Luisa Martin

Differences in the contents of total sugars, reducing sugars, starch and sucrose in embryogenic and non-embryogenic calli from Medicago arborea L.

The total sugars, reducing sugars, starch and sucrose in embryogenic and non-embryogenic calli from explants (cotyledons, petioles, hypocotyls and leaves) obtained from Medicago arborea L. seedlings were evaluated. Total sugars were the major components in the calli and no significant differences between embryogenic and non-embryogenic calli were observed. In contrast, important differences between the embryogenic and non-embryogenic calli were observed for reducing sugars, the highest levels being observed in embryogenic calli. The highest starch levels were found in non-embryogenic calli developed in MS medium. During the development of somatic embryogenesis very low starch levels in the callus were found. During the first months of culture, no significant differences in the sucrose content were found between calli that produced embryos and those that did not. The most important differences in sucrose were seen between calli transferred to medium F0, which had the greatest embryogenic capacity, and those transferred to medium F6, which inhibited embryogenesis. In the latter case, an increase in sucrose was observed.

Cytokinins in chick-pea seeds identification and transformation during germination and seedling growth

Summary Eight cytokinins were detected in germinated chick-pea ( Cicer arietinum L. var. Castellana) seeds. Treatments of extracts with β-glucosidase revealed the presence of two cytokinin glycosides: zeatin glucoside and glycosil zeatin riboside. Treatment with potassium permanganate allowed the differenciation of dihydrozeatin and dihydrozeatin riboside. These dihydro forms are present at advanced stages of germination.

Variation of the Levels and Transport of Cytokinins during Germination of Chick-pea Seeds

Summary Cytokinins detected in chick-pea seeds were present in the embryonic axes and first appeared in the cotyledons after 12 hours of germination. The appearance and initial increase of cytokinins in cotyledons is common to both the free and bound forms. However, from 24 hours of germination onwards the disappearance of bound cytokinins is much faster than that of the free forms, suggesting transformation of the bound forms into free ones during this stage of germination. The cytokinins detected in the cotyledons seem to originate from the embryonic axes, though there is no passage of these substances from the cotyledons to the axes. The β-glucosidase activity measured both in cotyledons and in embryonic axes, was seen to be positively correlated with the decrease in bound cytokinins and the increase in free forms, suggesting the transformation of cytokinin glycosides into their corresponding free forms.

Effects of high temperature on the variation and transport of endogenous cytokinins during the germination of Chick-pea seeds

Summary Chick-pea seeds have an optimal germination temperature of 25°C. A temperature of 30°C induces a delay of approximately 24 hours in the germination of these seeds and also a 24–36 hours delay in the appearance of cytokinins in the cotyledon, the transformation of glycosides into free bases and of free bases into dihydroderivatives. The transport of cytokinins from the axis to the cotyledon also undergoes a similar delay and as at 25°C no passage of cytokinins from the cotyledon to the embryonic axis can be detected. On the 5th day of the period studied, the delay occurring in germination and levels of cytokinins as compared with normal conditions is less pronounced, there already being a diminished effect of high temperature. The cytokinins evaluated and identified when the seeds were germinated at 30°C were the same as those observed when germination took place at 25 °C.

Effect of dihydrozeatin on the mobilization of protein reserves in protein bodies during the germination of chick-pea seeds

Summary During the germination of chick-pea seeds, the absence of the embryonic axis markedly reduces the degradation of proteins located in protein bodies. All the enzymes studied - aminopeptidase, carboxypeptidase and caseinases - were found both in the albumin fraction and in the fraction of membrane-bound proteins (MBP) of the protein bodies. In the absence of the axis, an important degree of inhibition was observed in the different proteinase activities, with the exception of carboxypeptidase activity, which exhibited values very close to those obtained in protein bodies of cotyledons of seeds germinated in the presence of the embryonic axis. The application of dihydrozeatin led to an increase in protein degradation, mainly of the globulins, thus exerting an inductor effect on the different proteolytic activities when the hormone was applied to excised cotyledons. Only the aminopeptidase activity seemed to be regulated by the presence of dihydrozeatin.

The effect of dihydrozeatin on the mobilization of protein reserves in the cotyledons of chick-pea seeds

Summary In chick-pea seeds, the axis seems to have a clear regulatory role in the processes involved in protein degradation since in its absence very little protein degradation is recorded. However, its effect on proteolytic enzymes varies according to the enzyme studied, as does the pH at which each of these enzymes exhibits its maximal activity. The application of dihydrozeatin during the incubation of seeds whose embryonic axis has been excised increases globulin degradation. The dihydrozeatin does not seem to have any effect on aminopeptidase activity while caseinolytic and carboxypeptidase activities are affected by this hormone.

Influence of endogenous cytokinins on reserve mobilization in cotyledons of Cicer arietinum L. Artificial restoration of endogenous levels of isopentenyl adenine riboside and isopentenyl adenine

Abstract Of the eight endogeneous cytokinins detected in cotyledons of Cicer arietinum L. seeds, isopentenyl adenine riboside exerts its main effect on the metabolism of reserve lipids and is less efficient with respect to the metabolism of carbohydrates and proteins. Isopentenyl adenine only has a regulatory effect on carbohydrate metabolism.

GIBBERELLIN-LIKE ACTIVITY OF SOME TETRACYCLIC DITERPENOIDS FROM ELAEOSELINUM SPECIES AND THEIR DERIVATIVES

Abstract The growth-regulatory activity of 13 tetracyclic diterpenoids with kaurane, beyerane and atisane skeletons isolated from Elaeoselinum species (Umbelliferae) has been tested in six bioassays and their activities were compared with that shown by gibberellic acid, GA 3 . Seven of the tested substances showed an activity similar or greater than that displayed by GA 3 at concentrations 1 to 10 μg ml −1 . The most active compounds are ent -15α-angeloyloxykaur-16- ene-3β-yl acetate, methyl ent -18-angeloyloxykaur-16-ene-19-oate, methyl ent -beyer-15-ene-19-oate, methyl ent -14pβ- tygloyloxybeyer-15-ene-19-oate (methyl elasclepiate) and ent -beyer-15-ene-14β,19-diol.

Effects of Red light and Far-red light on the Variation and Transport of Endogenous Cytokinins during the Germination of Chick-pea seeds

Summary The type of cytokinins evaluated and identified when seeds were germinated with red light and with red light followed by far-red light were the same as those observed when germination was carried out in darkness. Red light affected the behaviour of endogenous cytokinins. An increase was observed in the appearance of free bases in the cotyledons paralleled by an increase in the transport of these substances from the axis to the cotyledon. Lower levels of free bases and glycosides were found in the embryonic axis accompanied by a delay in the transformation of zeatin and zeatin riboside into their dihydro forms. Under this kind of treatment a transport of dihydro forms from the cotyledon to the embryonic axis was also observed which is absent in darkness. Far-red light applied after red light treatment reversed the effects of the latter wich indicates the involvement of phytochrome in the processes responsible for the accumulation and transport of cytokinins. However, in cotyledons, far-red light does not reverse the advance caused by red light in the transformation of zeatin and zeatin riboside into their dihydro forms.

Analysis of lipids and fatty acids during the germination of Brassica campestris cv. esculenta seeds

Abstract Turnip tops seeds have a high lipid content (47.22% dry wt.); there is clear predominance of neutral lipids, mainly triglycerides, which represent 71.8% of the total lipid content. These triglycerides decrease during germination, with a maximum descent taking place between the 5th and 6th days of germination; this coincides with the maximum content in fatty acids in the seeds. However, phospholipids and glycolipids increase gradually during the same period. Gas-chromatography studies of the total and free fatty acids of these seeds reveals a predominance of those with an even number of carbon atoms; the proportion of unsaturated fatty acids is greater than that of the saturated kind. Among the former, of note are the high proportions mainly of erucic acid and oleic acid present in many seeds of the Cruciferae; the main saturated fatty acids found are palmitic, stearic and behenic acid.