Hypodermal Cell Walls Research Articles

The structural organization of the outer tissues in the gametophytic stem of the umbrella moss Hypnodendron menziesii optimizes load bearing.

The ultrastructural design and biochemical organization of the significantly thickened outer tissues of the gametophytic stem of Hypnodendron menziesii optimizes load bearing of the stem. Hypnodendron menziesii is a bryoid umbrella moss growing in high humid conditions on the forest floors of New Zealand. The erect gametophyte bears up to eight whorls of branches in succession, spreading across the stem that bears the heavy weight of branches with highly hydrated leaves. Our investigation using a combination of light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and TEM-immunolabeling techniques provided novel information on the structural design and biochemical organization of greatly thickened cell walls of epidermal, hypodermal, and outermost cortical tissues, comparing underlying thin-walled cortical tissues in the gametophytic stem. Probing into the ultrastructure of the cell wall architecture of these target tissues by TEM and SEM revealed the cell walls to display a multilamellar organization, in addition to demonstrating the presence of an electron-dense substance in the cell wall, presumably flavonoids. The pattern of distribution and concentration of rhamnogalacturonan, homogalacturonan, and heteromannan, as determined by immunogold labeling, suggests that it is the combination of structural and molecular design of the cell wall that may optimize the mechanical function of the epidermal, hypodermal, and outer cortical tissues. Statistical relationships between the overall thickness of epidermal, hypodermal, and outer cortical cell walls, the lumen area of cells and the percentage area of cell wall occupied in these tissues at different heights of the stem, and thickness of secondary cell wall layers (L1-L4/5) were explored. The results of these analyses unequivocally support the contribution of outer tissues to the mechanical strength of the resilient stem.

Apple fruit periderms (russeting) induced by wounding or by moisture have the same histologies, chemistries and gene expressions.

Russeting is a cosmetic defect of some fruit skins. Russeting (botanically: induction of periderm formation) can result from various environmental factors including wounding and surface moisture. The objective was to compare periderms resulting from wounding with those from exposure to moisture in developing apple fruit. Wounding or moisture exposure both resulted in cuticular microcracking. Cross-sections revealed suberized hypodermal cell walls by 4 d, and the start of periderm formation by 8 d after wounding or moisture treatment. The expression of selected target genes was similar in wound and moisture induced periderms. Transcription factors involved in the regulation of suberin (MYB93) and lignin (MYB42) synthesis, genes involved in the synthesis (CYP86B1) and the transport (ABCG20) of suberin monomers and two uncharacterized transcription factors (NAC038 and NAC058) were all upregulated in induced periderm samples. Genes involved in cutin (GPAT6, SHN3) and wax synthesis (KCS10, WSD1, CER6) and transport of cutin monomers and wax components (ABCG11) were all downregulated. Levels of typical suberin monomers (ω-hydroxy-C20, -C22 and -C24 acids) and total suberin were high in the periderms, but low in the cuticle. Periderms were induced only when wounding occurred during early fruit development (32 and 66 days after full bloom (DAFB)) but not later (93 DAFB). Wound and moisture induced periderms are very similar morphologically, histologically, compositionally and molecularly.

Differential Responses of Vanilla Accessions to Root Rot and Colonization by Fusarium oxysporum f. sp. radicis-vanillae.

Root and stem rot (RSR) disease caused by Fusarium oxysporum f. sp. radicis-vanillae (Forv) is the most damaging disease of vanilla (Vanilla planifolia and V. × tahitensis, Orchidaceae). Breeding programs aimed at developing resistant vanilla varieties are hampered by the scarcity of sources of resistance to RSR and insufficient knowledge about the histopathology of Forv. In this work we have (i) identified new genetic resources resistant to RSR including V. planifolia inbreds and vanilla relatives, (ii) thoroughly described the colonization pattern of Forv into selected vanilla accessions, confirming its necrotic non-vascular behavior in roots, and (iii) evidenced the key role played by hypodermis, and particularly lignin deposition onto hypodermal cell walls, for resistance to Forv in two highly resistant vanilla accessions. Two hundred and fifty-four vanilla accessions were evaluated in the field under natural conditions of infection and in controlled conditions using in vitro plants root-dip inoculated by the highly pathogenic isolate Fo072. For the 26 accessions evaluated in both conditions, a high correlation was observed between field evaluation and in vitro assay. The root infection process and plant response of one susceptible and two resistant accessions challenged with Fo072 were studied using wide field and multiphoton microscopy. In susceptible V. planifolia, hyphae penetrated directly into the rhizodermis in the hairy root region then invaded the cortex through the passage cells where it induced plasmolysis, but never reached the vascular region. In the case of the resistant accessions, the penetration was stopped at the hypodermal layer. Anatomical and histochemical observations coupled with spectral analysis of the hypodermis suggested the role of lignin deposition in the resistance to Forv. The thickness of lignin constitutively deposited onto outer cell walls of hypodermis was highly correlated with the level of resistance for 21 accessions tested. The accumulation of p-coumaric and sinapic acids, two phenolic precursors of lignin, was observed in the resistant plants inoculated with Fo072, but not in the susceptible one. Altogether, our analyses enlightened the mechanisms at work in RSR resistant genotypes and should enhance the development of novel breeding strategies aimed at improving the genetic control of RSR of vanilla.

Peperomia leaf cell wall interface between the multiple hypodermis and crystal-containing photosynthetic layer displays unusual pit fields

Leaves of succulent Peperomia obtusifolia (Piperaceae), and its related species, contain a large multilayered hypodermis (epidermis) subtended by a very small single-layered photosynthetic palisade parenchyma, the latter containing spherical aggregates of crystals called druses. Each druse is in a central vacuole surrounded by chloroplasts. All hypodermal cell walls are thin, except for thick lowermost periclinal walls associated with the upper periclinal walls of the subtending palisade cells. These thick walls display 'quilted' impressions (mounds) formed by many subtending palisade cells. Conspicuous depressions occur in most mounds, and each depression contains what appear to be many plasmodesmata. These depressions are opposite similar regions in adjacent thin palisade periclinal walls, and they can be considered special pit fields that represent thin translucent regions ('windows' or 'skylights'). Druses in the vacuoles of palisade cells occur below these pit field regions and are surrounded by conspicuous cytoplasmic chloroplasts with massive grana oriented perpendicular to the crystals, probably providing for an efficient photosynthetic system under low-intensity light. Leaf clearings and fractures, light microscopy and crossed polarizers, general and histochemical staining, and transmission and scanning electron microscopy were used to examine these structures. Druses in the vacuoles of palisade cells occur below the thin pit field regions in the wall interface, suggesting an interesting physical relationship that could provide a pathway for light waves, filtered through the multiple hypodermis. The light waves pass into the palisade cells and are collected and dispersed by the druses to surrounding chloroplasts with large grana. These results imply an intriguing possible efficient photosynthetic adaptation for species growing in low-light environments, and provide an opportunity for future research on how evolution through environmental adaptation aids plants containing crystals associated with photosynthetic tissues to exist under low-light intensity and with other stresses.

Assessment of O2 diffusivity across the barrier to radial O2 loss in adventitious roots of Hordeum marinum.

The subapical regions of wetland plant roots can develop a barrier to radial O2 loss (ROL), but barrier resistance has rarely been quantified in terms of its O2 diffusivity. Barrier resistance in adventitious roots of the waterlogging-tolerant Hordeum marinum was assessed from measurements of ROL using cylindrical platinum electrodes while either varying shoot O2 partial pressures or cooling the rooting medium. Anatomical features were examined using fluorescence microscopy. When grown in stagnant agar nutrient solution, a barrier to ROL was induced over the basal half of 100-120-mm-long roots. Autofluorescence in hypodermal cell walls indicated that putative suberin deposition was coincident with barrier expression. Root cooling revealed a significant respiratory component in barrier resistance. Eliminating the respiration effect by manipulating shoot O2 partial pressures revealed an O2 diffusivity for the barrier of 5.96 x 10(-7) cm2 s(-1), 96% less than that at the apex, which was > or = 1.59 x 10(-5) cm2 s(-1). It is concluded that the ROL barrier is a manifestation of two components acting synergistically: a physical resistance caused principally by secondary cell-wall deposits in the outer hypodermal layer; and respiratory activity in the hypodermal/epidermal layers; with physical resistance being the dominant component.

Effects of NO 3 deficiency and NaCl stress on suberin deposition in rhizo- and hypodermal (RHCW) and endodermal cell walls (ECW) of castor bean (Ricinus communis L.) roots

Castor bean (Ricinus communis L.) plants were hydroponically cultivated to achieve NO3 deficiency (N starvation), salt stress (addition of 100 mM NaCl), or normal conditions. Endodermal (ECW) and rhizodermal and hypodermal cell walls (RHCW) were isolated enzymatically from roots, and suberin monomers were released by transesterification after solvent extraction. Aromatic and aliphatic suberin monomers were identified and quantified by gas chromatography and mass spectrometry. Between 90 and 95% of the released suberin monomers were linear, long-chain, aliphatic compounds (alcohols, acids, diacids, ω-hydroxy acids and 2-hydroxy acids) with an average chain length of 19 C-atoms. The remainder was an aromatic suberin fraction mainly composed of coumaric and ferulic acid. Suberin amounts were significantly increased in ECW and RHCW in the presence of NaCl. In contrast, N starvation led to significantly reduced levels of suberization in ECW and RHCW. It is concluded that R. communis plants reinforce their apoplastic transport barriers in roots in adaptation to NaCl stress in order to minimize NaCl uptake. Under conditions of N starvation the opposite occurs and plants reduce the suberization of their apoplastic transport barriers to facilitate nutrient uptake form the soil.

Biochemical characterization of elongase activity in corn ( Zea mays L.) roots

Chemical analysis of 4-day-old corn ( Zea mays L.) root cell walls revealed that the lipophilic biopolymer suberin forms an important constituent of rhizodermal and hypodermal cell walls. Identified aliphatic monomers had chain lengths ranging from C 16 to C 26 and they belonged to 5 substance classes (ω-hydroxycarboxylic acids, 1,ω-dicarboxylic acids, 2-hydroxycarboxylic acids, carboxylic acids and alcohols) by which suberin is characterized. Biochemical experiments proved the occurrence of elongase activities in corn roots. Highest enzymatic activities were found in corn root microsomes, and major products synthesized by root elongases were elongated fatty acids with chain lengths ranging from C 20 to C 24. Preferred substrates of root elongases were acyl-CoAs of the chain length C 18 and C 20, whereas monounsaturated acyl-CoAs (C 16:1 and C 18:1) and acyl-CoAs of lower (C 12–C 16) and higher chain lengths (C 22–C 24) were rarely elongated. Elongase activities significantly decreased over the length (40 cm) of 10-day-old corn roots going from the young tip to the older base of the root. Thus, results presented here show the presence and activity of elongases in roots of plants.

Apoplasmic barriers and oxygen transport properties of hypodermal cell walls in roots from four amazonian tree species.

The formation of suberized and lignified barriers in the exodermis is suggested to be part of a suite of adaptations to flooded or waterlogged conditions, adjusting transport of solutes and gases in and out of roots. In this study, the composition of apoplasmic barriers in hypodermal cell walls and oxygen profiles in roots and the surrounding medium of four Amazon tree species that are subjected to long-term flooding at their habitat was analyzed. In hypodermal cell walls of the deciduous tree Crateva benthami, suberization is very weak and dominated by monoacids, 2-hydroxy acids, and omega-hydroxycarboxylic acids. This species does not show any morphological adaptations to flooding and overcomes the aquatic period in a dormant state. Hypodermal cells of Tabernaemontana juruana, a tree which is able to maintain its leaf system during the aquatic phase, are characterized by extensively suberized walls, incrusted mainly by the unsaturated C(18) omega-hydroxycarboxylic acid and the alpha,omega-dicarboxylic acid analogon, known as typical suberin markers. Two other evergreen species, Laetia corymbulosa and Salix martiana, contained 3- to 4-fold less aliphatic suberin in the exodermis, but more than 85% of the aromatic moiety of suberin are composed of para-hydroxybenzoic acid, suggesting a function of suberin in pathogen defense. No major differences in the lignin content among the species were observed. Determination of oxygen distribution in the roots and rhizosphere of the four species revealed that radial loss of oxygen can be effectively restricted by the formation of suberized barriers but not by lignification of exodermal cell walls.

Apoplastic barriers in roots: chemical composition of endodermal and hypodermal cell walls

Based on the characterization of the chemical composition of endodermal and hypodermal cell walls isolated from seven monocotyledonous and three dicotyledonous plant species, a model of the composition of apoplastic barriers in roots is proposed. Depending on the species, endodermal and hypodermal cell walls of roots contained varying amounts of the biopolymers suberin, lignin, cell wall proteins, and carbohydrates. Although analysis of the chemical composition of these apoplastic barriers of roots is now possible, it is pointed out that conclusions from these data concerning the functional properties of these cell walls can not easily be drawn. However, in analogy to suberized periderms it is argued that the suberin should play a role in establishing an apoplastic transport barrier in roots, albeit not a perfect barrier. Furthermore, due to the combined occurrence of suberin, lignin and cell wall proteins it is argued that endodermal and hypodermal cell walls also have an important function as barriers towards pathogens. Finally, it is pointed out that additional experimental approaches combining the investigation of transport properties and of the chemical composition of apoplastic transport barriers in roots are necessary before the function of endodermal and hypodermal cell walls in roots can be fully understood.

Review article. Apoplastic barriers in roots: chemical composition of endodermal and hypodermal cell walls

Review article. Apoplastic barriers in roots: chemical composition of endodermal and hypodermal cell walls

Structure and chemical composition of endodermal and rhizodermal/hypodermal walls of several species

CWM, isolated cell wall material ECW, isolated endodermal cell walls G, guaiacyl monomer H, p‐hydroxyphenyl monomer HCW, isolated hypodermal cell walls RHCW, isolated rhizodermal and hypodermal cell walls S, syringyl monomer XV, isolated xylem vessels Endodermal cell walls of the three dicotyledoneous species Pisum sativum L., Cicer arietinum L. and Ricinus communis L. were isolated enzymatically and analysed for the occurrence of the biopolymers lignin and suberin. From P. sativum, endodermal cell walls in their primary state of development (Casparian strips) were isolated. Related to the dry weight, these isolates contained equal amounts of suberin (2·5%) and lignin (2·7%). In contrast, the endodermal cell walls of C. arietinum and R. communis, which were nearly exclusively in their secondary state of development, contained significantly higher proportions of suberin (10–20%) and only traces of lignin (1–2%). The results of the chemical analyses were supported by a microscopic investigation of Sudan III‐stained root cross‐sections, showing a Casparian strip restricted to the radial walls of the endodermis of P. sativum and well‐pronounced red suberin lamellae in C. arietinum and R. communis roots. Compared with recently investigated monocotyledoneous species, higher amounts of suberin by one order of magnitude were detected with the secondary state of development of dicotyledoneous species. Furthermore, the carbohydrate and protein contents of primary (Clivia miniata Reg. and Monstera deliciosa Liebm.), secondary (C. arietinum and R. communis) and tertiary endodermal cell walls (Allium cepa L. and Iris germanica L.) were determined. The relative carbohydrate content of secondary endodermal cell walls was low (14–20%) compared with the content of primary (42–50%) and tertiary endodermal cell walls (60%), whereas the protein content of isolated endodermal cell walls was high in primary (13%) and secondary (8%) and low in tertiary endodermal cell walls (0·9–2%). The results presented here indicate that the quantitative chemical composition of primary, secondary, and tertiary endodermal cell walls varies significantly. Finally, cell wall proteins are described as an additional important constituent of endodermal cell walls, with the highest concentrations occurring in primary (Casparian strips) and secondary endodermal cell walls.

Chemical Composition of Hypodermal and Endodermal Cell Walls and Xylem Vessels Isolated from Clivia miniata (Identification of the Biopolymers Lignin and Suberin).

The occurrence of the biopolymers lignin and suberin was investigated with hypodermal (HCW) and endodermal cell walls (ECW) and xylem vessels (XV) isolated from Clivia miniata Reg. roots. Both biopolymers were detected in HCW and ECW, whereas in XV, typical aliphatic suberin monomers were missing and only representative lignin monomers such as guaiacyl (G) and syringyl (S) units could be detected. The absolute amounts of lignin were about one order of magnitude higher compared with suberin in both HCW and ECW. The ratios of the two aromatic lignin units (G/S) decreased from 39 in XV and 10 in HCW to about 1 in ECW, indicating significant differences in lignin structure and function between the three investigated samples. Additionally, compared with the detectable lignin-derived aromatic units G and S, significantly higher amounts of esterified p-coumaric acid-derived aromatic monomers were obtained with HCW, but not with ECW. This is interpreted as a functional adaption of HCW toward pathogen defense at the root/soil interface. The final aim of this study was to provide a thorough chemical characterization of the composition of HCW, ECW, and XV, which in turn will form the basis for a better understanding of the relevant barriers toward the passive, radial, and apoplastic diffusion of solutes from the soil across the root cortex into the root cylinder.

Texture of host cell walls in mycorrhizal leeks

The ultrastructural texture of cell walls as revealed by subtractive and cytochemical techniques in mycorrhizal and non mycorrhizal roots of Allium porrum is described. Three different cell walls types are involved in the mycorrhizal symbiosis: epidermal, hypodermal and cortical cell walls. While the first types are thick, autofluorescent, and rich in encrusting substances, the cortical cell walls are thin, not autofluorescent and without encrustation. Morphological observations show that the fungal penetration causes i) a clearcut break in the fibrillar component of the epidermal and hypodermal walls together with a deposition of an amorphous material, and ii) a pushing of cortical walls around the penetrating branch.

Chemical (NaOH) Peeling as Viewed by Scanning Electron Microscopy: Pimiento Peppers as a Case Study

ABSTRACTScanning electron microscopy (SEM) was used to examine microstructural changes of pimiento peppers (Capsicum annum L. cv. ‘Truhart’) treated with different NaOH (lye) solutions (1,4, and 9%), maintained at 80°C, for various times (1, 2, and 3 min). Photomicrographs indicated that NaOH removes the epicuticular and cuticular waxes, diffuses uniformly into the fruit where it breaks down epidermal and hypodermal cell walls, and solubilizes the middle lamella causing separation of the skin. In severe treatments the lye also dissolves the parenchyma cells of the mesocarp resulting in considerable loss during processing.

Changements cytochimiques et ultrastructuraux des parois cellulaires de la pellicule du raisin, Vitis vinifera, durant la croissance et la maturation de la baie

Cytochemical and ultrastructural analysis of cell wall characteristics was performed in the dermal system of the grape berry (Vitis vinifera L. cv. Pinot noir), using a test for polysaccharides (periodic acid – thiosemicarbazide – silver proteinate, associated with dimethylsulfoxide extraction). Samples were examined at successive stages of fruit development. The main events of the first growth phase, i.e., thickening of hypodermal cell walls and their tangential extension, continued during the second growth phase. At all the stages of grape development, tangentially expanding walls were typical of actively growing plant cell walls, with an ordered texture, new layer deposition, and progressive rotation of microfibrillar subunits (bow-shaped patterns). At maturity, hydration, swelling of the walls, and an increase in the amount of soluble pectic substances were noticed. No redifferentiation of the cell walls occurred. The cuticle, already differentiated into two layers at the first growth phase, was clearly lamellar during the second. At maturity a number of layers, distinguishable by their cytochemical reactivity, were detected. Cuticle thickness increased during "véraison" and was maintained throughout the second growth phase. A considerable increase in the content of epicuticular waxes was noticed during ripening.

Magnesium Deficiency Results in Increased Suberization in Endodermis and Hypodermis of Corn Roots

The composition of the aliphatic components of suberin in the stele and cortex of young corn (Zea mays L.) roots was determined by combined gas-liquid chromatography/mass spectrometry of the LiAlD(4) depolymerization products. omega-Hydroxy acids were shown to be the major class of the aliphatic components of both the hypodermal (35%) and endodermal (28%) polymeric materials with the dominant chain length being C(24) in the former and C(16) in the latter. Nitrobenzene oxidation of the roots generated p-hydroxybenzaldehyde and vanillin with much less syringaldehyde. Electron microscopic examination of the hypodermal and endodermal cell walls from roots of corn plants grown in a Mg(2+) -deficient (0.03 millimolar) nutrient solution showed that these walls were more heavily suberized than the analogous walls of roots from plants grown in normal (2 millimolar) Mg(2+) levels. Analysis of the LiAlD(4) depolymerization products of the suberin polymers from these roots showed that the roots grown in low Mg(2+) had 3.5 times as much aliphatic suberin monomers on a weight basis as the roots from plants grown in nutrient with normal Mg(2+) levels. Roots from plants grown in Mg(2+) -deficient nutrient solution released 3.8 times the amount of aromatic aldehydes upon nitrobenzene oxidation as that released from normal roots. As the degree of Mg(2+) deficiency of the nutrient solution was increased, there was an increase in the aliphatic and aromatic components characteristic of suberin. Thus, both ultrastructural and chemical evidence strongly suggested that Mg(2+) deficiency resulted in increased suberization of the cell walls of both hypodermis and endodermis of Zea mays roots. The roots from Mg(2+) -deficient plants also had a higher amount of peroxidase activity when compared to control roots.

A correlated histochemical and ultrastructural study of the epidermis and hypodermis of onion roots

Cell walls of mature epidermal and hypodermal cells are autofluorescent when viewed under ultraviolet or blue light. This autofluorescence develops in a centripetal direction, beginning in the outer tangential wall of the epidermis and ending in the inner tangential wall of the hypodermis. The intercellular regions between the epidermis and hypodermis and between the hypodermis and the cortex are dense and also become autofluorescent. Although the walls of the hypodermis provide a barrier to the movement of a high molecular weight fluorescent dye, the walls of the epidermis are permeable. Histochemical studies indicate that lipids and polyphenolics are components of the epidermal and hypodermal cell walls. Both layers are resistant to the wall-degrading enzyme Driselase and to concentrated sulphuric acid, whereas the cortex is digested with both treatments. Observations with the transmission electron microscope show that a complex suberin lamella encases each hypodermal cell but is absent from the epidermis. However, the outer tangential wall and radial walls of the epidermal cells are complex in that layers of different densities are present. Some of these layers, as well as the intercellular regions and the radial walls of the hypodermal cells, bind ferric ions when tissue is fixed in ferric chloride-glutaraldehyde indicating the presence of poly-phenolics in these regions. An extracellular layer covering the outer tangential wall of the epidermis stained positively with a number of histochemical tests for polyphenolics.

Observations on the Phi-Thickenings and Casparian Strips in Pelargonium Roots

An ultrastructural examination of hypodermal cell walls failed to demonstrate the presence of casparian strips as has been reported in the literature. Rather, these cells have supportive phi-thickenings which differ significantly from casparian strips. Adjacent phi-thickenings are convex-convex and stratified in transection, with an uneven surface like the rest of the phi-cell's wall. They may be unbranched or branched and in the latter case, especially, they may appear on tangential as well as radial and transverse walls. They are lignified early in development and are associated with microtubules which lie parallel to the long axis of the thickening. Further, the plasmalemma exhibits no special adherence to the thickened wall region. In each of these and other characteristics phi-thickenings contrast sharply with casparian strips.

OBSERVATIONS ON THE PHI‐THICKENINGS AND CASPARIAN STRIPS IN PELARGONIUM ROOTS

An ultrastructural examination of hypodermal cell walls failed to demonstrate the presence of casparian strips as has been reported in the literature. Rather, these cells have supportive phi‐thickenings which differ significantly from casparian strips. Adjacent phi‐thickenings are convex‐convex and stratified in transection, with an uneven surface like the rest of the phi‐cell's wall. They may be unbranched or branched and in the latter case, especially, they may appear on tangential as well as radial and transverse walls. They are lignified early in development and are associated with microtubules which lie parallel to the long axis of the thickening. Further, the plasmalemma exhibits no special adherence to the thickened wall region. In each of these and other characteristics phi‐thickenings contrast sharply with casparian strips.

AN ANATOMICAL STUDY OF COPPER DEFICIENT WHEAT

Summary Copper deficient and normal wheat var. Kenya was grown in the field and in sand culture. An anatomical investigation of the stem was undertaken and the third internode was studied in detail. The thickness of the epidermal cell wall, the width of the epidermal cell, the thickening of the hypodermal cell walls, the width of the hypodermal layer, the area of the epidermis and hypodermis, the area of lignified hypodermis and the area of unlignified hypodermis were measured in populations of controls and copper deficient plants and were then analysed statistically. The characteristics of the vascular bundles could not be analysed due to their great variability. Results showed that copper deficient wheat was considerably less lignified than the controls; that epidermal and hypodermal cell walls were significantly decreased in thickness, but that the area of the hypodermis remained unchanged. A test to determine the rigidity of wheat stems was devised. Copper deficient stems were significantly less rigid than controls. The copper concentration of the deficient plants studied did not appear to differ in the two treatments, but the total copper content of copper sufficient plants is appreciably higher than that of deficient ones.