Abstract: Both the mesophyll and bundle-sheath cells associated with the minor veins in the leaf of Amaranthus retroflexus L. contain abundant tubular endoplasmic reticulum, which is continuous between the two cell types via numerous plasmodesmata in their common walls. In bundle-sheath cells, the tubular endoplasmic reticulum forms an extensive network that permeates the cytoplasm, and is closely associated, if not continuous, with the delimiting membranes of the chloroplasts, mitochondria, and microbodies. Both the number and frequency of plasmodesmata between various cell types decrease markedly from the bundle-sheath - vascular-parenchyma cell interface to the sicve-tube member - companion-cell interface. For plants taken directly from lighted growth chambers, a stronger mannitol solution (1.4 M) was required to plasmolyze the companion cells and sieve-tube members than that (0.6 M) necessary to plasmolyze the mesophyll, bundle-sheath, and vascular-parenchyma cells. Placing plants in the dark for 48 h reduced the solute concentration in all cell types. Judging from the frequency of plasmodesmata between the various cell types of the vascular bundles, and from the solute concentrations of the various cell types, it appears that assimilates are actively accumulated by the sieve-tube - companion-cell complex from the apoplast.

Abstract: The intracellular localization of phosphoenolpyruvate (PEP) carboxylase in plants belonging to the C4, Crassulacean acid metabolism (CAM) and C3 types was invetigated using an immunocytochemical method with an immune serum raised against the sorghum leaf enzyme. The plants studied were sorghum, maize (C4 type), kalanchoe (CAM type), french bean, and spinach (C3 type). In the green leaves of C4 plants, it was shown that the carboxylase was located in the mesophyll and stomatic cells, being largely cytosolic in the mesophyll cells. Similarly, in CAM plants, the enzyme was found mainly outside the chloroplasts. In contrast, in C3 plants, the PEP carboxylase appeared to be distributed between the cytosol and the chloroplasts of foliar parenchyma. Examination of sections from etiolated leaves showed fluorescence emission from etioplasts and cytosol for the parenchyma of french bean as well as for the bundle sheath and mesophyll of sorghum leaves. This data indicated that during the greening process photoregulation and evolution of PEP carboxylase is dependent on the tissue and on the metabolic type of the plant considered.

Abstract: In Zea mays L. (cv. XL 72 A) leaves sulphur deficiency caused reduction of soluble protein and chlorophyll contents, whereas ATP sulphurylase (EC 2.7.7.4) and O-acetylserine sulphydrylase (EC 4.2.95.9) activities increased with the increasing of S-deprivation time. The two enzymes exhibited the maximum activity after 5 d (ATP sulphurylase) and 3 d (O-acetylserine sulphydrylase) from the beginning of deprivation period. The activities were differently distributed between mesophyll protoplasts and bundle sheath strands. The results suggest that the activity of the two enzymes may be induced sequentially and differently regulated in the two types of cells.

Abstract: Two-dimensional electrophoresis was performed on proteins of bundle sheath and mesophyll cells isolated from the C 4 grass Digitaria sanguinalis (L.) Scop. Two-dimensional maps of these proteins were constructed and ribulose-1,5-biphosphate carboxylase and phosphoenolpyruvate carboxylase were identified. Of the total number of proteins found in both cell types, 36% were found only in bundle sheath cells, 17% only in mesophyll cells, and 47% in both cell types. By comparison, the distributions of 48 enzymes assayed in these cell types were 35%, 21%, and 44%, respectively. Protein patterns were also compared with C 4 plants exhibiting different decarboxylation pathways and, in both bundle sheath and mesophyll cells, proteins were found which were unique to each species. Bundle sheath proteins of one C 4 species were found to be more like bundle sheath proteins of another C 4 species than like mesophyll proteins of the same species.

Abstract: Seven ultrastructurally distinct types of chloroplast can be distinguished in the leaves of Amaranthus retroflexus L., each unique to a different cell type: vascular parenchyma, companion, bundle sheath, spongy parenchyma, palisade parenchyma, ordinary epidermal, and guard cells. All chloroplasts contain grana and plastoglobuli, and all may contain starch grains. The chloroplast types differ mainly in the degree of grana development and the nature and degree of development of peripheral membranes. Other differences occurring among chloroplast types include variations in starch and crystal content and in shape and size. The sieve-tube plastids, which lack grana, contain a ring of fibrous material typical of such plastids in the Caryophyllales.

Abstract: In an ultrastructural and cytochemical study of tentoxin-treatedSorghum bicolor (L.) Moench, both bundle sheath and mesophyll plastids were severely affected, Plastids from chlorotic leaf areas lacked most internal membranes yet had plastid ribosomes and large fibrillar areas of plastid DNA. In “recovered areas” (mottled yellow and green), cells were found that had plastids of near-normal ultrastructure as well as the severely affected plastid-types found in chlorotic leaf areas. Polyphenol oxidase (PPO) cytochemistry of these mottled leaf areas indicated that all “recovered” mesophyll plastids had PPO whereas all the abnormal mesophyll plastids showed no activity. Because bundle sheath plastids ofSorghum have no PPO activity at any developmental stage, yet are affected by tentoxin, PPO cannot be uniquely affected by this toxin. We suggest that tentoxin may affect the transport of cytosolic proteins into the plastid.

Abstract: Mesophyll cells and bundle sheath strands isolated from leaves of the C4 plant Digitaria sanguinalis (L.) Scop. are capable of utilizing aspartate as a Hill oxidant. The resulting O2 evolution upon illumination depends on the presence of 2-oxoglutarate, is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and is stimulated by methylamine. The rate of aspartate-dependent O2 evolution with mesophyll cells was similar to those with phosphoenolpyruvate + CO2 or with oxalacetate. Amino-oxyacetate, an inhibitor of aspartate aminotransferase, inhibited the aspartate-dependent O2 evolution. Aspartate aminotransferase and NADP+ -malate dehydrogenase are located in the mesophyll chloroplasts. These data suggest that aspartate is converted to oxalacetate via aspartate aminotransferase in the chloroplasts of mesophyll cells and that oxalacetate is subsequently reduced to malate, which is coupled to the photochemical evolution of O2. This suggestion is further verified by the inhibition of phosphoenolpyruvate-dependent 14CO2 fixation by aspartate + 2-oxoglutarate, which presumably acts as oxalacetate and competes with phosphoenolpyruvate + CO2 for NADPH. dl-Glyceraldehyde inhibited aspartate-dependent O2 evolution in the bundle sheath strands but not in the mesophyll cells. The data indicate that aspartate may be converted to malate in both mesophyll and bundle sheath cells. In NADP+ -malic enzyme species, aspartate may exist as a C4-dicarboxylic acid reservoir which can contribute to the C4 cycle through its conversion to malate.

Abstract: Paradiplosis tumifex induces a simple, single-chambered, prosoplasmic gall on the adaxial surface of current-year needles of balsam fir. Proliferating and enlarged mesophyll cells surround the immature larva except for an ostiolar opening on the adaxial surface. The vascular bundle is not affected by gall formation, but the cells lining the resin ducts are altered. As the gall matures the epidermis and one or two layers of underlying mesophyll cells become lignified. Concentrations of starch granules are retained in gall cells after starch has been dissipated in tissues beyond the gall and in nongalled needles. Host damage occurs when galled needles dry and abscise prematurely.

Abstract: The distribution and molecular weights of cellular proteins in soluble and membrane-associated locations were analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Coomassie blue staining of leaf (Digitaria sanguinalis L. Scop.) extracts and isolated cell extracts. Leaf polypeptides also were pulse-labeled, followed by isolation of the labeled leaf cell types and analysis of the newly synthesized polypeptides in each cell type by electrophoresis and fluorography.Comparison of the electrophoretic patterns of crabgrass whole leaf polypeptides with isolated cell-type polypeptides indicated a difference in protein distribution patterns for the two cell types. The mesophyll cells exhibited a greater allocation of total cellular protein into membrane-associated proteins relative to soluble proteins. In contrast, the bundle sheath cells exhibited a higher percentage of total cellular protein in soluble proteins. Phosphoenolpyruvate carboxylase was the major soluble protein in the mesophyll cell and ribulose bisphosphate carboxylase was the major soluble protein in the bundle sheath cell. The majority of in vivo(35)S-pulse-labeled proteins synthesized by the two crabgrass cell types corresponded in molecular weight to the proteins present in the cell types which were detected by conventional staining techniques. The bundle sheath cell and mesophyll cell fluorograph profiles each had 15 major (35)S-labeled proteins. The major incorporation of (35)S by bundle sheath cells was into products which co-electrophoresed with the large and small subunits of ribulose bisphosphate carboxylase. In contrast, a major (35)S-labeled product in mesophyll cell extracts co-electrophoresed with the subunit of phosphoenolpyruvate carboxylase. Both cell types exhibited equivalent in vivo labeling of a polypeptide with one- and two-dimensional electrophoretic behavior similar to the major apoprotein of the light-harvesting chlorophyll a/b protein. Results from the use of protein synthesis inhibitors during pulse-labeling experiments indicated intercellular differences in both organelle and cytoplasmic protein synthesis. A majority of the (35)S incorporation by crabgrass mesophyll cell 70S ribosomes was associated with a pair of membrane-associated polypeptides of molecular weight 32,000 and 34,500; a comparison of fluorograph and stained gel profiles suggests these products resemble the precursor and mature forms of the maize chloroplast 32,000 dalton protein reported by Grebanier et al. (1978 J. Cell Biol. 28:734-746). In contrast, crabgrass bundle sheath cell organelle translation was directed predominantly into a product which co-electrophoresed with the large subunit of ribulose bisphosphate carboxylase.

Abstract: Petiole development and formation of xylem vessels have been investigated in Xanthium leaves from early ontogeny to maturity. Kinetics of growth was presented in terms of absolute and relative elemental rates of elongation. The process of vascularization was assessed by the number of differentiated xylem vessels. The leaf plastochron index (LPI) developed by Erickson and Michelini (1957) was used for designating the various stages of development. An exponential increase in petiole length was observed between the LPIs -3 and +4 indicating a constant relative rate of 0.20 or 20% increase per day. After cessation of lamina elongation at LPI 8, petiole elongation continued for an additional 5 day period, to LPI 9.5. Relative elemental rate analysis revealed that the basipetal pattern of elongation was maintained throughout the leaf development. At a specific plastochron age, the only growth was due to the petiole elongation. Leaves which ceased elongating had not completed their internal development, since the process of xylem formation continued for several plastochrons, or about 8 days. The highest rate of xylem formation was ten vessels per day at LPI 5. On the average, about five xylem vessels differentiated per day in the middle portion of a Xanthium petiole. Mature petioles contained an average of 218 xylem vessels. About 12 canals of schizogenous origin preceeded the development of the vascular tissue. THE PETIOLE is a leaf organ which connects the lamina with the stem. Although its tissues are comparable to the primary tissues of the stem, a considerable variation exists in the distributon of vascular bundles (Esau, 1964). From the physiological point of view, the transport of inorganic and organic molecules between the blade and the stem appears to be the main function. Frequently the petioles bend and elongate in such a way that the blades become favorably oriented toward light to facilitate energy absorption for photosynthesis. Special situations may arise in which petiole tissue will initiate a new plant by means of a vegetative reproduction. Petioles of isolated primary leaves of young bean plants, under suitable circumstances, form roots without addition of exogenous growth substances (Varga and Humphries, 1974). Relatively little has been written about the development of intact petioles in a normal undisturbed situation. The available information 'Received for publication 15 September 1980; revision accepted 24 November 1980. We are grateful to Dr. A. Sievers from Botanisches Institute der Universitat Bonn and Dr. Ch. Fuchs from Museum National D'Histoire Naturelle, Paris for sending us articles by Hilderbrandt, Van Tieghem and Vuillemin. We also thank Dr. Eugene F. McIntyre from the University of Pennsylvania and Alexandra Maksymowych for reading the manuscript. Special thanks to Dr. Barbara F. Palser from Rutgers University for helpful suggestions concerning the terminology of petiole anatomy. on petiole anatomy is fragmentary. Little attention has been given to ontogenetic and quantitative aspects of the problem. As a result, there is scarcity of data on the rates of xylem formation relative to specific stages of leaf development. Isebrands and Larson (1977) investigated vascular anatomy of cottonwood (Populus deltoides) petioles and the relationship between vascular bundles in the petiole and specific portions of the lamina. They found that acropetally differentiating subsidiary bundles provided a vascular continuity between the stem and specific portions of the leaf lamina. Bundles continuous with the central leaf trace were functionally related to the tip region of the lamina, while subsidiary bundles continuous with the lateral leaf traces were functionally connected to specific veins of the middle and basal parts of the lamina. More recently, Esau and Charvat (1978) studied differentiation of primary xylem vessels in petioles of Phaseolus vulgaris L. This investigation was confined to ultrastructural aspects of differentiation, such as the thickening of the primary wall, development of secondary wall depositions, and perforations in the end walls. Our investigation is limited to two aspects of petiole development, basic growth kinetics and formation of xylem vessels. The relative elemental rates of elongation and rates of xylem formation have been estimated during the

Abstract: Basipetal transport of [5-3H] IAA in the wheat coleoptile 3H-IAA was applied to the tips of intact wheat coleoptiles (Triticum sativum L., var. Capitole) for 30, 60 or 120 min. The quantity of label per segment (1.5 mm), determined by liquid scintillation counting, was a decreasing exponential function of distance from the source of radioactivity. Chromatographic analysis showed that 3H-IAA was transported more rapidly than its tritiated metabolites. Antoradiographs of semi-thin sections were performed after application of 3H-IAA during 2 h and after treatment by DCC [1-(3-dimethyl-aminopropyl)-3-ethycarbodiimide hydrochloride]. The quantity of label per tissue and per cell was determined at 1.5, 3.0 and 4.5 mm from the tip. Tritiated IAA was estimated to account for 70 to 100% of the label, depending on the distance from the tip. The amount of auxin transported basipetally was greatest in the parenchyma, with lesser amounts transported in the inner and outer epidermis. Tissues of the vascular bundles did not contain more than 10% of total radioactivity of the coleoptile sections. The rate of auxin transport was greater in xylem and parenchyma than in epidermis and bundle sheath. Movement was very slow in procambium and phloem. In parenchyma and epidermis the quantity of label per cell as a function of distance from the tip agreed with the model of exponential regression. These results support the theory of polar diffusion of auxin.

Abstract: Cells with secondary wall thickenings are present in the style of Lilium longiflorum Thunb. cv. Arai 5. These cells are located just outside the three vascular bundles radial to the protophloem. The cells are not present everywhere but occur “at random” along the three vascular bundles. They are surrounded by small elongated parenchyma cells. The secondary wall is lignified but their lignification is less than that of the xylem cells. A relationship has been demonstrated between the presence of these cells and the registration of bioelectric potential changes.

Abstract: Seedlings of an inbred line of male-fertile corn possessing the gene rhm for resistance to Southern corn leaf blight were inoculated with conidia of Helminthosporium maydis race O. Histological observations at 1 day revealed that lesions were comprised of several dead mesophyll cells bordered by a pair of vascular bundles. By 4 days, lesions had only spread to a width of three vascular bundles. Ultrastructural observations revealed that although mesophyll cells degenerated at an early stage, bundle sheath and phloem cells remained intact even in 4-day-old lesions. It appears that the gene rhm imparts a resistance to bundle sheath and phloem cells against toxic substances released by the fungus. Addition key words: Zea mays L., ultrastructure, gene rhm, Southern corn leaf blight.

Abstract: Seedlings of a susceptible inbred line of male-fertile corn were inoculated with conidia of Helminthosporium maydis race O. Histological and ultrastructural observations of mesophyll, bundle sheath and phloem were made over a period of 8 days. Histological observations at 1 day revealed that lesions were comprised of several dead mesophyll cells bordered by a pair of vascular bundles. By 3 days lesions had developed their characteristic appearance caused by mesophyll collapse and had increased to a width of 10–12 bundles. At the ultrastructural level, the first signs of mesophyll cell change were rupture of the tonoplast and swelling of the mitochondrial matrix followed by a disintegration of the cytoplasm and swelling of the chloroplast stroma. Following these changes the cytoplasm became filled with an electron dense material and the plasmalemma ruptured leaving only partial remnants of chloroplasts as recognizable organelles. All of these changes occurred by 1 day. Bundle sheath cells were more resistant and intact cells could be observed in 3-day-old lesions. Phloem showed signs of degeneration by 1 day with distortion of the sieve-tube element membranes and disintegration of the companion cell cytoplasm. By 4 days the phloem had disintegrated.

Abstract: The activities of potato nucleotide pyrophosphatase and cyclic nucleotide phosphodiesterase against a common substrate, p-nitrophenyl thymidine 5′-phosphate and its histochemical analogue, AS-BI-naphthyl thymidine 5′-phosphate, were determined with the aid of relatively specific inhibitors, NAD and 2′,3′-cAMP, respectively. These inhibitors were utilized to reexamine wheat (Triticum aestivum L. cv. Mironovska 808) seeds and 3–5-d old shoots for the occurrence and histochemical localization of nucleotide pyrophosphatase, and to establish the localization of cyclic nucleotide phosphodiesterase. Nucleotide pyrophosphatase is a cytoplasmic enzyme found to be particularly active in the coleoptile epidermis and hypodermis, leaf mesophyll, as well as in developing fibres and phloem. Cyclic nucleotide phosphodiesterase is also a cytoplasmic enzyme active in the shoot vascular bundles, particularly the xylem, and in the seed. Within the seed it is highly active in the crushed cell layer adjacent to the scutellum and in endosperm cells adjacent to the aleurone layer. Within the embryo, cyclic nucleotide phosphodiesterase is most active in epithelial cells adjacent to the crushed cell layer, the suspensor, radicle and root-cap, as well as in the pro-vascular tissues of the scutellum.

Abstract: The anatomy of the leaf galls on some Gramineae infected with several Reoviridae and in maize plants showing wallaby ear disease symptoms has been compared by light and electron miccrocopy. The eoviridae-induced galls were observed to be the result of abnormal cell proliferation within the vascular tissue cells which contained virus particles and virus-induced structures. Leaf galls on wallaby ear diseased plants were seen to be the result of hyperplasia of non-vascular cells principally the bundle sheath cells, in which no virus-like particles or virus-related structures were detected.

Abstract: Epidermal tissue system in terminal leaflet of the first trifoliate leaf of soybean plant (cv. Raiden) was observed by clearing method, SUMP method and paraffin method. Four types of cells, i.e. stomata (guard cells), ordinary epidermal cells, setaceous trichomes and clavate trichomes were recognized in the epidermis. There were many stomata on both adaxial and abaxial epidermis covering mesophyll tissue, but few on epidermis above vein in which bundle sheath extention (BSE) developed until epidermis (Fig. 1, 2). Stomatal density (number of stomata per unit leaf area) in abaxial surface was higher than that in adaxial surface (Fig. 9). In both surfaces it was highest at the middle part of the leaf blade near the midvein and low at the leaf top, base and margin (Fig. 9). Setaceous and clavate trichomes were present mainly on both adaxial and abaxial epidermis above veins around which BSE developed and touched with the epidermis, where the basal cells of these trichomes came in contact with the BSE (Fig. 2, 4, 6, 7). The number of both trichomes per unit midvein length in abaxial epidermis was approximately twice that in adaxial epidermis, and in both sides of midvein the number was largest at the middle position of it (Table 1). Many setaceous trichomes were present also at the leaf margin (Fig. 3, 5). When soybean plants were exposed to dark with saturated air humidity, many water drops were identified on both surfaces of leaf blades (Fig. 8) and the distribution of them coincided with that of clavate trichomes. These results suggested an excessive water of leaf be exuded out through the following pathway; xylem→bundle sheath→bundle sheath extention→clavate trichome, where the last trichome acts as a hydathode. It was also suggested that setaceous trichomes too may play a role in water physiology of young leaves.

Abstract: The vascular system of the leaves of Saccharum officinarum L. is composed in part of a system of longitudinal strands that in any given transverse section may be divided into three types of bundle according to size and structure: small, intermediate, and large. Virtually all of the longitudinal strands intergrade, however, from one type bundle to another. For example, virutually all of the strands having large bundle anatomy appear distally in the blade as small bundles, which intergrade into intermediates and then large bundles as they descend the leaf. These large bundles, together with the intermediates that arise midway between them, extend basipetally into the sheath and stem. Most of the remaining longitudinal strands of the blade do not enter the sheath but fuse with other strands above and in the region of the blade joint. Despite the marked decrease in number of bundles at the base of the blade, both the total and mean cross-sectional areas (measured with a digitizer from electron micrographs) of sieve tubes and tracheary elements increase as the bundles continuing into the sheath increase in size. Linear relationships exist between leaf width and total bundle number, and between cross-sectional area of vascular bundles and both total and mean cross-sectional areas of sieve tubes and tracheary elements.