Effect of drought stress on bending stiffness in petioles of Caladium bicolor (Araceae)

Abstract

• Premise of the study: Cell turgor plays an important role in the mechanical stability of herbaceous plants. This study on petioles of Caladium bicolor 'Candyland' analyzes the correlation between fl exural rigidity and cell turgor. The results offer new insights into the underlying form-structure-function relationship and the dependency of mechanical properties from water availability.• Methods: Bending modulus E of petioles is calculated from two-point bending tests, taking into account the tapering mode. The corresponding turgor of parenchyma cells during wilting is investigated by pressure probe tests.• Key results: Wilting petioles show highly signifi cant lower values of E than petioles with suffi cient water supply. These differences are also found when comparing well-watered petioles to drought-stressed petioles having parenchyma turgor values in the same range. These results indicate an additional mechanical system sensitive to drought stress. On the basis of analyses of the contribution of different petiolar tissues toward the axial second moment of area and by using experimentally determined and literature values of E for the different tissues, we were able to (1) recalculate E of the intact petiole and to compare it with experimental data and (2) quantitatively estimate the importance of the different tissues for fl exural rigidity and E of the petiole.• Conclusions: Our results show that the decrease in fl exural rigidity of petioles of Caladium bicolor 'Candyland' during wilting results from (1) a water-loss-induced decrease in mechanical effi ciency of collenchyma fi bers and (2) turgor loss of parenchyma cells.

Impact behaviour of freeze-dried and fresh pomelo ( Citrus maxima ) peel: influence of the hydration state

“…Freeze-drying of biological (plant) tissues not only removes the water from the protoplast by ice sublimation but also the amorphous cell wall matrix is dehydrated, inducing glass transition, which renders the formerly ‘rubbery’ and viscoelastic cell wall ‘glassy’ and more elastic. Water thus has a severe impact on the mechanical properties of the peel parenchyma, which are mainly governed by the cell wall properties and the turgor pressure [ 22 , 23 ]. The latter results from the protoplast, which is filled with an incompressible and highly viscous fluid, the cell sap, exerting hydrostatic pressure against the cell wall.…”

How water availability influences morphological and biomechanical properties in the one-leaf plantMonophyllaea horsfieldii

“…Between subsequent bending tests, all plants were stored at 22.9°C and 59.6% RH (mean values of laboratory conditions). The structural bending modulus for tapered beams was calculated as described in [ 24 ]; for more details, see also electronic supplementary material, appendix S1.…”

Drooping of Gerbera flower heads: mechanical and structural studies of a well-known phenomenon

“…changes in flexural rigidity) of plant organs are always based on changes in their geometry and anatomy and/or on changes of the mechanical properties of the respective tissues and cells [2], which are known to react differently to water content fluctuations [3][4][5]. In the context of the water-dependent flexural rigidity of plant organs, the turgor-dependent hydraulic properties of parenchymatous tissues and collenchyma fibres play a major role [3,6]. Moreover, the mechanical properties of lignified strengthening tissues vary depending on their moisture content [7].…”