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Three Fortunella (kumquat) species, the Meiwa kumquat (F. crassifolia Swingle), the Round kumquat [F. japonica (Thunb.) Swingle] and the Changshou kumquat (F. obovata hort. ex Tanaka), showing tetraploid, which had been induced by treating the seeds with colchicine, were examined for origin and horticultural characteristics (e. g. morphology of leaves, flowers, pollen and fruits). Additionally, these tetraploid kumquats were crossed to produce triploid kumquats. All of the tetraploids were confirmed to be derived from the nucellar embryo of each original kumquat by examining their chromosomal composition with chromomycin A3 staining. All of the tetraploid kumquats had the typical morphological characteristics of tetraploid Citrus plants, such as round and thick leaves, and large flowers and pollen grains. On the other hand, the fruits of these tetraploid plants showed desirable traits for kumquats such as thicker pericarp and higher soluble solids content. Furthermore, when these tetraploids were crossed with some diploid cultivars, triploid progenies were obtained from almost all of the cross combinations.

A ploidy chimera of the Meiwa kumquat (Fortunella crassifolia Swingle), which had been induced by treating the nucellar embryos with colchicine, and had diploid (2n = 2x = 18) and tetraploid (2n = 4x = 36) cells, was examined for its ploidy level, morphological characteristics, and sizes of its cells in its leaves, flowers, and fruits to reveal the ploidy level of each histogenic layer. Furthermore, the chimera was crossed with the diploid kumquat to evaluate the ploidy level of its reproductive organs. The morphological characteristics and the sizes of the cells in the leaves, flowers, and fruits of the chimera were similar to those of the tetraploid Meiwa kumquat and the ploidy periclinal chimera known as “Yubeni,” with diploids in the histogenic layer I (L1) and tetraploids in the histogenic layer II (L2) and III (L3). However, the epidermis derived from the L1 of the chimera showed the same result as the diploid Meiwa kumquat in all organs and cells. The sexual organs derived from the L2 of the chimera were significantly larger than those of the diploid. Moreover, the ploidy level of the seedlings obtained from the chimera was mostly tetraploid. In the midrib derived from the L3, the chimera displayed the fluorescence intensity of a tetraploid by flow cytometric analysis and had the same size of the cells as the tetraploid and the Yubeni. According to these results, the chimera is thought to be a ploidy periclinal chimera with diploid cells in the outermost layer (L1) and tetraploid cells in the inner layers (L2 and L3) of the shoot apical meristem. The chimera had desirable fruit traits for a kumquat such as a thick pericarp, a high sugar content, and a small number of developed seeds. Furthermore, triploid progenies were obtained from reciprocal crosses between the chimera and diploid kumquat.

Juice vesicle explants of satsuma mandarin cultured on MS solid medium grew expansively and their weight increased 250–400% over a month and accumulated sugar (50–90 mg/g juice). However, sugar accumulation did not occur when one-third of fruit was cultured. Sugar accumulation only occurred in the juice vesicle explants excised from fruitlet later than 51 days after full bloom and cultured on a medium containing 10% sucrose. Supplements of benzyladenine (BA), gibberellic acid (GA3) or naphthalene acetic acid (NAA) in the medium promoted the growth of juice vesicles, but these growth regulators did not stimulate sugar accumulation. Effects of sucrose, glucose and fructose on vesicle growth and sugar accumulation were determined. Fructose was not effective for vesicle growth. Total sugar content in juice vesicles was highest on the medium containing glucose. Sugar composition in vesicles cultured on various carbohydrates indicated that sugar degradation and conversion occurred in vesicle explants.

Sugar contents in the juice and peel of very early to late ripening satsuma mandarin cultivars were determined by HPLC. There was little difference in the seasonal change in the juice sugar contents among eight cultivars. In all cultivars there was a peak of glucose : fructose ratio during ripening, which was not related with ripening time of these cultivars. In 'Miyagawa Wase' (early ripening) and 'Aoshima' (late ripening), the sucrose content in the juice began to increase in September. However, an increase of total sugar content in the peel of 'Aoshima' was delayed compared to that of 'Miyagawa Wase', but the pattern of sugar accumulation by the juice differed little among the satsuma mandarin cultivars.

Satsuma mandarin trees were water-stressed severely (WS-s) and moderately (WS-m) by withholding in autumn. Sugar contents of juice and peel were determined by HPLC.Sucrose and reducing sugars in the juice and peel were increased by the water stress treatment, notably, fructose in the peel. Increase of sucrose in the juice and peel was inhibited by WS-s. Total and reducing sugar concentrations in the peel from the WS-s plot were lower than those from the WS-m plot at harvest on November 26.Although the sugar content of the stylar end of the fruit was greater than that of the stem end, the % reducing sugars in the stem end was consistently higher than that of the stylar end. This relationship was not changed by water stress treatment.The peel color gradient from the stylar to the stem ends paralleled that of the sugar gradient; the gradient for titratable acidity was the reverse.

The minimum explosive concentration and ignition energy of several kinds of cellulose derivatives-methylcellulose, hydroxypropyl methylcellulose, low-substituted hydroxypropylcellulose, hydroxypropyl methylcellulose phthalate and hydroxypropyl methylcellulose acetate succinate-were measured to evaluate their potential for dust explosion.It was found that the explosibility of cellulose derivatives increased with a decreasing average particle size or bulk density and an increase in the amount of fibrous particles. These factors were expressed in a specific surface area. Moreover, the dust explosibility increased with a higher total molecular of substitution in the cellulose unit. However, it was hardly affected by the kind of substituents nor the average molecular weight of the cellulose derivatives.

The experiment was undertaken to promote an enlargement of frost-induced seedless loquat fruit through applications of gibberellic acid (GA) and GA combined with N- (2-chloropyridyl) -N'-phenylurea (KT).Spraying with an aqueous solution of 500 ppm GA or 500 ppm GA+20 ppm KT greatly stimulated frost-induced seedless fruit to attain the same size as seeded control ones. The GA-treated seedless fruits were more slender but had a thicker pulp, compared to seeded untreated fruits. Application of GA + KT was more effective for enlargement than a single application of GA. If sprayed immediately after a frost, the enlargement response of the seedless fruits was significant. Although treated seedless fruits turned yellow earlier, the total soluble solids contents in the juice at harvest were slightly lower than that of seeded fruits. No difference in titratable acidity was found between the treated and control fruits.

Juice vesicle explants including some mesocarp tissue excised from young satsuma mandarin (Citrus unshiu Marc. cv. Miyagawa wase) fruit, were cultured in vitro on MS solid medium supplemented with 1 mg/L BA and 5 or 10% sucrose under dark conditions at 25°C. The juice vesicles grew expansively and turned orange. The juice vesicles accumulated sugar when cultured on the medium supplemented with 10% sucrose and incubated for two months. Sugar composition in the cultured juice vesicles differed from that of fruit grown in the field. The in vitro culture of juice vesicles may aid in elucidating the mechanism of sugar accumulation and other compounds in Citrus fruit.

Using pot-grown Wase satsuma mandarin (Citrus unshiu Marc.) trees grafted on trifoliate orange (Poncirus trifoliata Raf.) and Natsudaidai (C. natsudaidai Hayata) seedlings, the effect of water stress on cold hardiness was examined by withholding water in varying periods of time from fall to winter. Freezing tests were conducted at intervals during the withholding of water to evaluate cold hardiness. Water relations and carbohydrate and proline contents in plant parts were also determined. Almost the same results were obtained with both species and are summarized as follows.1. Transpiration and leaf water potential of water-stressed trees were always lower than in non-stressed (irrigated) ones, though those characters in the non-stressed trees declined gradually from November to January.2. Freezing tests done in November and December revealed that water stress given beforehand increased cold hardiness. However, freezing tests in January, when even non-stressed trees were already hardened sufficiently by natural low temperature, demonstrated that the trees stressed from October or November on were less hardy compared to non-stressed controls, though the trees stressed from December on were somewhat hardier.3. Water stress increased proline contents in leaves, stems and roots while it reduced starch contents. Total sugar contents in November and December in the trees stressed earlier were higher than in non-stressed ones. However in January, sugar contents in the leaves and stems of the trees stressed from October or November on were lower than in the trees non-stressed or stressed from December on. These sugar changes were closely related to the changes in cold hardiness.4. In conclusion, it is suggested that under relatively warm temperature conditions from fall to early winter, water stress induces cold hardening, but that in mid-winter when the trees have been naturally hardened, any beneficial effect of water stress given beforehand is diminished or even becomes detrimental.

Using 3-year-old wase satsuma mandarin (Citrus unshiu Marc.) trees grafted on trifoliate orange (Poncirus trifoliata Raf. ), 8-month-old natsumikan (Citrus natsu-daidai Hayata) seedings, and 6-month-old avocado (Persea americana Mill.) seedings, the effect of low root temperatures on cold hardiness was examined in relation to whole-plant water status, changes in carbohydrate and proline concentrations, and endogenous hormone activities in plant parts.Transpiration and leaf water potential in all species were reduced at low root temperatures (5° and 13°C), leaf water potential being most markedly affected at the lower temperature.Total sugars and proline in the leaves, stems, and roots accumulated while starch was reduced at low root temperatures.Cold hardiness in all species was greatly augmented at 5°C root temperature compared to 13°C and the control.Endogenous gibberellin and cytokinin activities in the roots (trifoliate orange) of wase satsuma mandarin were increased when exposed to 5°C root temperature.In conclusion, in both citrus species and avocado lowering root temperature restricts water uptake and then induces cold hardening together with accumulation of sugars and proline in the plant tissues.