Effects of Salinity on the Extensibility and Ca Availability in the Expanding Region of Growing Barley Leaves

The growth of barley (Hordeum vulgare L.) leaves is reduced by salinity. We used the Instron extensometric technique to measure the reversible and irreversible compliance of the expanding regions of growing barley leaves from plants exposed to 1, 40, 80 and 120 mM NaCl in nutrient solution. Two barley cultivars differing in salinity resistance (cv ‘Arivat’ and cv ‘Briggs’) were compared over 5d of leaf growth. During the period of most active leaf expansion, salinity reduced reversible compliance and increased compliance in the leaf segments, although responses to salinity were complex and changed over the course of leaf expansion. Salinity increased irreversible compliance more in the salt-sensitive cultivar Arivat than in the more salt-tolerant cultivar Briggs. Elemental analysis of the basal leaf segments used for extensometry revealed an accumulation of Na and a depletion of Ca in segments from salinized plants, resulting in very high Na: Ca ratios in salinized expanding tissue. The concentrations of K and Mg in basal leaf tissue were elevated by salinity. Our data do support the hypothesis that the inhibition of leaf expansion by salinity stress is mediated by a decline in irreversible extensibility. We suggest that reduced Ca availability in expanding leaf tissue may contribute to growth reduction in salt-stressed barley seedlings.     

Canopy photosynthetic production in a Japanese larch stand. I. Seasonal and vertical changes of leaf characteristics along the light gradient in a canopy

In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area growth curve was 0.155–0.175 day⁻¹, while that for the weight growth was 0.112–0.117 day⁻¹. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm² g⁻¹ and then decreased until it leveled off at about 140 cm²g⁻¹. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I ₀) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I ₀)+B andb=C/(I′/I ₀)+D. Leaf respiration rate was also increased with increasingI′/I ₀. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear regression on semilogarithmic co-ordinates.     

A revised infrageneric classification of Nothofagus (Fagaceae)

HILL, R. S. & READ, J., 1991. A revised infrageneric classification of Nothofagus (Fagaceae). An examination of cupule morphology, leaf architecture and cuticular morphology of Nothofagus species demonstrates that the existing infrageneric classifications are inaccurate. Four subgenera are proposed, based on these characteristics as well as other morphological information. This analysis indicates that the traditional pollen groupings of Nothofagus closely reflect the infrageneric taxonomy. It is hypothesized that deciduousness is primitive in Nothofagus , and the evergreen habit has arisen more than once, and therefore the deciduous or evergreen habit is invalid as a primary taxonomic character.     

Distribution and immunolocalization of stachyose synthase in Cucumis melo L.

Indirect evidence for the site of stachyose biosynthesis has been provided by determining the occurrence and distribution of stachyose, raffinose and galactinol, the donor of the galactosyl moiety for stachyose synthesis, in Cucumis melo L. cv. Ranjadew. Studies of enzyme activities for the synthesis of these sugars and their distribution in different plant organs and isolates has led to the conclusion that stachyose is synthesized mainly in mature leaves and seeds. Nevertheless, stachyose-synthase activity varied with leaf age, the developmental stage of a plant, the growing season and the plant cultivar used. No stachyose or stachyose-synthase activity could be detected in isolated mesophyll protoplasts and chloroplasts, whereas both were found in a minor-vein-enriched fraction isolated from mature leaves. The conclusion that stachyose biosynthesis is associated with minor veins was confirmed by immunolocalization of the enzyme. Positive specific immunoreactivity of stachyose synthase with polyclonal anti-stachyose-synthase antibodies, labeled with protein A-gold, was detected in intermediary cells of leaf minor veins. The implication of this local synthesis of the main transport sugar for phloem loading in mature leaves of Cucumis melo is discussed.Abbreviation RUBPCase ribulose-1,5-bisphosphate carboxylase This work was supported by Deutsche Forschungsgemeinschaft. The excellent assistance of Ms. B. Müller in preparing the samples for electron microscopy is gratefully acknowledged. The authors thank Professor H.J. Schneider-Poetsch for anti-RuBPCase antibodies.     

Epidermal conductance in different parts of durum wheat grown under Mediterranean conditions: the role of epicuticular waxes and stomata

Abstract. Epidermal (non-stomatally-controlled) conductance from the fourth leaf, first node leaf, flag leaf and ear of durum wheat (Triticum turgidum var durum L.) grown under Mediterranean field conditions has been measured, along with leaf stomatal frequency and the amount and distribution of epicuticular waxes. Measurements were carried out on varieties and land-races from the Middle East, North Africa, ‘Institut National de la Recherche Agricole’ (INRA) and ‘Centra Internacional de Mejora de Maiz y Trigo’ (CIMMYT). Significant differences were observed among genotypes in the epidermal conductances (g_e) of the four organs. For each of the four organs tested, genotypes from the Middle East and CIMMYT showed higher g_e. values than those from North Africa and INRA. Ears showed epidermal conductances that were more than four times higher than those of leaves when g_e. values were expressed per unit dry weight. The amount of epicuticular waxes was higher in the fourth leaves, intermediate in the first node and flag leaves and lower in the ears. For each organ, g_e differences among genotypes were unrelated with the amount of epicuticular waxes. Removal of epicuticular waxes by dipping the organs into chloroform significantly increased the epidermal conductance for the fourth and first node leaves and the ear. However, this did not occur for the flag leaf. For the fourth leaf, g_e of intact leaves and g_e of leaves in which epicuticular waxes were removed were unrelated (r = -0.265). The regression coefficient of this relation for the first node and flag leaves showed values of 0.666 and 0.650 (P > 0.05), respectively, and values were even higher in the ear (r > m 0.892, P > 0.01). Scanning electron microscope analysis showed that wax bloom decreased from the fourth leaf to the flag leaf, whereas the extent of amorphous wax increased. Wax bloom in leaves consisted mainly of deposits of thin wax plates. In the ears and the adaxial surface of flag leaves, fibrillar waxes predominated. In the first node and flag leaves, the wax deposits on the adaxial side cover the surface of the leaf more densely and uniformly than those on the abaxial side. There was no significant correlation between g_e and total stomatal density, or between g_e and either adaxial or abaxial stomatal density for any sample of the three different leaves. The contribution of epicuticular waxes plus total stomatal frequency only explained 42.4, 11.8, 28.3 and 16% of g_e (per unit leaf area) variations for the fourth leaf, first node leaf, flag leaf and the combined variation of the three leaves together, respectively. From these results, it is concluded that complex interrelationship between different morphophysiological characteristics probably control g_e differences among genotypes and that these interrelationships differ for each different plant part.     

Transformation of Nicotiana tabacum,N. debneyi,and N. rustica: Inheritance and protoplast expression of antibiotic resistance

Agrobacterium tumefaciens strains harbouring plasmid vectors pBCAT1, pVU1011 or pMON806 were used to transform leaf explants of Nicotiana tabacum cultivars Delgold and Candel, N. debneyi, and N. rustica var. NRT. Transgenic plants resistant to the selective agents kanamycin, hygromycin or methotrexate were regenerated and used as sources of leaf mesophyll protoplasts. Protoplasts divided and regenerated plants in the presence of selective agents at levels inhibitory to protoplasts of non-transformed plants. Cross-resistance of protoplasts to more than one selective agent was not observed in this study which suggests that this approach may lead to an efficient interspecific somatic hybrid selection system.     

The expression of PS integrins in Drosophila melanogaster imaginal disc cell lines

Summary Drosophila imaginal disc cell lines show a characteristic pattern of aggregation in culture, which appears to be due to cell-cell rather than cell-substrate interactions. We have examined the distribution of PS integrins in wing and leg cell lines, and find that these integrin homologues are expressed preferentially in aggregates. Cell sheets, small cell clumps and chains of cells express antigen at points of cell-cell contact only.