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.     

阔叶树的叶形曲线方程：—适于叶面积计算的数学模型

树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在     

八种针阔叶幼树清晨叶水势与土壤含水量的关系及其抗旱性研究

一、前言土壤是植物根系的生活环境,是供给植物赖以生存的水分和养分的源泉。干旱区的植物尤其是树木常常由于土壤供水不足而限制其自然分布和生长。根据土壤-植物-大气连续体系     

Resistance in the wild crop relatives Avena macrostachya and Hordeum bogdani to the aphid Rhopalosiphum padi

In previous screening tests the two wild crop relatives Avena macrostachya (Bal., ex Coss. et Dur.) and Hordeum bogdani (Wil.) demonstrated a high degree of resistance to the aphid Rhopalosiphum padi (L.). In a choice situation using wild and cultivated oats and barley, alate aphids settled in lower numbers on the wild species. The results were, however, variable in the Avena combination. Nymph production was significantly higher, development time shorter and adult weight higher on the cultivated varieties. From the third instar and onwards the excretion of honeydew was significantly lower on the resistant plants. In general the honeydew contained less than 1% free amino acids although excreta from H. vulgare contained 3.5%. The percentage of free amino acids found in the honeydew was similar for all plant species (5.2–7.6%) except for H. vulgare, on which the aphids excreted 22% of the amounts ingested. Amino acids excreted in high proportions on all plants included asparagine, -aminobutyric acid, glutamic acid, and glycine. Tissue sectioning did not reveal any obvious mechanical barriers to stylet penetration. The potential use of these wild species as sources for aphid resistance breeding in oats and barley is considered.

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Résumè Lors d'examens systématiques antérieurs, Avena macrostachya (Bal. ex Coss. & Dur.) et Hordeum bogdani (Wil.) ont présenté une résistance élevée au puceron Rhopalosiphum padi (L.). Lorsqu'ils avaient un choix comprenant de l'avoine et de l'orge cultivés, les pucerons ailés ont atterri en nombres moins importants sur les espèces sauvages. Les résultats étaient cependant variables dans le complexe avoine. La production de nymphes et le poids des adultes étaient plus élevés sur espèces cultivées, ainsi que la durée du développement était plus longue sur les espèces sauvages. A partir du troisième stade, l'excrétion de miellat a été significativement plus faible sur les espèces résistantes. En général, le miellat y contenait moins de 1% d'acides aminés bien que sur H. vulgare il en contînt 3,5%. Les pourcentages d'acides aminés libres du miellat étaient semblables sur toutes les plantes (5,2–7,6%), à l'exception de H. vulgare sur lequel les pucerons excrétaient 22% des taux ingérés. Les acides aminés excrétés en fortes quantités sur les différentes plantes, comprenaient l'asparagine, l'acide -aminobutyrique, l'acide glutamique et la glycine. Des coupes de tissus n'ont révélé aucun obstacle mécanique clair à la pénétration des stylets. Les possibilités d'utiliser ces espèces sauvages comme source de résistance aux pucerons dans la sélection de l'avoine et de l'orge ont été examinées.

     

Pyrrolizidine alkaloids of probable host-plant origin in the pronotal and elytral secretion of the leaf beetle Oreina cacaliae

Oreina cacaliae (Coleoptera, Chrysomelidae) produces in its elytral and pronotal defensive secretion seneciphylline N-oxide together with small amounts of another pyrrolizidine alkaloid tentatively identified as senecionine N-oxide. This is a strong departure from the chemical composition of the defensive secretions in related species, characterized by complex mixtures of cardenolides, synthesized by the beetles from cholesterol. It is suggested that O. cacaliae sequesters the alkaloids from its host-plant, Adenostyles leucophylla. Other specimens of O. cacaliae from far distant populations feeding on Senecio nemorensis, Petasites paradoxus or P. album also produced pyrrolizidine alkaloids, but not O. speciosissima feeding on the same food plants and producing cardenolides. In addition to pyrrolizidine alkaloids, O. cacaliae secretes ethanolamine, which is also found in all the cardenolide-producing species.     

Interacting effects of increased tannin levels on leaf-mining insects

Tannin-rich extracts were painted on leaves of Q. emoryi (Fagaceae) that contained first instar larvae of a leaf miner, Cameraria sp. (Lepidoptera: Gracillariidae, Agrifoliella group), to test the role of tannins in increasing parasitism, while controlling for changes in protein content and physical damage. Miners from leaves that were treated with tannins had higher rates of parasitism by hymenopterans, but decreased mortality from other causes. The negative and positive effects of tannins balanced since overall larval survivorship was equivalent for leaf miners on tannin-enriched and control leaves. The tannin-rich extract also affected larval development because pupal weight was decreased for leaf miners in treated leaves. Tannins can have both adverse and beneficial effects on these phytophagous insects.

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Résumé Des extraits riches en tanins ont été étalés sur des feuilles de Quercus emoryi contenant des chenilles de ler stade de Cameraria sp., pour contrôler l'influence du tanin dans l'accroissement du parasitisme sans modifier la teneur en protéines ni provoquer de dommages physiques. Les mineuses de feuilles traitées avaient des taux plus élevés de parasitisme par les hyménoptères, mais une diminution des autres causes de mortalité. Les effets négatifs et positifs des tanins se sont équilibrés, puisque la survie des mineuses était la même pour les feuilles traitées que pour les témoins. Les extraits riches en tanin ont agi sur le développement larvaire puisque le poids des chrysalides des mineuses de feuilles traitées était plus faible. Les tanins peuvent ainsi avoir des effets nuisibles et bénéfiques sur ces insectes phytophages.