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Open access

Makoto Kawase

Abstract

Ethylene concentrations in leafless softwood cuttings of Malus robusta and Ligustrum obtusifolium and in leafy cuttings of Chrysanthemum morifolium increased in non-submerged controls steeped upright in water 2.5 cm deep for 20 hr. Increase in ethylene concn was greater in submerged cuttings than in controls.

Ethylene concn in fruits of Malus pumila ‘Red Gold’ and ‘Jonathan’ increased during 24 hr submersion. In Lycopersicon esculentum, however, submersion decreased ethylene concn in both young and mature fruits. Ethylene concn in bulbs of Tulipa fosteriana ‘Red Emperor’ increased in those submerged and the control, but with no significant difference between them. In bulbs of Tulipa gesneriana ‘Peach Blossom’ and tubers of Solanum tuberosum ‘Katahdin’, no ethylene gas was detected either before or after submersion.

Flooding the bases of intact plants of Chrysanthemum morifolium, Helianthus annuus, Lycopersicon esculentum, and Raphanus sativus for 24 hr increased ethylene concn in submerged stems and roots, while it did not change ethylene concn in controls. When roots and basal stems of Chrysanthemum morifolium and Helianthus annuus plants were flooded, ethylene concn in non-flooded stems adjacent to flooded stems also increased. When the bases of intact Lycopersicon esculentum plants were flooded, ethylene concn was greater in the lower half of the submerged portion than in the upper half.

Open access

Makoto Kawase

Abstract

Water soluble rooting substances were obtained from selected woody ornamentals by the centrifugal diffusion method from the cuttings, or by the water extraction method from the ground freeze-dried cuttings. Species used were Cotoneaster racemiflora soongorica, Euonymus fortunei carrierei, Ilex opaca, Lonicera maacki, Physocarpus amurensis, Symplocos paniculata, Taxus cuspidata, Viburnum burkwoodi, and V. opulus. The centrifugal diffusates from Cotoneaster racemiflora soongorica, Euonymus fortunei carrierei, and Symplocos paniculata promoted rooting of mung bean cuttings. Generally the centrifugal diffusates from all of the species studied contained 4 root-promoting fractions with Rf’s, in isopropanol:ammonia:water, of 0–0.1, 0.2–0.4, 0.6–0.8, and 0.8–1.0. All of these fractions promoted rooting of mung bean cuttings without added indole-3-acetic acid. The fraction at Rf 0-0.1 caused the strongest root promotion. Similar results were found in the water extract from the freeze-dried materials. The results strongly suggest that diffusible and water-soluble rooting substances commonly exist among many species of woody plants.

Open access

Makoto Kawase

Abstract

Most agricultural crops are mesophytes which require an environment which is neither too wet nor too dry for maximum growth and productivity. Once soil becomes waterlogged, air space is displaced with water. The O2 remaining in the soil, either dissolved in water or trapped in air cavities, is quickly depleted by respiration of plant roots and soil microorganisms (69). O2 replenishment in the soil is very inefficient because of the stow diffusion of atmospheric O2 into the waterlogged soil. Root systems are thus suddenly plunged into an anaerobic condition by waterlogging. If waterlogging continues for a tong period, the reducing processes in the rhizosphere aggravate the plant condition. Waterlogging does not necessarily occur only when the soil is inundated. Rather, waterlogging often occurs when water fills a critical proportion of the soil air spaces, depending upon the species of the plant involved. Such problems are prevalent in fields having poor drainage, that is, when underground and surface drainage is inadequate to remove water from the soil after a rain.

Open access

Makoto Kawase and Hitoshi Matsui

Abstract

When hypocotyls of intact ‘Red Kidney’ beans (Phaseolus vulgaris L.) were wrapped with black plastic sheets, visible root primordia appeared within 12 days. No root primordium appeared in hypocotyls wrapped with clear plastic sheets. Etiolation did not stimulate formation of root primordium when shoots above the cotyledons were removed, but stimulated formation when shoots were replaced with lanolin containing indoleacetic acid (IAA), indolebutyric acid (IBA), or naphthaleneacetic acid (NAA). Even non-etiolated hypocotyls produced root primordia when auxin concentration in the lanolin was high. Etiolation treatment was more effective in root primordium formation when auxin supply was low. Pretreatment of hypocotyls with etiolation with shoots above the cotyledons removed did not stimulate the formation of root primordium in subsequently detached hypocotyl cuttings. Etiolation treatment did not significantly change the auxin concentration in the etiolated parts. These results suggest that etiolation stimulated root initiation by increasing the sensitivity of the stem to auxin.