摘要:

Predicted increase in ultraviolet‐B (UV‐B: 280–320 mn) radiation may have adverse impacts on growth and yield of rice (Oryza sativaL.), as has been found in studies hitherto. However, most of the studies were conducted in growth chambers or greenhouses where the plants are generally more sensitive to UV‐B than in the field, presumably because of the distorted balance between UV‐B and ultraviolet‐A as well as PAR. This study was conducted to address the effects of enhanced UV‐B on growth and yield of rice under a realistic spectral balance in the field. Three cultivars, “Koshihikari”,‘IR 45’and‘IR 74’were pot‐grown and irradiated with enhanced UV‐B for most of the growing season in the field at Tsukuba, Japan (36°01′N, 140°07′E). The UV‐B enhancement simulated ca 38% depletion of stratospheric ozone at Tsukuba. The results showed no UV‐B effects on plant height, numbers of tillers and panicles, dry weight of the plant parts or the grain yield for any of the 3 cultivars. Natural abundance of13C in the flag leaves was not altered by the UV‐B enhancement either. While UV‐absorbing compounds showed no response to the UV‐B enhancement, chlorophyll contents decreased with enhanced UV‐B. However, the decrease of chlorophyll was limited to an early growth stage with no effect later. We thus found no extraordinary impact of the nearly doubled UV‐B radiation on rice in the field, and it would appear that a reliable prediction of the effects of UV‐B will require experiments carried out over a number of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00175.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Root‐differentiated tissue cultures (PS‐R) fromPisum sativum(cv. Greenfeast) were exposed to a 5 mMsolution of the free radical‐generating compound 2,2′‐azobis (2‐amidinopropane) dihydrochloride (AAPH). The levels of mRNA transcripts for two genes were examined:chs2, encoding a chalcone synthase isozyme, andcab, encoding the chlorophylla/b‐binding protein of the light‐harvesting antenna complex. In light‐grown PS‐R, cab mRNA transcript levels decreased to 14% of controls after 6 h of exposure, whereaschs2mRNA levels increased 50‐fold. In dark‐grown PS‐R,chs2mRNA transcripts increased by 40‐fold compared with the controls. Glutathione determination in light‐grown PS‐R showed no substantial difference in total glutathione (GSHtot), whereas oxidized glutathione (GSSG) increased by 66% after 12 h of exposure. However, in dark‐grown PS‐R a decrease in both GSHtotand GSSG after 6 h was followed by an increase of about 70%, as compared with the controls, after 12 h of exposure. In conclusion, AAPH generated oxidative stress, reflected in changed glutathione levels and induced expression of thechs2gene of the flavonoid biosynthetic pathway and also caused a decreased level of

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00176.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Important functions of water relations are considered to be related to genome size diversity in gymnosperms. We investigated relationships among genome size, dimensional characteristics of conductive cells, and water relations parameters by using young seedlings of sixPinusspecies. Xylem hydraulic conductivity was not correlated with genome size and dimensional characteristics of conductive cells, but the water potential at the turgor loss point was.Pinusspecies with large genome sizes had thick cell walls and small ratios of lumen radii to cell wall thickness in their conductive cells, and those species lost their turgor to tissue dehydration al low water potentials. The characteristics observed in the present study may contribute to pine drought tolerance.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00177.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

To clarify the mechanism of aluminum (Al) toxicity and Al tolerance, we isolated a new clone (pAL201) from a tobacco cDNA library. Northern blot hybridization analysis indicated that the expression of pAL201 is induced by Al treatment and phosphate (P1) starvation. The complete cDNA sequence suggested that this clone encodes a moderately anionic peroxidase (EC 1.11.1.7). Analysis by isoelectric focussing indicated that a moderately anionic peroxidase (approximately pI 6.7) and two cationic peroxidases (pI 9.2 and 9.7) in the soluble fraction are activated by Al treatment and P1starvation, while two moderately anionic isozymes are repressed by these stresses. We suppose that Al ion stress can control the activity of some peroxidase isozymes, one of which is probably induced by enhanced gene expression of pAL201. There is a possibility that some of these isozymes have some functions in Al ion stress.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00178.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The specific activities of aminating NADH‐ and deaminating NAD+‐glutamate dehydrogenase (GDH, EC 1.4.1.2) varied considerably in crude extracts of grapevine (Vitis viniferaL. cv. Sultanina) callus and were dependent on the nitrogen source of the culture medium. However, dialysis of the enzyme preparations resulted in a significant decrease in the deaminating GDH specific activity while the aminating activity was not affected. The presence of malate in the crude extract resulted in erroneous overestimation of the NAD+‐GDH activity through the malate dehydrogenase reaction. Thus, in dialysed extracts, the ratio of the NADH‐GDH/NAD+‐GDH specific activities remained relatively constant irrespective of the nitrogen source. In view of this evidence, we now have modified methods for staining both the NADH‐GDH and NAD+‐GDH activities on gels in order to compare the aminating and deaminating activities of each of the 7 GDH isoenzymes. The results from the staining of NADH‐GDH and NAD+‐GDH activity of enzyme preparations from calluses revealed the same isoenzyme profile. Furthermore, separated leaf isoenzymes showed similar activity ratios and kinetic properties. These results may suggest that each one of the 7 isoenzymes have similar in vitro anabolic and cat

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00179.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Sunflower (Helianthus annuusL.) seedlings were grown in aeroponic chambers which allowed for easy access to and easy harvesting of undamaged roots. In different portions of these roots we followed the rate of ethylene production, levels of 1‐aminocyclopropane‐1‐carboxylic acid (ACC), N‐malonyl‐ACC and ACC oxidase mRNA and activity of ACC oxidase. ACC oxidase was measured with an in vitro assay, ACC and N‐malonyl‐ACC by selected ion monitoring gas chromatography‐mass spectrometry. Ethylene production was highest in the tip of the root and tower in the middle and basal (part nearest the hypocotyl) portions of the root. The levels of ACC and ACC oxidase mRNA mirrored the levels of ethylene production. The lowest quantities of N‐malonyl‐ACC were found in the root tips. Upon gentle transfer of seedlings from an aeroponic system to treatment tubes, ACC content transiently increased; the greatest increase occurred in the tips. This brief rise in ACC content was not correlated with an increase in ethylene production. ACC oxidase activity was lowest in the tip and higher in the middle and base; the opposite of the pattern of ethylene production. Treating the seedlings with ACC produced a rapid rise in ACC content and ethylene production and inhibited root elongation. ACC oxidase activity was not induc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00180.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Xyloglucan endotransglycosylase (XET) activity was measured in apple (Malus domesticaBorkh. cv. Braeburn) pericarp and kiwifruit (Actinidia deliciosa[A. Chev.] C. F. Liang et A. R. Ferguson var.deliciosacv. Hayward) outer pericarp and core tissues in order to establish whether a correlation exists between the activity of the enzyme and different stages of fruit development Whereas the growth rate of kiwifruit paralleled changes in XET activity throughout fruit growth, that of apple did not. Both fruits showed the highest XET activity, on a fresh weight basis, in the first two weeks after anthesis when cell division was at its highest. XET activity then decreased sharply, but as the fruit increased in size (4–8 weeks after anthesis) there was a concomitant increase in XET activity in both fruits. In the latter stage of fruit development (16–26 weeks after anthesis) XET activity increased to peak at harvest in apple fruit. During this time there was relatively little increase in fruit size and presumably therefore minimal cell expansion. XET activity then declined as fruit softened after harvest. In core tissue from kiwifruit, XET activity increased throughout the later stages of fruit growth to harvest maturity in a similar manner to apple, but continued to increase after harvest until fruit were ripe. In contrast, XET activity in the outer pericarp of kiwifruit did not increase until ripening after harvest. In apple tissue up to 30% of the XET activity was cell wall bound and could not be solubilised, even in buffer containing 2MNaCl.The results implicate XET in cell wall assembly during cell division and expansion early in apple and kiwifruit growth. However, the disparity between apple and kiwifruit with respect to XET activity late in fruit development and ripening and the different affinities of the enzyme for the cell wall in each fruit, suggest that XET has several roles in plant development, not all of which are related to cell wall loosening during periods of accelerated gro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00181.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Chlorophyll formation capacity along the seedling of bean (Phaseolus vulgarisL. cv. Brede zonder draad) was investigated. After 7 days of irradiation a gradient was formed, where the primary leaf contained ca 300 times more chlorophyll per gram fresh weight than the lower hypocotyl section and ca 20 times more than the epicotyl. Similar chlorophyll gradients but at lower levels were seen when the seedlings were first placed in darkness for 7 days and then irradiated for 1, 2 or 7 days. Ultrastructural investigation of seedlings grown for 7 days in darkness and then irradiated for 24 h revealed a more developed inner membrane system with grana stacks in plastids of cells in the uppermost hypocotyl section compared to plastids of cells in lower hypocoty] sections. The higher up on the seedling the more the ratio increased of protochlorophyll(ide) emitting at 657 nm to short‐wavelength protochlorophyll(ide). After flash irradiation of the different sections, fluorescence emission spectra with maxima at 680 and 690 nm, respectively, were observed, indicating the formation of short‐ and long wavelength chlorophyll(ide) forms. The lower the ratio of protochlorophyll(ide) emitting at 657 nm to the short‐wavelength protochlorophyll(ide), the less long‐wavelength chlorophyll(ide) was formed after irradiation. However, after continuous irradiation long‐wavelength chlorophyll(ide) was formed. In dark grown roots, where only short‐wavelength protochlorophyll forms were present, it was not possible to transform protochlorophyll to chlorophyll by flash irradiation. Possible explanations for this phenomenon ar

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00182.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Sinapis albaL. was induced to flower by either a long day or a displaced short day. Following collection of leaf (phloem) and root (xylem) exudates from induced and non‐induced plants, polyamines in the exudates were extracted, separated and analyzed quantitatively. The titers of free and conjugated putrescine the major polyamine fractions in all samples, increased early and markedly in leaf exudates during the floral transition, coinciding closely with movement of the floral stimulus out of the induced leaf. By contrast, putrescine titer in the root exudate did not increase. A spray of difluoromethylornithine (DFMO), an irreversible inhibitor of the putrescine‐biosynthetic enzyme ornithine decarboxylase, at hour 8 of the long day considerably reduced the titer of free and conjugated putrescine in leaf exudates, and at the same time, markedly decreased the flowering response of induced plants. This effect of DFMO on flowering was substantially reversed by a simultaneous application of putrescine to the roots. DFMO sprayed on induced plants also suppressed early activation of indices of both mitosis and DNA synthesis in the shoot apical meristem. These results support the view that the extra putrescine synthesized in induced leaves is a necessary component of the floral stimulus in Sina

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00183.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Asparagine synthetase (EC 6.3.5.4) activity was increased 4‐ and 8‐fold when maize (Zea maysL.) seedlings were kept in darkness for 24 h and 7 days, respectively; this increase was abolished by cycloheximide. Irradiation of the dark adapted seedlings with a pulse of red light resulted in a 4‐fold decrease of the enzyme activity within 48 h, which was raised again following a far‐red light pulse. Co‐action of light and benzyladenine, reported for the light‐inducible enzymes, was proved to hold also for the light‐repressible asparagine synthetase. The induction of asparagine synthetase activity in the dark is abolished by glucose, suggesting the possible involvement of the enzyme in the contrae of metabolic fluxes of –carbon and nitrogen through assimi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1996.tb00184.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY