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121.
122.
From 100 g sunflower seeds, 1.2 mg purified -galactosidase was obtained with an overall yield of 51%. The -galactosidase acted on both terminal -galactosyl residues and side-chain -galactosyl residues of the galactomanno-oligosaccharides and galactomannans. The cDNA coding for sunflower -galactosidase was cloned and the deduced amino acid sequence revealed that the mature enzyme consisted of 363 amino acid residues with a molecular weight of 40263. Seven cysteine residues were found but no putative N-glycosylation sites were present in the sequence. The deduced amino acid sequences of mature enzyme and -galactosidases from coffee, guar and Mortierella vinacea -galactosidase II showed over 81%, 77%, and 47% homology, respectively. These enzymes are classified into the third group in which the enzyme has no insertion sequence and a broad specificity on galactomanno-oligosaccharides compared to the other groups. 相似文献
123.
124.
The estimation of soil water reserves is essential for irrigation management. The usual way of calculating these reserves, held between the soil moisture content at field capacity and the classical limit of –1.5 MPa considered as the lower limit of available water, over the rooting depth of the crop, does not correspond with the real behaviour of crops as regards their ability to extract soil water and should be only considered as the apparent available water (AAW). Measurements of moisture profiles made using a neutron probe soil moisture meter from 1970 until 1991 on unirrigated crops at the INRA Agronomy Station at Toulouse-Auzeville, France, on a deep silty clay soil with a high water holding capacity have enabled us to define the water extraction capacities of maize ( Zea mays L.), sunflower (Helianthus annuus L.), sorghum (Sorghum bicolor L. Moench), soya bean (Glycine max L. Merr.), and winter wheat (Triticum aestivum L.). The results show, not only that all the crops can extract soil water from beyond –1.5 MPa in the surface layers to varying degrees and depths, depending on the crop, but also that deeper down, AAW is not fully used, as the moisture profile gradually returns to field capacity. Of the five crops studied, maize extracts the most water from the top 0.5 m, removing 150% of AAW. This amount falls rapidly lower down, reaching nil at 1.6 m. Conversely sunflower extracts less near the surface, but uses all AAW up to 1.2 m, and still extracts 85% of AAW at 1.6 m. Sorghum is somewhat comparable to sunflower, but with a lower use over the entire profile. Soya bean exhibits strong extraction to 1.0 m, and then much less at depth. As to wheat, its extraction capability is quite high near the surface, and then falls steadily with depth where it is still 30% of AAW at 1.6 m. Soil moisture measurements realised on a bare soil during several successive years were used to fix the maximum soil evaporation and to suggest the contribution of crops in soil water depletion from uppermost layers.The water extraction capacities have been modelled and introduced into the model EPICphase, a modified version of the model EPIC, adapted for irrigation management. Four parameters have been introduced to simulate: (1) the rooting pattern of the crop (parameter ), (2) the degree of involvement of deep layers (parameter p), (3) the fraction of AAW beyond which crop transpiration is affected (parameter t) and (4) the intensity of extraction beyond the limit of –1.5 MPa as a function of soil depth (parameter d). Calibrated on the basis of the driest year since 1970 for each crop, the model was then validated under unirrigated conditions, and then tested on irrigated maize plots. Under unirrigated conditions, the simulations correctly reproduced the water extraction by the five crops, both in an extremely dry year and in a wet year. The observed differences between simulations and observations were found mostly at about 0.1 m depth, and were due to lack of precision of moisture measurements with the neutron probe. From 0.2 to 0.6 m the simulations have a tendency to overestimate the extraction. These differences are explained by water fluxes which are especially high in these layers because of the processes of evaporation from the soil and plant transpiration, which are difficult to simulate with precision. Below 0.6 m, a more stable zone where water movements are of minor importance, the simulations are very precise. For irrigated maize, the results show a very good fit between simulation and measurement, indicating that these water extraction capacity figures could be used for irrigation management provided that the rules for exploitation of the water reserves are well established. 相似文献
125.
Transformed tissues can be efficiently selected with the help of selectable markers. We studied the influence of genotype, culture medium, and chemical nature of selectable markers on the callus formation of sunflower ( Helianthus annuus L.) hypocotyl explants during the selection process. Kanamycin was found not to be a suitable marker for sunflower transformation, while paromomycin and phosphinotri-cin are both useful. Because the mechanism of action of these inhibitors is intimately connected with the physiological reactions of the cultured tissues, we investigated the influence of key media components on the efficiency of selection of transformed callus on phosphinotricin. Auxin, cytokinin, and gibberellic acid, as well as nitrate concentration, all had a strong influence on the spontaneous resistance of untrans-formed sunflower hypocotyl explants against this herbicide. The number of transformed cells varied in function of the growth regulator balance. Possible reasons for this media dependence are discussed. 相似文献
126.
127.
A sunflower genotype (Helianthus annuus L. cv. Florom-328) able to regenerate plants from in vitro cultures was identified by screening hybrids and inbred lines. Protoplasts of this genotype were isolated from dark grown hypocotyls and were cultured in droplets of agarose-solidified V-KM medium covered by liquid V-KM supplemented with naphthaleneacetic acid (NAA) and benzylaminopurine (BAP). One week later colonies were subjected to 2,4-dichlorophenoxyaceticacid for a one week period. Further culture in V-KM with reduced concentrations of NAA and BAP resulted in the appearence of somatic embryos. Maturation of embryos was achieved by culture on MS medium supplemented with NAA, BAP, gibberellic acid A3 and the ethylene inhibitor AgNO3. Embryos were then transferred onto hormone free MS medium for germination. The frequency of shoot formation in the best case was 9.6 percent of viable colonies (1.3 percent of protoplasts plated). Some of the shoots with roots could be transplanted into soil, others were grafted on hypocotyls of in vivo germinated seedlings. Eighty percent of grafted shoots and over 95 percent of rooted shoots survived. The plants flowered and produced 5 to 10 seeds each. Factors affecting the frequency of embryo formation and plant regeneration are discussed.Abbreviations BAP
6-benzylaminopurine
- GA3
gibberellic acid
- MES
morpholinoethanesulfonic acid
- MS
Murashige and Skoog medium
- NAA
naphthaleneacetic acid
- V-KM
protoplast culture medium of Binding and Nehls
- 2,4D
2,4-dichlorophenoxyacetic acid 相似文献
128.
D. C. Sandys‐Winsch J. M. Whipps J. S. Fenlon J. M. Lynch 《Biocontrol Science and Technology》1994,4(3):269-277
A multi‐test screening system identified 63 fungal isolates with high in vitro biocontrol activity against Sclerotinia sclerotiorum. A bioassay method was developed, using sunflower seedlings growing in an unsterilized loam mixture. Twenty‐six isolates were tested in a series of five bioassay tests and a significant correlation (P < 0.01) was found between sclerotial infection in vitro and the number of healthy plants in vivo. Conversely, activity in an in vitro mycelial overgrowth test was not significantly correlated with activity in vivo. However, some isolates showing only mycelial activity still exerted significant disease control in both the bioassays at Littlehampton and in three additional bioassays at Sittingbourne. Only one isolate not previously reported showed significant activity in both sets of bioassays and the lack of consistency in disease control activity by all other isolates, and biocontrol agents in general, was deemed a major barrier to their use. 相似文献
129.
Akio Furukawa 《Ecological Research》1992,7(2):147-153
The ontogenetic changes in stomatal size, frequency and conductance (gs) on abaxial and adaxial leaf surfaces of sunflower plants (Helianthus annuus L. Russian Mammoth) were examined under controlled environmental conditions. The stomatal frequency on the adaxial and abaxial
leaf surfaces decreased with leaf ontogeny and insertion level. The ratio of adaxial to abaxial stomatal frequency did not
change with leaf ontogeny and insertion level, and 42–44% of total stomata was apportioned to the adaxial surface. Ontogenetic
changes in stomatal pore length were detected and increased with ontogenesis. The stomatal length of both leaf surfaces had
linear relationships with leaf area. Ontogenetic changes in gs were similar between the two surfaces. However the adaxial gs was lower than abaxial gs in leaves of higher insertion levels. Conductance had a linear relationship with width x frequency but not with pore area. 相似文献
130.
Mesophyll cells were isolated from sunflower leaves by an enzymic procedure. The cell suspensions possessed high photosynthesis rates. The products of cell photosynthesis were similar to the products of leaf disc photosynthesis. The relatively high radioactivity incorporated into malate after 14CO2 feeding suggests that PEP carboxylase might participate in CO2 fixation. Sunflower leaf extracts possessed a PEP carboxylase activity slightly higher than that of other C3 species. Inhibition of PEP carboxylase by maleate decreased cell photosynthesis by only 15% and the first products of cell photosynthesis were phosphorylated compounds. It is concluded that the high photosynthesis rates displayed by sunflower are not due to a parallel C4 pathway of photosynthesis but are rather dependent, at least in part, on the activity, or the amount, of RuBP carboxylase.Abbreviations PVP
polyvinylpyrrolidone
- PDS
potassium dextran sulfate
- DTT
dithiothreitol
- PEG
polyethyleneglycol
- RuBP
ribulose 1,5-bisphosphate
- PEP
phosphoenolpyruvate
- Mes
2-(N-morpholino) ethanesulfonic acid
- Hepes
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid 相似文献