Eliezer Zamski

Seasonal changes in the carbohydrate content of two cultivars of asparagus

Abstract The annual changes in carbohydrate content in the roots of two cultivars of asparagus (Asparagus officinalis L. cultivar UC 157 and cultivar ‘Junon’) grown in the relatively mild winter climate of Israel were studied. During the autumn (August–November) when the ferns senesce and the subsequent winter dormant season (November–February) the roots were characterized by a constant and significant decrease in fructan content in both cultivars, contributing to a loss of over 30% of the stored fructans. During the harvest (February–April) there was a further decline in root fructan content. During the post-harvest period of fern growth, as the unharvested ferns develop and expand, the root fructan content declined to its lowest levels. Following this, there was a sharp and continuous increase in root fructan levels, as well as a transient increase in sucrose levels for the following three summer months (May–August). The general pattern of root carbohydrate changes was similar in the two cultivars, although there were differences of possible physiological significance.

The Effect of Low Temperature and Drought on The Carbohydrate Content of Asparagus

Summary Expanded shoots of asparagus ( Asparagus officinalis ) were found to contain sucrose, glucose, andfructose, while neither starch nor fructans could be detected. On the other hand, storage roots accumulate fructans, in addition to smaller amounts of sucrose, glucose, and fructose, while starch does not accumulate. Exposing asparagus to low temperature (15/5 °C) caused a rapid, short term increase in the sucrosecontent of the shoot and a simultaneous decrease in the fructan content in the roots. Long term low temperature treatment led to a sharp decrease in the sugar content and concomitant senescence of the shoots, whereas the fructan content of the roots increased. Withholding water during the cold treatment initially led to a further increase in the sucrose content ofthe shoot and also in the fructan content of the roots. However, after 50 days of drought in conjunction with low temperature, shoot sucrose content was decreased, root fructan content was unaffected and root sugar levels were increased, as compared with cold treatment alone. Drought in the absence of cold treatment led to sharp decreases in the glucose, fructose, and sucrosecontents of the shoot and in the fructan content of the roots. The results are discussed in terms of the effect of environmental stresses on the carbohydrate balance of asparagus plants.

Premature leaf chlorosis in cucumber associated with high starch accumulation

Summary Premature leaf chlorosis is a physiological disorder observed in winter-grown cucumber plants and is visually distinct from senescence-related chlorosis. Yellow leaves are characterized by high levels of starch and most of the soluble sugars, including glucose, fructose, galactose, galactinol and inositol. Levels of stachyose were found to be similar in healthy and chlorotic leaves. Electron micrographs of yellow leaves showed that plastids were filled with starch and that only traces of the thylakoid membrane structure remained. Starch levels in cucumber leaves followed a diurnal cycle and morning levels were higher following a low-night-temperature treatment (5 °C minimum) as compared with a high-night-temperature treatment (20 °C minimum). These results are consistent with the hypothesis that this form of chlorosis is due to an accumulation of photosynthate in the source leaf and an overaccumulation of starch in the chloroplast. Reduced export from the source leaf in response to low night temperature may be one of the factors responsible for the symptoms.

Growth of rose flower peduncles and effects of applied plant growth regulators

Removal of flower buds results in abscission of peduncles of the rose cv. Nubia and cessation of peduncle growth in cv. Mercedes. Peduncle growth was inhibited when pistils and stamens were removed, but was not affected by removal only of sepals and petals. Growth of the decapitated peduncles of ‘Mercedes’ was partially restored by the application of auxin in lanolin paste on the base of the peduncle and was completely restored by the application of gibberellin, while the combined application of auxin and gibberellin was the most effective for growth restoration. Growth of non-decapitated ‘Nubia’ peduncles was promoted by application of gibberellin or gibberellin and auxin but not auxin alone.Peduncle elongation of both cultivars was not affected by application of cytokinin and the effect of gibberellin was antagonized by combined application with cytokinin. The peduncles strength (resistance to bending) was affected more strongly by auxin than by gibberellin, and most strongly when auxin and gibberellin were combined. The effect of auxin on the strength of peduncles, but not of gibberellin, was antagonized by application of cytokinin. Excised, non-decapitated flowering stems of ‘Nubia’ treated with gibberellin and auxin in situ, showed, recovery of the peduncles from wilting after exposure to heat conditions.

Streptomycin Resistance in Tobacco: II. Effects of the Drug on the Ultrastructure of Plastids and Mitochondria in Callus Cultures

Summary The effects of streptomycin on the fine structure of chloroplasts and mitochondria were studied in callus cultures of diploid tobacco, and with streptomycin resistant calliclones. Streptomycin has caused a reduction in the amount of thylakoids, prevented the formation of starch grains and lipid droplets in the plastids, caused the development of internal reticulum, and has changed the external shape of the plastids. Also, it brought about the swelling of cristae, and caused degeneration and sometimes elongation, of the mitochondria. These phenomena appear to be concentration related. At high concentrations of streptomycin, only reticulum and no thylakoids were observed within the plastids, and two types of mitochondria were also observed. One type appeared degenerated, while the other appeared functional, but with some swollen cristae. In some cases the plastids and the mitochondria appeared very similar, and the plastid reticulum resembled the cristae in the mitochondria. The streptomycin resistant calliclones exhibited their resistance only by their ability to form well defined grana, starch grains and lipid dropletes in the plastids of cells which were grown at high drug concentrations.

Carbohydrate Content of Young Asparagus Plants as Affected by Temperature Regimes

Summary The effects of four temperature regimes on the carbohydrate contents of the shoot and roots of 16-month-old plants of two cvs. of asparagus (cv. UC157 and cv. Junon) were studied. The soluble sugar (sucrose, glucose, fructose) concentration in the shoot was not affected by the temperature treatments and was similar in both cvs. However, the two cvs. differed in their ability to accumulate root fructans under the different temperature regimes. Cv. Junon had the highest root fructan concentration under the 22/17 regime. At higher temperatures its fructan concentration significantly decreased. In contrast, cv. UC 157 was able to maintain high fructan concentrations even at the higher temperature regimes. Young seedlings of the two cvs. (8 weeks old), prior to the onset of root fructan accumulation, did not differ in their responses to each temperature regime. The ability to accumulate root fructans at high temperatures may have practical significance and may potentially be used as a tool for early screening of asparagus bred for different environmental conditions.

Photo- and Thigmomorphogenetic Control of the Attachment of the Ivy (Hedera helix L.) to its Support

Summary Three photomorphogenetic reactions have been established in the climbing stems of the ivy (Hedera helix L.): (a) Unilateral light directs stem growth away from the light source towards the support (Darwin, 1881). (b) Unilateral light depresses the formation of anchoring roots on the exposed side of the stem, but (c) is permissive to and enhances root formation on the opposite, shaded side. The blue region of the spectrum is active in the photomorphogenetic reactions (b) and (c), but smaller effects are induced by red and far-red illumination. Light precludes the formation of anchoring roots during the inductive phase of root initiation. The first photomorphogenetic response results in contact between the dark side of the ivy stem and the support. The evoked contact stimulus enhances root formation. This thigmomorphogenetic reaction is masked by blue light.

MECHANICAL STRENGTH AND ANATOMICAL STRUCTURE OF THE PEDUNCLES OF ROSE (ROSA × HYBRIDA) FLOWERS

ABSTRACT The anatomical differences between the strong flower peduncles of the rose cv. Mercedes and the weak peduncles of cv. Nubia were investigated. More supporting cells with thicker cell walls were found in the xylem elements and phloem fibers of the cv. Mercedes peduncles than in those of cv. Nubia. Secondary increment was observed in the proximal zone of the peduncles of both cultivars. A complete ring of secondary thickening developed in the peduncles of cv. Mercedes, whereas in cv. Nubia the ring was incomplete due to the lack of interfascicular cambium. These differences were correlated with the postharvest tendency to peduncle bending of these two cultivars.

Antomical Aspects of Citrus Abscission — Effects of Ethylene on Leaf and Fruit Explants

The anatomy of abscission has been attracting the attention of researchers in plant science for many years (2), and Hodgon’s pioneer work on the anatomy of leaf abscission (10) in citrus was published as early as 1918. In citrus we can define five abscission zones (AZs): the basal and laminar AZs of leaves, the shoot/peduncle (AZ-A) and calyx (AZ-C) AZs of fruit, and the AZ between style and ovary.

Streptomycin Resistance in Tobacco: IV. Effects of the Drug on the Ultrastructure of Plastids and Mitochondria in Cotyledons of Germinating Seeds*

Summary The effects of streptomycin on the fine structure of chloroplasts and mitochondria were studied in cotyledons of germinating seeds from St-S (streptomycin sensitive) tobacco seedlings. The drug caused a reduction in thylakoid formation in the chloroplasts; prevented the development of normal grana; drastically reduced the formation of starch grains and lipid droplets in the organelle; and caused changesin the external shape of the plastids. In the mitochondria it caused swelling of the cristae, somtimes elongation, and usually degeneration of the organelle. In the St-R701 (streptomycin resistant) mutant, the resistance was expressed mainly by the ability of the chloroplasts to form normal grana in the presence of the drug. The possible biochemical mode(s) of action of streptomycin are discused.