摘要:

AbstractIn higher plants the phytohormone ABA is involved in processes that are connected to water deficit, like stomatal closure or desiccation tolerance. In bryophytes, also containing ABA in their tissues, physiological functions remained uncertain for a long time. Quite recently, several papers have shown different effects of exogenously applied ABA: stomatal closure inAnthoceros, drought hardening inFunariaand production of the landform inRiccia. In all these cases the relevant conditions (water deficit) enhance the endogenous ABA level significantly. For induced desiccation tolerance, ABA serves as a mediator to induce specific proteins (dehydrins) strongly connected with this tolerance. Therefore, it can be concluded that in bryophytes ABA has the same function as in higher plants. It acts as a mediator in stress conditions.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00344.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00345.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe study aims at correlations between ultrastructure of rhizodermal membranes and ATPase activities of two gramineous C4‐species effected by salinization of the growth medium.Comparative investigations were done with drought‐resistantSorghumand drought‐sensitive, salt tolerantSpartinaplants grown under steady‐state conditions without or with 40 mol m−3NaCl. Both species sustained this treatment and showed marked influences of salt on growth but not on root respiration. Generally, the intramembraneous particle (IMP) frequencies, found on freeze‐fracture replicates of rhizodermal plasmic fracture faces of the plasmalemma (PPF) and tonoplast (TPF), were higher inSorghumthan inSpartina. NaCl leads in both species to an increase of the rhizodermal IMP frequency in the TPF(∼150%) and PPF(∼120%).The activities of T‐ and P‐ATPase were determined for membrane vesicles from crude extracts and from isolated protoplasts of roots, respectively; the results from both preparations were the same. The vanadate‐sensitive tissue ATPase activities increased under salt stress ∼ 5 times inSorghumand ∼ 2 times inSpartinawhilst the nitrate and azide‐sensitive tissue ATPase activities increased ∼ 6 times only inSorghum.The combination of the results from the membrane fine structures with the biochemical tests points out that salt‐effected increases of ATPase activities ofSorghumroots were ∼4 times higher than the increases of IMP frequencies on rhizodermal membranes; inSpartinathis effect is less intense.It is concluded that a salty environment leads to a higher ATPase activity per IMP in both species. The stronger reaction ofSorghumis explainable by the increase in K+/Na+selectivity of the plasma membrane under salt stress. This is not the case forSpartinabecause the roots of this species include salt which subsequently is sequestered

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00346.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSeveral photosynthetic parameters were examined in the different tissue layers of leaves from the recently characterized crassulacean acid metabolism/C4intermediate plant,Peperomia camptotricha(Nishio and Ting, 1987). Light appears to control the development of certain photosynthetic characteristics within the tissue layers, while factors other than light seem to dictate others. Analysis of the chlorophyll content (including P700) and chlorophyll‐proteins indicated that more light harvesting chlorophylls were associated with reaction centers in the tissues that were shaded by overlying tissue. Electron transport activity and chlorophyll‐protein analysis indicated that the ratio of photosystem I to photosystem II in the spongy mesophyll (the abaxial tissue type and hence most shaded) was elevated relative to the overlying chlorophyll‐rich median palisade mesophyll. The elevated photosystem I relative to photosystem II in the spongy mesophyll ofPeperomia camptotrichamay be related to C4metabolism and an increased requirement fo

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00347.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractVariations in hydraulic conductivity (LP) and the underlying anatomical and morphological changes were investigated for main root‐lateral root junctions ofAgave desertiandFerocactus acanthodesunder wet, dry, and rewetted soil conditions. During 21 d of drying, LPand radial conductivity (LR) increased threefold to fivefold at junctions of both species. The increase in LRwas accompanied by the formation of an apoplastic pathway for radial water movement from the surface of the junction to the stele forA. desertiand by the rupture of periderm by emerging primordia of secondary lateral roots forF. acanthodes. During 7 d of rewetting, LRdecreased for junctions ofA. deserti, as apoplastic water movement was not apparent, but LRwas unchanged forF. acanthodes. Axial conductance (Kh) decreased during drying for both species, largely because of embolism related to the degradation of unlignified cell wall areas in tracheary elements at the root junction. The resulting apertures in the cell walls of such elements would admit air bubbles at pressure differences of only 0.12‐0.19 MPa. Rewetting restored Khfor both species, but not completely, due to blockage of xylem elements by tyloses. About 40% of the primary lateral roots of the monocotyledonA. desertiabscised during 21 d of drying. For the dicotyledonF. acanthodes, which can form new conduits in its secondary xylem, only 10% of the primary lateral roots abscised during 21 d of drying, consistent with the much greater frequency of lateral roots that persist during drought in the field compared with the case for the sympatricA. dese

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00348.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SummaryThe arrangement of cortical microtubules, as documented by immunofluorescence and immunogold‐silver enhancement, changes during the growth and maturation of giant internodal cells ofChara corallina, a process taking approximately 45 days. Transverse microtubules are found throughout growth along with a subset of distinctly non‐transverse microtubules. During the second half of the growing period, when relative growth rates are diminishing, these non‐transverse microtubules become more abundant but a few days prior to growth cessation, they are mostly absent. At about the time of growth cessation the microtubules, while retaining their locally parallel alignment, begin to show increasing deviation from the transverse axis. Eventually, a mosaic of locally parallel yet variably oriented fields of microtubules forms. Many days after growth stops, microtubules become shorter and less numerous and lose parallel alignment, leading to the formation of a random MT pa

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00349.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWestern immunoblot analysis of protein extracts prepared from epidermal peels, whole leaves, and mesophyll protoplasts with ubiquitin and PEPCase antibodies indicated ubiquitinated PEPCase bands and degradation products only in crude extracts which have been obtained in the presence of the proteolysis inhibitors leupeptin and hemin. After ammonium sulfate precipitation and further purification, PEPCase forms were stable and not ubiquitinated. It is assumed, that only a certain part of PEPCase is degraded via the ubiquitin‐dependent proteolysi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00350.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe subcellular localization of calcium in cells of symbiotic partners located within leaf cavities ofAzollawas investigated by using chlorotetracycline, ESI and EELS analysis. Loosely membrane‐bound calcium was evidenced by using CTC or EGTA and CTC, in cytoplasmic regions ofAzollahair cells and in cytoplasm of the cyanobiont. Tightly membrane‐bound calcium revealed by CTC, and ESI and EELS analysis, was observed in cyanophycin granules and carboxysomes of the cyanobiont. A third calcium type, revealed by ESI and EELS analysis, was localized at the level of cell walls of simple and branchedAzollahairs, in the envelope of heterocysts, and in the cell walls of the cyanobi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00351.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractGametophytes of the sensitive fern,Onoclea sensibilisgrow as filaments in the dark and in red light and assume planar morphology in blue light. RNA content and the synthesis of different RNA fractions as monitored by [3H]‐uridine incorporation and chromatography on oligo(dT)‐cellulose column, were consistently low in the dark‐grown gametophytes, high in blue light and intermediate in red light. No new mRNAs were detected in the translation products primed by poly(A)+ RNA isolated from gametophytes grown under any conditions. Of the nearly 30 polypeptide bands identified in thein vitroprofile, some increased in intensity in blue light, while most continued to decay in the dark and in red light. An increase in the intensity of the polypeptide bands was detected when dark‐ or red light‐grown gametophytes were returned to blue light. Abundance of mRNA of the gene for the large subunit of maize ribulose‐1,5‐bis‐phosphate carboxylase/oxygenase (rbcL) remained more or less unchanged during growth of gametophytes in blue light but declined to very low or undetectable levels in red light and in the dark. Transfer of gametophytes from the dark or red light to blue light led to the reappearance ofrbcL mRNA. Within the limits of detectability, these observations indicate that light quality or dark condition does not affect the expression of the genome, but modifies its relative transcriptional activity. Overall, the results support the hypothesis that changes in the rate of synthesis or degradation of certain mRNAs are associated with the growth patterns of gametophytes ofO. sensibilisin the differe

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00352.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of submergence of air‐grown rice seedlings (Oryza sativaL. var. Sasanishiki) on coleoptile growth and ultrastructure, extensibility and chemical composition of the cell walls was investigated. The lag‐time between start of submergence and the onset of the enhancement of growth was less than 4 h. The growth response was associated with a drastic thinning of the cell walls and an increase in wall extensibility. At the outer epidermal wall of both air‐grown and submerged coleoptiles electron‐dense (osmiophilic) particles were detected. During submergence, the net accumulation of cellulose and hemicellulose was reduced, but the increase in pectic substances was unaffected. Submergence caused an 80% inhibition of the net accumulation of wall‐bound phenolics (ferulic‐ and diferulic acid) compared with air‐grown controls. The osmotic concentration of the tissue saps was not affected by submergence. Our results support the hypothesis that rapid coleoptile elongation under water is caused by an inhibition of the formation of phenolic cross‐links between matrix polysaccharides via diferulate, which results in a mechanical stiffening of the cell walls in the air

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00353.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY