the two zones resulted in decreased Chlorella growth rate regardless of the cell concentration. This may be attributed to the fact that at high cell concentration or in a deep reactor, if the cells move between the surface and bottom of the reactor, they spend too long a time in the dark part of the reactor where there is no cell growth, and endogenous respiration as well as cell death may lead to a decrease in cell concentration. When Spirulina platensis M-135 cells were cultivated in the deep reactor, even at high cell concentration, movement of cells between the surface and bottom zones of the reactor led to an increase in the reactor productivity. The reasons for the difference in the results obtained with these two strains of algae could be attributed to the difference in their light requirements since it was found that the saturation light intensity and specific decrease in cell concentration when incubated in the dark were lower for Spirulina than for Chlorella cells.     

Influence of manganese deficiency and toxicity on isoprenoid syntheses

Twenty-eight day old wheat (Triticum aestivum L. cv Stacy) response to varying Mn concentration (10.1-10,000 micromolar) in nutrient solution was measured. Manganese concentrations in the most recently matured leaves (blade 1) were 0.21 to 19.03 mmol Mn per kilogram dry weight, respectively. Fresh and dry weights increased to a maximum at the 5 micromolar Mn nutritional level (0.37 millimole Mn per kilogram dry weight) and were decreased at Mn above and below this concentration. Blade 1 chloroplast pigment concentrations increased up to the 20 micromolar Mn nutritional level (1.98 millimole Mn per kilogram dry weight) and decreased at higher Mn concentrations. Thylakoid Mn content was above 1 mole Mn/100 mole chloroplast at Mn nutrition levels which resulted in greatly decreased plant growth. Total phytoene biosynthesis was decreased by Mn deficiency and toxicity. In vitro ent- kaurene synthesis was greatly influenced by Mn concentration with a maximal biosynthesis at 1 micromolar Mn and decreases at Mn levels above and below this concentration. In vivo blade 1 gibberellic acid equivalent concentrations were maximal at 20 parts per million Mn nutrition solution levels (1.98 millimole Mn per kilogram dry weight) and decreased at Mn tissue concentrations above and below this value; additionally, gibberellic acid concentrations were reciprocal to extracted C₂₀ alcohol concentrations. Mn influence on gibberellin and chloroplast pigment biosyntheses exactly matched the measured changes in growth.     

Influence of Corn Residue Harvest Management on Grain,Stover, and Energy Yields

Economic, environmental, and energy independence issues are contributing to rising fossil fuel prices, petroleum supply concerns, and a growing interest in biomass feedstocks as renewable energy sources. Potential feedstocks include perennial grasses, timber, and annual grain crops with our focus being on corn (Zea mays L.) stover. A plot-scale study evaluating stover removal was initiated in 2008 on a South Carolina Coastal Plain Coxville/Rains–Goldsboro–Lynchburg soil association site. In addition to grain and stover yields, carbon balance, greenhouse gas (GHG) emissions and soil quality impact reported elsewhere in this issue, variation in gross energy distribution within various plant fractions — whole plant, below ear shank (bottom), above ear shank (top), cob, as well as leaves and stems of the bottom and top portions (n _{(part, year)}?=?20) was measured with an isoperibol calorimeter. Stalks from above the ear shank were the most energy dense, averaging 18.8 MJ/kg db, and when combined with other plant parts from above the ear shank, the entire top half was more energy dense than the bottom half — 18.4 versus 18.2 MJ/kg db. Gross energy content of the whole plant, including the cob, averaged 18.28?±?0.76 MJ/kg db. Over the 4 years, partial to total removal (i.e., 25 % to 100 %) of above-ground plant biomass could supply between 30 and 168 GJ/ha depending upon annual rainfall. At 168 GJ/ha, the quantity of corn stover biomass (whole plant) available in a 3,254-km² area (32 km radius) around the study site could potentially support a 500-MW power plant.     

The effect of alterations in the physical state of the membrane lipids on the ability of Acholeplasma laidlawii B to grow at various temperatures

The physical state of the membrane lipids, as determined by fatty acid composition and environmental temperature, has a marked effect on both the temperature range within which Acholeplasma laidlawii B cells can grow and on growth rates within the permissible temperature ranges. The minimum growth temperature of 8 °C is not defined by the fatty acid composition of the membrane lipids when cells are enriched in fatty acids giving rise to gel to liquid-crystalline membrane lipid phase transitions occurring below this temperature. The elevated minimum growth temperatures of cells enriched in fatty acids giving rise to lipid phase transitions occurring at higher temperatures, however, are clearly defined by the fatty acid composition of the membrane lipids. The optimum and maximum growth temperatures are also influenced indirectly by the physical state of the membrane lipids, being significantly reduced for cells supplemented with lower melting, unsaturated fatty acids. The temperature coefficient of growth at temperatures near or above the midpoint of the lipid phase transition is 16 to 18 $\text{kcal}\text{mol}$, but this value increases abruptly to 40 to 45 $\text{kcal}\text{mol}$ at temperatures below the phase transition midpoint. Both the absolute rates and temperature coefficients of cell growth are similar for cells whose membrane lipids exist entirely or predominantly in the liquid-crystalline state, but absolute growth rates decline rapidly and temperature coefficients increase at temperatures where more than half of the membrane lipids become solidified. Cell growth ceases when the conversion of the membrane lipid to the gel state approaches completion, but growth and replication can continue at temperatures where less than one tenth of the total lipid remains in the fluid state. An appreciable heterogeneity in the physical state of the membrane lipids can apparently be tolerated by this organism without a detectable loss of membrane function.     

In vivo formation steps of the hard alpha-keratin intermediate filament along a hair follicle: evidence for structural polymorphism

Several aspects of the intermediate filaments' molecular architecture remain mysterious despite decades of study. The growth process and the final architecture may depend on the physical, chemical, and biochemical environment. Aiming at clarifying this issue, we have revisited the structure of the human hair follicle by means of X-ray microdiffraction. We conclude that the histology-based growth zones along the follicle are correlated to the fine architecture of the filaments deduced from X-ray microdiffraction. Our analysis reveals the existence of two major polymorph intermediate filament architectures. Just above the bulb, the filaments are characterized by a diameter of 100 Angstroms and a low-density core. The following zone upwards is characterized by the lateral aggregation of the filaments into a compact network of filaments, by a contraction of their diameter (to 75 Angstroms) and by the setting up of a long-range longitudinal ordering. In the upper zone, the small structural change associated with the tissue hardening likely concerns the terminal domains. The architecture of the intermediate filament in the upper zones could be specific to hard alpha-keratin whilst the other architecture found in the lower zone could be representative for intermediate filaments in a different environment.     

Cohort migration of carcinoma cells: differentiated colorectal carcinoma cells move as coherent cell clusters or sheets.

Active migration of tumor cells is usually assessed as single cell locomotion in vitro using Boyden chamber-type assays. In vivo, however, carcinoma cells, malignant cells of epithelial origin, frequently invade the surrounding tissue as coherent clusters or nests of cells. We have called this type of movement "cohort migration". In our work, the invasion front of colon carcinomas consisted of compact tumor glands, partially resolved glands or markedly resolved glands with scattered tumor cell clusters or single cells lying ahead. In the former two types, which constituted about a half of all cases, cohort migration seems to be the predominant mechanism, whereas both cohort migration and single cell locomotion may be involved in the last one. In this light, it is very advantageous to investigate the mechanisms involved in the cohort migration. In this review, we present a two-dimensional motility assay as a cohort migration model, in which human colorectal carcinoma cells move outwards from the cell islands mainly as localized coherent sheets of cells when stimulated with 12-O-tetradecanoylphorbol-13-acetate (TPA) or hepatocyte growth factor/scatter factor (HGF/SF). Within the migrating cell sheets, wide intercellular gaps occur at the lower portion of the cells to allow the cells to extend leading lamellae forward while close cell-cell contacts remain at the upper portion of the cells. This localized modulation of cell-cell adhesion at the lower portion of the cells is associated with increased tyrosine phosphorylation of the E-cadherin-catenin complex in TPA-induced cohort migration and with reduced alpha-catenin complexed with E-cadherin in HGF/SF-induced cohort migration. Furthermore, fibronectin deposited by migrating cells is essential for their movement, and on the gelatin-coated substrate even degradation and remodeling of the substrate by matrix metalloproteinases are also needed. Thus, in cohort migration it is likely that cells are released from cell-cell adhesion only at the lower portion of the cells via modulation of E-cadherin-catenin-based mechanism, and this change allows the cells to extend leading lamellae onto the extracellular matrix substrate remodeled by deposition of fibronectin and organized digestion.     

Roots of willow (Salix viminalis L.) show marked tolerance to oxygen shortage in flooded soils and in solution culture

Responses to soil flooding and oxygen shortage were studied in field, glasshouse and controlled environment conditions. Established stools ofSalix viminalis L., were compared at five field sites in close proximity but with contrasting water table levels and flooding intensities during the preceding winter. There was no marked effect of site on shoot extension rate, time to half maximum length or final length attained. When rooted cuttings were waterlogged for 4 weeks in a glasshouse, soil redox potentials quickly decreased to below zero. Shoot extension was slowed after a delay of 20 d, while, in the upper 100 mm of soil, formation and outgrowth of unbranched adventitious roots with enhanced aerenchyma development was promoted after 7 d. At depths of 100–200 mm and 200–300 mm, extension by existing root axes was halted by soil flooding, while adventitious roots from above failed to penetrate these deeper zones. After 4 weeks waterlogging, all arrested root tips recommenced elongation when the soil was drained; their extension rates exceeding those of roots that were well-drained throughout. Growth in fresh mass was also stimulated. The additional aerenchyma found in adventitious roots in the upper 100 mm of soil may have been ethylene regulated since gas space development was inhibited by silver nitrate, an ethylene action inhibitor. The effectiveness of aerenchyma was tested by blocking the entry of atmospheric oxygen into plants with lanolin applied to lenticels of woody shoots of plants grown in solution culture. Root extension was halved, while shoot growth remained unaffected. H Lambers Section editor     

Analysis of growth during light-induced hook opening in cress

Abstract. Growth in various regions of the hypocotyls of dark-grown cress seedlings before and after exposure lo continuous white light has been analysed by time-lapse photography. In the dark, growth in the hook was minimal, the upward growth of the seedling being sustained by extension of the shank, especially the uppermost zones. Following irradiation, the hook and the remainder of the hypocotyl showed dissimilar growth responses. Previously growing regions of the shank were inhibited while zones within the hook, especially the apical end of the inner (concave) side, showed marked growth stimulation. These changes in growth rates commenced within 1 h from exposure to the light stimulus and thus considerably preceded any observable changes in hook angle.     

Cell Division and Expansion and Resultant Tissue 3

By following the movement of carbon particle markers on theexposed surface of a cultured tomato apex it has been shownthat a leaf primordium is formed by growth on the flank of theapex raising the tissue upwards and outwards to form the leafbuttress. The whole of the apical surface is in an active stateof cell division and expansion except in the axillary regionabove the primordium. The data provide direct estimates of therates of division in the outer layer of cells. The distribution of blocked metaphase figures following treatmentwith colchicine, shows that in the early stages of primordiumformation cell divisions are concentrated in what appears tobo a ‘growth centre’ in the corpus to one side ofthe apical dome. As the bulge of the primordium develops, thegrowth centre spreads out and splits into two parts continuingthe growth of the dome (proximal side) and the primordium (distalside). Between these two regions of active division there arisesa small pocket of cells in the axil, whose rate of divisionrapidly declines. Cuts made in the apical surface in the early stages of primordiumformation immediately gape widely, apparently as a result ofpressure exerted on the outer layers from within by divisionsin the corpus. Once the upper surface of the primordium becomesraised above the dome, the axillary cells seem to become compressedbetween the two zones of active division. In the axil at thisstage (a) cuts do not gape but close up after exuding cell sapand (b) the carbon particle markers move slightly together.     

Tissue and cellular morphological changes in growth plate explants under compression

The mechanisms by which mechanical loading may alter bone development within growth plates are still poorly understood. However, several growth plate cell or tissue morphological parameters are associated with both normal and mechanically modulated bone growth rates. The aim of this study was to quantify in situ the three-dimensional morphology of growth plate explants under compression at both cell and tissue levels. Growth plates were dissected from ulnae of immature swine and tested under 15% compressive strain. Confocal microscopy was used to image fluorescently labeled chondrocytes in the three growth plate zones before and after compression. Quantitative morphological analyses at both cell (volume, surface area, sphericity, minor/major radii) and tissue (cell/matrix volume ratio) levels were performed. Greater chondrocyte bulk strains (volume decrease normalized to the initial cell volume) were found in the proliferative (35.4%) and hypertrophic (41.7%) zones, with lower chondrocyte bulk strains (24.7%) in the reserve zone. Following compression, the cell/matrix volume ratio decreased in the reserve and hypertrophic zones by 24.3% and 22.6%, respectively, whereas it increased by 35.9% in the proliferative zone. The 15% strain applied on growth plate explants revealed zone-dependent deformational states at both tissue and cell levels. Variations in the mechanical response of the chondrocytes from different zones could be related to significant inhomogeneities in growth plate zonal mechanical properties. The ability to obtain in situ cell morphometry and monitor the changes under compression will contribute to a better understanding of mechanisms through which abnormal growth can be triggered.