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51.
The morphological and functional organization of the needles of Scotch pine (Pinus sylvestris L.) and Siberian fir (Abies sibirica Ledeb.), which differ in their light requirement were studied. The characteristic properties of the high-light-requiring pine included high rates of apparent photosynthesis and dark respiration, high assimilation number, numerous folds in mesophyll cell walls, and increased partial volume of intercellular spaces and hyaloplasm in the mesophyll. In the needles of shade-enduring fir, the higher efficiency of photosynthesis at low light intensities depended on the higher number of membranes and higher pigment content in the chloroplasts. The low assimilation number in fir indicated a shortage of photosynthetic reaction centers. The relative volume of the vascular cylinder and the vascular bundles in the needles and the partial volume of chloroplasts in the hyaloplasm, are considered as indices of the rate of assimilate export from mesophyll cells and their possible damping at different levels of structural organization. 相似文献
52.
53.
Estelle Villemont Frédéric Dubois Rajbir S. Sangwan Gérard Vasseur Yvan Bourgeois Brigitte S. Sangwan-Norreel 《Planta》1997,201(2):160-172
Chimeric -glucuronidase (GUS) gene expression in an efficientAgrobacterium-mediated transformation system utilising mesophyll cells ofPetunia hybrida synchronized with cell cycle phase-specific inhibitors (mimosine and colchicine) was used to show the absolute requirement of S-phase for transfer and/or integration of the transferred DNA (T-DNA). Flow-cytometric analysis of nuclear DNA content and immunohistological detection of bromodeoxyuridine (BrdUrd) incorporation showed that, prior to phytohormone treatment, most (98%) mesophyll cells were at GO-Gl-phase (quiescent phase) and no cell division was occurring. After 48 h and 72 h of phytohormone treatment, there was a rapid increase in S-G2-M-phase populations (> 75%) and a concomitant decrease (down to 24%) in G0–-G1-phase cells. Assays of GUS showed that maximum transformation (> 95% of explants) also occurred after this period. Our data showed that mimosine and colchicine blocked the mesophyll cells at late Gl-phase and M-phase, respectively. No transformation (= GUS expression) was observed in phytohormone-treated cells inhibited in late G1 by mimosine. However, after removal of mimosine, 82% of the explants were transformed, indicating the non-toxic and reversible effect of the inhibitor. On the other hand, a relatively high transformation frequency (65% of explants) was observed after blocking the cell cycle at M-phase with colchicine. However, only transient, but no stable, gene expression (= kanamycin-resistant callus formation) was observed in colchicine-treated M-phase-arrested cells. Similarly, endoreduplication of nuclear DNA, which occurred during the 48 h of phytohormone treatment in some mesophyll cells and cells located along the minor veins in the leaf explants, resulted in transient GUS expression only. These observations indicate a direct correlation between endoreduplication and transient GUS gene expression. Obviously, for stable GUS gene expression, cell division and proliferation are required, indicating that both DNA duplication (S-phase) and cell division (M-phase) are strongly related to stable transformation. We propose that the present system should facilitate further dissection of the process of T-DNA integration in the host genome and therefore should aid in developing new strategies for transformation of recalcitrant plants.Abbreviations BAP
6-benzylaminopurine
- BM
basal medium
- BrdUrd
bromodeoxyuridine
- GUS
-glucuronidase
- KmR
kanamycin resistant
- T-DNA
transferred DNA 相似文献
54.
Summary Microscopy techniques were used to identify the pathway of transport of soybean leaf vegetative storage proteins (VSP/ and VSP94) to the vacuoles of a specialized cell type, the paraveinal mesophyll (PVM), where they accumulate. PVM cells are enriched in endoplasmic reticulum and Golgi bodies relative to surrounding mesophyll cells. The margins of medial and trans Golgi cisternae had attached or closely associated noncoated vesicles with densely staining membranes and lumenal contents of the same appearance as material that accumulated in the vacuole. These vesicles appeared to be transported preferentially to the tonoplast, where fusion with the membrane released the granular contents into the vacuole. Cytochemical staining with phosphotungstic acid and silver methenamine supported this interpretation as both the Golgi vesicles and the tonoplast stained intensely with these reagents, unlike the tonoplast of mesophyll cells which do not accumulate VSP. Immunocytochemical localization for VSP/ labeled the Golgi bodies and associated vesicles, and vacuolar material in PVM cells, but not in mesophyll. Similar labeling was seen in PVM of another legume species previously found to accumulate antigenically similar VSPs. Immunolocalization for VSP94, a lipoxygenase, labeled the PVM cytosol and material in the PVM vacuole, but not the Golgi or vesicles. The results of this study demonstrate that the Golgi pathway is utilized for transport of VSP/ in the PVM, which follows the mechanism of deposition demonstrated for certain seed storage proteins. VSP94 appeared to follow a separate path for accumulation in PVM vacuoles.Abbreviations LOX
lipoxygenase
- PVM
paraveinal mesophyll
- RER
rough endoplasmic reticulum
- TEM
transmission electron 相似文献
55.
High spatial resolution mass spectrometry imaging reveals the genetically programmed,developmental modification of the distribution of thylakoid membrane lipids among individual cells of maize leaf 下载免费PDF全文
Maria Emilia Dueñas Adam T. Klein Liza E. Alexander Marna D. Yandeau‐Nelson Basil J. Nikolau Young Jin Lee 《The Plant journal : for cell and molecular biology》2017,89(4):825-838
Metabolism in plants is compartmentalized among different tissues, cells and subcellular organelles. Mass spectrometry imaging (MSI) with matrix‐assisted laser desorption ionization (MALDI) has recently advanced to allow for the visualization of metabolites at single‐cell resolution. Here we applied 5‐ and 10 μm high spatial resolution MALDI‐MSI to the asymmetric Kranz anatomy of Zea mays (maize) leaves to study the differential localization of two major anionic lipids in thylakoid membranes, sulfoquinovosyldiacylglycerols (SQDG) and phosphatidylglycerols (PG). The quantification and localization of SQDG and PG molecular species, among mesophyll (M) and bundle sheath (BS) cells, are compared across the leaf developmental gradient from four maize genotypes (the inbreds B73 and Mo17, and the reciprocal hybrids B73 × Mo17 and Mo17 × B73). SQDG species are uniformly distributed in both photosynthetic cell types, regardless of leaf development or genotype; however, PG shows photosynthetic cell‐specific differential localization depending on the genotype and the fatty acyl chain constituent. Overall, 16:1‐containing PGs primarily contribute to the thylakoid membranes of M cells, whereas BS chloroplasts are mostly composed of 16:0‐containing PGs. Furthermore, PG 32:0 shows genotype‐specific differences in cellular distribution, with preferential localization in BS cells for B73, but more uniform distribution between BS and M cells in Mo17. Maternal inheritance is exhibited within the hybrids, such that the localization of PG 32:0 in B73 × Mo17 is similar to the distribution in the B73 parental inbred, whereas that of Mo17 × B73 resembles the Mo17 parent. This study demonstrates the power of MALDI‐MSI to reveal unprecedented insights on metabolic outcomes in multicellular organisms at single‐cell resolution. 相似文献
56.
Leaf hydraulic conductance and mesophyll conductance are not closely related within a single species 下载免费PDF全文
Stomata represent one resistor in a series of resistances for carbon and water exchange between the leaf and the atmosphere; the remaining resistors occurring within the leaf, commonly represented as mesophyll conductance to CO2, gm, and leaf hydraulic conductance, kLeaf. Recent studies have proposed that gm and kLeaf may be coordinated across species because of shared pathways. We assessed the correlation between gm and kLeaf within cotton, under growth CO2 partial pressure and irradiance treatments and also with short‐term variation in irradiance and humidity. gm was estimated using two isotopic techniques that allowed partitioning of total gm (Δ13C‐gm) into cell wall plus plasma membrane conductance (Δ18O‐gm) and chloroplast membrane conductance (gcm). A weak correlation was found between Δ13C‐gm and kLeaf only when measured under growth conditions. However, Δ18O‐gm was related to kLeaf under both short‐term environmental variation and growth conditions. Partitioning gm showed that gcm was not affected by short‐term changes in irradiance or correlated with kLeaf, but was strongly reduced at high growth CO2 partial pressure. Thus, simultaneous measurements of gm, kLeaf and gcm suggest independent regulation of carbon and water transport across the chloroplast membrane with limited coordinated regulation across the cell wall and plasma membrane. 相似文献
57.
The role of cytokinins in the development of mesophyll structure was studied in developing pumpkin Cucurbita pepo L. leaves. Leaves were treated with cytokinins at different stages of growth: when they reached 25 or 50% of their final size (S
max), immediately after leaf growth ceased, and during senescence. At the early stages of leaf development, treatment with exogenous benzyladenine accelerated division of mesophyll cells. At the later stages of development, BA treatment activated expansion of growing cells and those, which have just accomplished their growth. The exogenous cytokinin did not affect the senescent leaf cells. The content of endogenous cytokinins changed during mesophyll development. The juvenile leaves (25% of S
max) were characterized by low level of these phytohormones. In the expanding leaves (50% of S
max), the content of phytohormones increased and decreased when leaf growth ceased. In the senescent leaves, the cytokinin content decreased markedly. It was concluded that the response of mesophyll cells to cytokinin depended on the cell growth phase at the moment of hormone action. Furthermore, in the young leaves, lower cytokinin concentrations were required for division of mesophyll cells in vivo than for cell expansion at the final stage of leaf development. 相似文献
58.
Structural and Functional Changes in the Leaves of Plants from Steppe Communities as Affected by Aridization of the Eurasian Climate 总被引:3,自引:0,他引:3
Voronin P. Yu. Ivanova L. A. Ronzhina D. A. Ivanov L. A. Anenkhonov O. A. Black C. C. Gunin P. D. P'yankov V. I. 《Russian Journal of Plant Physiology》2003,50(5):604-611
Morphological and physiological characteristics of leaves from plant species collected in steppe communities in the various climatic zones in Eurasia were compared. The changes in leaf structure correlated with the major climatic factors. The mean thickness of leaves increased with increasing mean temperature of July and decreasing mean precipitation, which corresponded to aridity increase. The increased leaf thickness correlated with an increase in the specific leaf weight. The content of chlorophylls (a + b) in leaves greatly varied with plant habitats, whereas the chlorophyll a/b ratio remained unchanged. The chlorophyll content in leaf tissues had a general tendency to decrease with increasing leaf thickness. The leaf chlorophyll content positively correlated (R
2 = 0.77) with the proportion of chlorenchyma in leaf tissues. It is concluded that steppe plants adapt to climate aridization at the structural level by increasing the proportion of protective heterotrophic components of the leaf without changing the functional activity of photosynthetic tissues. 相似文献
59.
High-frequency field measurements of diurnal carbon isotope discrimination and internal conductance in a semi-arid species, Juniperus monosperma 总被引:1,自引:0,他引:1
CHRISTOPHER P. BICKFORD NATE G. MCDOWELL ERIK B. ERHARDT & DAVID T. HANSON 《Plant, cell & environment》2009,32(7):796-810
We present field observations of carbon isotope discrimination (Δ) and internal conductance of CO2 ( g i ) collected using tunable diode laser spectroscopy (TDL). Δ ranged from 12.0 to 27.4‰ over diurnal periods with daily means from 16.3 ± 0.2‰ during drought to 19.0 ± 0.5‰ during monsoon conditions. We observed a large range in g i , with most estimates between 0.04 and 4.0 µ mol m−2 s−1 Pa−1 . We tested the comprehensive Farquhar, O'Leary and Berry model of Δ (Δcomp ), a simplified form of Δcomp (Δsimple ) and a recently suggested amendment (Δrevised ). Sensitivity analyses demonstrated that varying g i had a substantial effect on Δcomp , resulting in mean differences between observed Δ (Δobs ) and Δcomp ranging from 0.04 to 9.6‰. First-order regressions adequately described the relationship between Δ and the ratio of substomatal to atmospheric CO2 partial pressure ( p i / p a ) on all 3 d, but second-order models better described the relationship in July and August. The three tested models each best predicted Δobs on different days. In June, Δsimple outperformed Δcomp and Δrevised , but incorporating g i and all non-photosynthetic fractionations improved model predictions in July and August. 相似文献
60.
Photoinhibition is caused by an imbalance between the rates of the damage and repair cycle of photosystem II D1 protein in thylakoid membranes. The PSII repair processes include (i) disassembly of damaged PSII-LHCII supercomplexes and PSII core dimers into monomers, (ii) migration of the PSII monomers to the stroma regions of thylakoid membranes, (iii) dephosphorylation of the CP43, D1 and D2 subunits, (iv) degradation of damaged D1 protein, and (v) co-translational insertion of the newly synthesized D1 polypeptide and reassembly of functional PSII complex. Here, we studied the D1 turnover cycle in maize mesophyll and bundle sheath chloroplasts using a protein synthesis inhibitor, lincomycin. In both types of maize chloroplasts, PSII was found as the PSII-LHCII supercomplex, dimer and monomer. The PSII core and the LHCII proteins were phosphorylated in both types of chloroplasts in a light-dependent manner. The rate constants for photoinhibition measured for lincomycin-treated leaves were comparable to those reported for C3 plants, suggesting that the kinetics of the PSII photodamage is similar in C3 and C4 species. During the photoinhibitory treatment the D1 protein was dephosphorylated in both types of chloroplasts but it was rapidly degraded only in the bundle sheath chloroplasts. In mesophyll chloroplasts, PSII monomers accumulated and little degradation of D1 protein was observed. We postulate that the low content of the Deg1 enzyme observed in mesophyll chloroplasts isolated from moderate light grown maize may retard the D1 repair processes in this type of plastids. 相似文献