Susumu Kuraishi

Aluminum-Induced Rapid Root Inhibition and Changes in Cell-Wall Components of Squash Seedlings.

Growth of squash (Cucurbita maxima Duch.) roots was significantly inhibited by 1 mM AlCl3 as early as 1 h after the treatment. The growth inhibition was confined to the elongating zone (1–6 mm from the root tip). Chemical analysis of cell-wall polysaccharides from roots revealed that aluminum increased pectin, hemi-cellulose, and cellulose contents after 3 h of treatment. The effect of aluminum on pectin content was found in the elongating zone including the root tip, whereas change in cellulose content was confined to only nonelongating zones. Hemicellulose content increased in all of the regions along the root axis. The increase in the pectin fraction was due to the increases in uronic acids, galactose, and arabinose constituents, whereas hemicellulose content changed due to increases in glucose, xylose, galactose, and arabinose. The results clearly indicate that aluminum rapidly reduced squash root growth by inhibiting cell elongation and altering metabolism of cell-wall polysaccharides in the nonelongating zone as well as in the elongating zone.

Soil Salinity and pH in Japanese Mangrove Forests and Growth of Cultivated Mangrove Plants in Different Soil Conditions

Soil conditions of mangrove forests in southern Japan were found to correlate largely with zonal distributions of the species.Kandelia candel grew in soils with low salinity and low pH,Avicennia marina, Rhizophora stylosa andSonneratia alba in soils with high salinity and high pH, andBruguiera gymnorrhiza in soil with a wide range of pH but limited range of salinity.Lumnitzera racemosa colonized soil with a wide range of pH and medium salinity. Seedlings ofKandelia candel, Bruguiera gymnorrhiza andRhizophora stylosa were planted in soils with differing salinity and pH. Optimum seedling growth ofKandelia, Bruguiera andRhizophora occurred when plants were cultivated in soils similar to those of their natural habitats, suggesting that growth of mangrove species and their zonal distributions were regulated by salinity and soil pH.

Distribution of abscisic acid in different parts of the reproductive organs of tomato

Abstract The distribution of abscisic acid (ABA) in reproductive organs of tomato ( Lycopersicon esculentum Mill. cultivar ‘Zuisyu’) from buds to fruits, was determined. The fresh weights of the pistil and calyx increased nearly two-fold from 5 days before flowering, but their ABA concentrations remained more or less constant. Five days before flowering, the ABA concentration of the stamens and petals were higher, but decreased to about one-sixth on the days of flowering. Ten days after flowering, pollinated ovaries had less ABA than unpollinated ones. In fruits, ABA concentrations changed in the various parts, independent of each other. High concentrations of ABA were encountered in the pericarp, axis and the locule tissue in the early growth stages. Even around 50 days after flowering, the locule tissue had a small peak of ABA concentration. These results show accumulation of ABA in various regions of the flower and the fruit, independently of each other, at specific growth stages, suggesting specific role(s) for ABA in reproductive development.

Changes of abscisic acid and auxin as related to dormancy breaking ofAllium wakegi bulblets by vacuum infiltration and BA treatment

Dormant bulblets of the sterile green onion,Allium wakegi, broke dormancy and sprouted when infiltrated with water for 1 h at the reduced pressure of 25 kPa or when dipped in 20 ppm of benzylaminopurine (BA) for 1 h at normal (100 kPa) or reduced pressure. One day after the treatment, the abscisic acid (ABA) contents greatly decreased in bulblets treated with BA at both reduced and normal pressure as well as in bulblets treated with water at reduced pressure. The ABA content of bulblets dipped only in water at normal pressure remained relatively high throughout the study. Changes in 2-trans-abscisic acid (t-ABA) and IAA content of bulblets showed no correlation with breaking of dormancy. Dormancy breaking ofAllium wakegi bulblets appears to be related to a sharp decrease in ABA content in the bulblets as a result of water infiltration or BA treatment.

Physical measurement of firmness of banana fruit pulp: determination of optimum conditions for measurement

Abstract Stress-relaxation curves were obtained by plunging a conical probe into the pulp of green and yellow banana fruits [ Musa (AAA group, Cavendish subgroup) ‘Giant Cavendish’]. Three stress-relaxation parameters, minimum stress-relaxation time ( T 0 ), relaxation rate ( R ), and maximum stress-relaxation time ( T m ), were calculated from the stress-relaxation curve. Plunging depth and plunging speed varied the parameters. When parameters were fixed, with a plunging speed of 0.5 mm/s and the plunging depth of 0.6 mm, the yellow bananas showed significantly lower T 0 and T m than green bananas. The lower, T 0 and T m can predict the degradation of polymers responsible for the pulp texture. Measurements of stress-relaxation parameters in different parts of banana pulp revealed that the physical properties were not uniform within the same fruit.

Stable soil pH of thai mangroves in dry and rainy seasons and its relation to zonal distribution of mangroves

AbstractSoil characteristics of mangrove forests at Amphur Laemngob, Trat Province, east Thailand were investigated in both dry andrainy seasons. Sonneratia alba, Avicennia alba andRhizophora mucronata mainly grew as seaward mangroves.Rhizophora apiculata, Ceriops tagal, Excoecaria agallocha andBruguiera gymnorrhiza grew as meso mangroves in most cases.Lumnitzera racemosa was found as a landward mangrove. The salinity of the soil in which these 8 species grew was significantly higher in the dry season than in the rainy season. Soil pH did not change irrespective of the season. Each species seemed to grow at inherent soil pH. Bruguiera gymnorrhiza, Sonneratia alba andAvicennia marina were found both in Japan and Thailand. The soil pH of each mangrove species was similar in Japan and Thailand. The soil salinity of each mangrove species in Japan was similar to that in Thailand in the dry season. It was suggested that soil pH and salinity in the dry season are the important factors governing the zonal distribution of mangroves.

Importance of RNA synthesis whthin the lag phase preceding benzyladenine-induced growth of cucumber cotyledons in the dark

Changes in the rate of synthesis of cellular constituents were studied in detached cucumber cotyledons (Cucumis sativus L. cv. Ohio) after treatment with benzyladenine (BA). BA treatment stimulated RNA and DNA syntheses. The stimulation of RNA synthesis occurred within the lag phase preceding BA-induced growth, while that of DNA synthesis came during the growth. On the other hand, the stimulation by BA was not detected for protein and lipid syntheses. 5-Fluorouracil (FU, 10(-3) m) plus thymidine (T, 10(-4) m) did not inhibit the fresh weight increase in both water- and BA-treated cotyledons, while α-amanitin (AM, 10 µg/ml) inhibited it in both. AM added during the first 4 hr effectively inhibited the growth stimulation by BA, but AM added 6 hr or more after BA had almost no effect. FU+T strongly inhibited the incorporation of (3)H-uridine into cytoplasmic ribosomal RNA (rRNA) and brought about labelling in regions other than those of the regular rRNA species on gel electrophoresis. On the other hand, AM had less influence on the synthesis of cytoplasmic rRNA than FU+T. These results indicate that BA stimulates cotyledon growth in the dark through its effect on messenger RNA synthesis within the lag phase of growth and the synthesis of cytoplasmic rRNA is not always necessary for cotyledon growth.

The maximum leaf surface temperatures of the higher plants observed in the Inland Sea area

The maximum leaf surface temperatures (MLSTs) of 126 species of higher plants were measured by means of an infrared thermometer, in the Inland Sea area, southwest of Honshu-Island, Japan, where plants suffered from severe environmental conditions due to an abnormally small amount of precipitation during the summer of 1978. The MLSTs of plants in the summer of 1978 were greater than or equal to those of 1979, when the environmental conditions were not so severe.The MLST measured in this study was 50.4 C for a non-succulent plant (Liriodendron), and 53.1 C for a succulent plant (Agave). Plants with different life forms appeared to have different MLSTs. The average of the MLSTs of conifers deciduous trees, and evergreens were 36.4, 37.7, and 40.3 C, respectively. This order corresponds to the distribution of forests from high to low, latitudes. Also the MLSTs were higher for woody plants than for herbaceous plants. Relatively high leaf temperatures were observed for climbing plants, both herbaceous and woody.Plants with narrow leaves had lower leaf surface temperatures than those with borad leaves. Herbaceous dicotyledonous plants actively growing at the end of the summer of 1978, in full sun at Hiroshima Castle were exclusively those with relatively high leaf temperatures.

Spatial distribution of abscisic acid and 2-trans-abscisic acid in spears, buds, rhizomes and roots of asparagus (Asparagus officinalis L.)

Abstract Changes in the levels and spatial distribution of abscisic acid (ABA) and 2-trans-abscisic acid (t-ABA) were determined in different sections of spears, buds, rhizomes and roots of dark-grown asparagus (Asparagus officinalis L. cultivar ‘Mary Washington 500 W’). In both buds and rhizomes, ABA level was higher in the younger regions where buds would sprout, while in the growing spears, there was a declining gradient from the morphological apex towards the base. Spear tips were characterized by constant high levels of ABA during their elongation. The growth rate was low in the tip region, and showed a large gradient, declining from the zone of elongation (located 15–35 mm from the tip) to the butt region. Once lateral buds began their growth, the content of ABA in lateral buds plus scale leaves associated with the tip region, was the highest among all tested tissues. The levels of the physiologically less active t-ABA, on a fresh weight basis, showed a gradient, declining from the tip to the butt region in all parts, but was less in absolute amounts. These results support the hypothesis that ABA is involved in mobilizing carbohydrate reserves for spear growth.

Abnormal auxin distribution and poor berry setting (coulure) in grapes

Abstract A constant low auxin level was observed in a normally setting trimmed cluster of the tetraploid grape ‘Kyoho’ ( Vitis vinifera L . × Vitis labrusca L.). The basipetal auxin transport in the trimmed cluster was always 2–3 times higher than the acropetal transport during the flowering-period. In a non-treated cluster, showing a tendency towards excessive berry abscission, the auxin level in the apical parts of the cluster fluctuated within the range of 20–70 times that of the auxin content at full bloom. The ratio of basipetal to acropetal auxin transport was nearly unity or less than unity. The results support the hypothesis of apical dominance and auxin gradient in the formation of an abscission zone.