Growth and Differentiation of Plant Tissue Cultures: I. Changes Accompanying the Growth of Explants from Helianthus tuberosus tubers

Explants derived from artichoke tubers proliferate rapidly whencultured aseptically on a nutrient medium containing sugar,mineral salts, coconut milk, and 2, 4 dichlorophenoxyaceticacid. This rapid growth, which occurs in three distinct stages,is accompanied by massive changes in numbers of cells, freshand dry weight, and pronounced changes in the rates of gaseousexchange. The very short lag phase is followed by a period ofexponential cell division during which the original cellularpattern is partially obliterated. At the end of this growthphase redifferentiation occurs, tracheidea are formed in largenumbers, and distinctive nodular bodies appear which resemblemeristems. Under the conditions of these experiments they donot develop further.     

Field assessments of resistance to the aphids Sitobion avenae and Metopolophium dirhodum in old and modern spring-sown wheats

Three ancient varieties of wheat and two modern spring-sown cultivars were investigated in the field to assess their resistance to the cereal aphids Sitobion avenae and Metopolophium dirhodum; the monitoring of natural populations and detailed observations using clip-cages were both undertaken. The ancient variety Einkorn showed both antixenotic and antibiotic resistance to S. avenae, and antibiotic resistance to M. dirhodum. The resistance to S. avenae was greater than that to M. dirhodum. The value of Einkorn as a component of a resistance-breeding programme is discussed with reference to its agronomic and genetic characteristics and with reference to the pest status of cereal aphids.     

Description of Cydia piceicola,sp. nov. (Lepidoptera,Tortricidae), feeding on Picea jezoensis in Korea

The adult and the early stages of Cydia piceicola, sp. nov., are described and illustrated from Korea. Larvae of the new species feed on Picea jezoensis (Siebold et Zucc.) Carrière, The life history and larval feeding habits are briefly discussed.     

Taxonomic review of the genus Aulacorthum (Sternorrhyncha: Aphididae) for the Korean peninsula, with the description of one new species

Twelve species of the genus Aulacorthum Mordvilko 1914 (Sternorrhyncha: Aphididae) are recognized from the Korean Peninsula. One new species, Aulacorthum ixeridis n. sp., is described for apterous and alate viviparous females on Ixeris chinensis var. graminifolia (Ledeb.) H. C. Fu and Lactuca indica L. (Asteraceae). From the allied species, Aulacorthum nepetifolii Miyazaki 1968, Aulacorthum ixeridis n. sp. is distinguished by the relatively short ultimate rostral segment (0.83–1.07 × as long as the second segment hind tarsus), the dense spinules on head and the triangular short cauda. Host plants of the Korean Aulacorthum are reviewed and the identification key to subgenera and species is also presented.     

Plant speciation on tropical mountains: Leptospermum (Myrtaceae) on Mount Kinabalu, Borneo

The genus Leptospermum (Mytaceae) is represented on Mount Kinabalu, Borneo, by L.flavescens (widespread on Malesian mountains and uplands) and L.recurvum (endemic to Mount Kinabalu). Analysis of the general morphology, leaf characters, leaf anatomy and flavonoid content of field collection, of both taxa at 1970–4000 m indicated that L.recuruum is a distinct species, most probably derived from L.flavescenS. L.recurvum individuals display a striking variation in leaf pubescence. Seedlings of. These plants grown under uniform conditions were not genetically variable (as seen in the uniformity of peroxidase and acid phosphatase isozymes).Variation that did occur was not correlated with altitude or any other identifiable ecological factors. The sporadic distribution of individuals producing non-viable seeds, probably an expression of genetic load, is another indication of a lack of genetic diversity. L.recurvum may have evolved from a population of L.flaurscens on Mount Kinabalu, most probably during the Pleistocene.     

Variations in Root Water Potentials: Influence of Environmental Factors for Two Succulent Species

Average root water potential (