摘要:

Respiration in plants is often divided into growth and maintenance components. From the growth respiration it is possible to estimate the efficiency of conversion of substrate to plant material. Analysis of recent experimental data on this basis suggests that the conversion efficiency is considerably lower in roots than in shoots, which conflicts with biochemical analysis. The conventional method for describing respiration data is developed to incorporate root activity and is applied to a set of experimental data. The model provides a means for estimating the respiratory cost of nitrate uptake and also a possible explanation for the inconsistency between experimental observations and theoretical analysis.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04158.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A comparison was made between the oxygen uptake of roots and leaves and of mitochondria isolated from the same tissues. Ten species were included in this study: three legumes, one C3‐monocotyledon, one C4‐monocotyledon, the rest non‐leguminous C3‐dicotyledons. Root and leaf respiration in all species examined displayed substantial resistance to KCN (0.1–1.0 mM) and the cyanide‐resistant respiration was completely inhibited by salicylhydroxamic acid (SHAM; 10–20 mM). SHAM alone inhibited oxygen uptake to varying degrees, depending on the species. Mitochondria were isolated from roots and leaves of many of the species examined and also displayed cyanide‐resistant oxygen uptake, which was sensitive to both SHAM and tetraethylthiuram disulfide (disulfiram). Concentrations of SHAM greater than 2 mM caused inhibition of the cytochrome path as well as of the alternative path in isolated mitochondria. Respiration rates of intact roots and leaves in the presence of varying concentrations of SHAM alone were plotted against those obtained in the presence of both SHAM and KCN. This plot showed that in vivo the cytochrome pathway was not affected by 10 or 20 mM SHAM in the external solution. We conclude that the activity of the alternative pathway in intact roots and leaves can be reliably estimated by comparing SHAM‐sensitivity and cyanide‐resist

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04159.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The respiration of roots and isolated root mitochondria was investigated inPhaseolus vulgarisL.,Spinacea oleraceaL.;Triticum aestivumL., andZea maysL. Although the respiration of both intact roots and isolated mitochondria displayed resistance to cyanide and sensitivity to SHAM, the percentage resistance and inhibition in roots was not the same as that in the mitochondria, with the exception of wheat. Adding FCCP to roots stimulated oxygen uptake and equalized the effects of SHAM and cyanide on roots and mitochondria. In spinach and maize roots, FCCP stimulated both the cytochrome and alternative pathways, while in bean roots, only the alternative pathway was stimulated. FCCP had little effect on wheat root respiration rates. Potential in vivo rates of oxygen uptake were estimated by expressing rates obtained with isolated mitochondria on a fumarase activity basis, and fumarase activity on a root weight basis. In wheat roots the potential rate was approximately equal to the measured in vivo rate; in the other species the potential rates were substantially greater than measured rates, but approximately equal to uncoupled in vivo rates. Key glycolytic intermediates in roots were measured, and it was found that the phosphofructokinase and pyruvate kinase reactions were displaced far from equilibrium, the degree of displacement being approximately equal in roots with little, and roots with substantial, alternative path engagement. Thus, although glycolysis is controlled, the regulation of this pathway appears to be quite flexible. The results are discussed in terms of possible regulatory mechanisms.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04160.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The interaction of CO2enrichment and drought on water status and growth of pea plants was investigated.Pisum sativumL. (cv. Alaska) plants were grown from seeds in growth chambers using 350 and 675 μl I1 CO2, a photon flux density of 600 μmol M‐2 S‐1, a 16 h photoperiod and a temperature regime of 20/14°C. The drought treatment was started at the beginning of branch initiation and lasted for 9 or 11 days. The water status of the plants was monitored daily by measuring total leaf water potential and stomatal conductance. The total leaf water potential of well‐watered plants was not affected by the CO2level. Under draughting conditions total leaf water potential decreased, with a slower decrease under the high CO2regime, due, at least in part, to reduced stomatal conductance. Upon rewatering, total leaf water potential and stomatal conductance recovered within one day. High CO2counteracted the reduction in height and, to some extent, leaf area that developed in low CO2unwatered plants. Additional CO2had no effect on branch number and did not prevent the complete inhibition of branch development that resulted from drought stress. Removing the drought conditions resulted in a rapid recovery of the internal water status and also a rapid recovery of most, but not all, plant growth pa

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04161.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Vigna cutjangEndl. cv. Pusa Barsati seedlings, subjected to increasing degrees of water stress (−0.5, −1.0, −1,5 MPa), produced an approximately proportional increase in glycolate oxidase activity, hydrogen peroxide (H2O2) and proline content but a decrease in catalase activity, ascorbic acid and protein content. Leaf water potential (leaf ψ) and relative water content (RWC) were also lowered with increasing stress. Pretreatment withl‐cysteine and reduced glutathione (10‐3 M) decreased glycolate oxidase activity, H2O2content, ascorbic acid oxidase activity, proline content and also slightly improved the water status of leaves stressed (−1.0 MPa) for 2 days. Pretreatment of non‐stressed seedlings with these antioxidants had little or no effect. These studies indicate that treatment with antioxidants makes the plant tolerant against water stress by modulating the endogenous levels of H2O2and ascorbic acid in s

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04162.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Sulfate and nitrate uptake capacity, ATP sulfurylase (ATPS) and nitrate reductase (NR) activity were determined in a set of maize hybrids representative of selection cycles carried out during the period 1930 through 1975. All the above metabolic parameters together with the grain yield were improved by the selection. The annual rate of the improvement was higher (double) for sulfate uptake than for ATPS and similar for NR and nitrate uptake. Significant correlations were evidenced between the uptake efficiency of the roots and the enzyme activity in the leaves both for sulfate and nitrate pathways, and also between the uptake and enzyme steps of nitrate and those of sulfate. This offered good evidence of a coupled genetic regulation between nitrogen and sulfur metabolism in maize.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04163.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abscisic acid inhibits light‐induced betacyanin synthesis inAmaranthus caudatusseedlings. Kinetin antagonizes ABA action and restores betacyanin synthesis. Similarly, phenolic compounds also antagonize ABA action and restore the synthesis of betacyanin. When present together phenolic compounds have an additive effect with kinetin in restoring ABA‐inhibited betacyanin synthe

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04164.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Levels of abscisic acid (ABA) and several indicators of leaf‐water status were measured in excised and intact primary leaves of bean (Phaseolus vulgariscv. Kinghorn) exposed to different temperature and moisture regimes. After 2 h at 5°, 25° or 45°C under moist conditions, the water status of detached leaves showed only minor changes, and there was no increase in ABA. Under conditions favoring water loss, ABA rose over 10‐fold at 25°C, and trends towards higher ABA levels were observed at 5° and 45°C. When intact leaves on whole plants were exposed to the same temperatures for 10 h, there was still no evidence of a temperature‐dependent rise in ABA that was not associated with a disturbance in the water balance of the plant. These data suggest that the rapid accumulation of ABA during temperature stress is a function of induced moisture deficits and does not result from high or low temperat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04165.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Diurnal variations of nitrate reductase (NR) activity and stability have been studied in leaves of barley seedlings (Hordeum vulgareL. cv. Herta) grown in an 8 h light/16 h darkness regime. Stability (decay) of NR was tested both in the extracts and in the plants. In the morning, when the plants were transferred to light, NR activity increased rapidly during the first hour and then remained constant. After the photoperiod, activity decreased rapidly during the first hour of darkness and then remained fairly constant during the rest of the dark period. The high NR activity during the photoperiod was associated with low NR stability both in the extracts and in the plants. On the other hand the low NR activity during the dark period was associated with high stability in the extracts and in the plants.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04166.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Leaves of chickpea (Cicer urietinumL.) secrete malic acid hut the significance of this secretion is not known. Our studies have confirmed that secretion of malic acid was mostly confined to the day time. PEP carboxylase activity and the secretion of malic acid are associated with the presence of glands on the surface of leaves and fruit wall. PEP carboxylase activity increased while malic acid secretion and MDH activity decreased in water stressed plants. The secretion of malic acid did not influence the reflectance properties of the crop canopy thereby discounting the possibility of reducing radiation load. It is suggested that the significance of malic acid secretion in chickpea should be considered in relation to insect pests which are very few on this plant.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1983.tb04167.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY