Takao Ichii’s research while affiliated with Kobe University and other places

Seasonal changes of lipid compositions in leaves of Natsudaidai Kawanonatsudaidai' (Citrus natsudaidai Hayata), a cold-sensitive species, and Yuzu 'Tadanishiki' (Citrus junos sieb. ex Tanaka), a frost-hardy species, were studied. Glycolipids were mainly monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) whereas the phospholipids were mainly phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). The main fatty acids in both lipids were palmitic acid (16: 0), stearic acid (18: 0), oleic acid (18: 1) linoleic acid (18 : 2), and linolenic acid (18 : 3). PG contained trans-Δ3-hexadecenic acid (16: 1). PG was less unsaturated phospholipid than were PC and PE, whereas MGDG was more unsaturated than was DGDG. Phospholipid levels (PC and PE) were high during winter in Natsudaidai and Yuzu. The 18 : 3 and 18 : 2 compositions in glycolipid (MGDG) increased and the double bond index (D. B. I.) attained a high level in winter The 18 : 2 and 18 : 3 compositions in phospholipid (PC) increased and D. B. I. approached maximum during winter. Phospholipid contents and 18 : 3 compositions in glycolipid (MGDG) and phospholipid (PC) were higher in Yuzu than they were in Natsudaidai. Sterol contents increased during winter concomitantly with phospholipid and β-sitosterol; the sterols were higher in Yuzu than in Natsudaidai.

Three-year-old trees of some Japanese pear (Pyrus serotina Rehd.) cultivars of different growth habits (extent of apical dominance) were used. Scaffold branches were trained either vertically or laterally.Diffusible indole-3-acetic acid (IAA) levels in the terminal shoot were higher in the order of cultivars ‘Shinsui’ (strong), ‘Kosui’ (intermediate), and ‘Hosui’ (weak) in an early period, which was the reverse order of their branching ability. Scaffold branch orientation per se did not affect diffusible IAA levels in the various parts of the tree.In all cultivars, after bud break, diffusible IAA levels rapidly increased in all parts, especially in the upper part of the tree, showing a downward gradient from the shoot towards the root. A peak level in the shoot, or in the trunk, was reached prior to the period of most rapid extension growth or radial growth, respectively. The reduction of the level commenced first in the shoot, and spread basipetally towards the root. Diffusible IAA levels were associated with an increment of the growth rate rather than with the growth rate.During the growing season, extractable IAA in the cambial regions changed in a similar way to the diffusible IAA level. However, unlike diffusible IAA, extractable IAA increased and maintained a high level during the non-growing season. Removal of all shoots after cessation of the extension growth markedly decreased diffusible and extractable IAA levels in the rest of the tree.

The stylar proteins of 22 varieties of Japanese pear (Pyrus serotina Rehd., 21 selfincompatible and one self-compatible) were analyzed by isoelectric focusing-polyacrylamidegel electrophoresis (IEF-PAGE) to identify the S-allele proteins (S-proteins) associated withself-incompatibility (SI). The corresponding relationships between the protein bands and thefour alleles S2, S3, S4 and S5, were examined for each variety for which the allele composition was already known.Experiment 1 comprised the IEFs on the four major varieties. Analysis of the band patterns, isolated at intervals pH 310, 58 and 46.5 revealed that three bands (hereafter, tentatively referred to as) (a) at isoelectric point (pI) 6.6, (c) at pI 5.3 and (d) at pI 5.0 werethe putative proteins corresponding to the S4 allele. Band (b) at pI 5.6 and (e) at pI 6.0 werealso the putative proteins corresponding to the S2 allele and the S5 allele, respectively. Allthe bands described above exhibited a positive periodic acid Schiff's (PAS) reaction. Thereforethe presence of glycoproteins was suspected. Experiment 2 comprised IEFs on the other 18varieties. The results compiled from both experiments showed that among 21 varieties (otherthan one self-compatible variety), the correspondence between the bands and S-alleles wasrelatively high on band (c) in 19 varieties. This band was thought to be associated with theS4 allele. Other bands demonstrated rather low correspondences; band (a) exhibited the relationship in 15 varieties, band (b) in 13 varieties and band (d) in 13 varieties. No differencein protein band patterns was exhibited between the self-incompatible variety 'Nijisseiki' andits self-compatible strain 'Osa-Nijisseiki', which was assumed to be a stylar part mutant ofthe S-gene. Our discussion compares the results of this study with research on S-proteinsin other species, and includes suggestions for future research methods.

The stylar transmitting tissue in the mature pistil of the Japanese pear consists of its component cells and intercellular heterogeneous secretions. The cytoplasm of the periplasmic region contains two different organelles that are characteristic of floral bud development. One of these is the vesicle, which is derived from rough ER and transferred to the periplasmic region of the cell during an early stage of the floral bud. The other one is the lipid droplet, which reacts to polysaccharidic staining and is seen throughout floral bud development. The lipid droplets are closely associated with the Golgi bodies and seem to be dissolved in the vacuole. The materials found in the vacuoles appear to diffuse and pass through the cell walls as intercellular substances.

Hydroxyproline-containing diketopiperazines (HPCDs), including natural l-hydroxyprolyl-l-proline anhydride [cyclo(l-Hyp-l-Pro): D-104] and l-hydroxyprolyl-l-leucine anhydride [cyclo(l-Hyp-l-Leu): D-301], induce significant resistance in rice (Oryza sativa) against water stress caused by sodium chloride or mannitol, when the seeds are treated with the HPCDs during the initial four days of the germination period. The possibility that tricyclic HPCDs such as D-104 can be plant hormone candidates is discussed, based upon structure-activity relationships obtained by using D-104, D-301 and six derivatives thereof.

Flower formation of some Japanese pear cultivars, differing in the extent of apical dominance, was studied in relation to young-leaf removal (removing apical dominance) and in vitro vegetative apex culture.In all cultivars, removal of young leaves and disbudding promoted flowering in the remaining axillary buds on the long shoots as compared with only disbudding. The degree of promotion, however, remained within their flowering capacities, indicating that this capacity is inherent in the bud itself. Explants cultured in vitro formed flowers in the bract axils of their main shoot, regardless of whether they were prepared from the shoot apex or the axillary leaf bud. Occurrence of flowering in the explants was closely related to the flowering capacity characteristic of the cultivar from which they were derived. Flowering occurred predominantly in the explants with a particular range of node number, above or below which it decreased rapidly. The presence of gibberellin GA4+7 in the medium tended to decrease flowering of explants, but had no effect on their node number.

Effects of gibberellins GA3 and GA4 and of growth retardants succinic acid-2,2-dimethylhydrazide (B-9), (2-chlorethyl)trimethylammonium chloride (CCC) and (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-ol (S-3307) on flowering of Japanese pear cultivars ‘Kosui’ and ‘Chojuro’ were investigated. Explants were prepared from the shoot apex or the axillary bud.The presence of GA4 but not GA3 in the culture medium tended to decrease flowering of ‘Chojuro’ explants, although inhibition was less clear in ‘Kosui’ explants which showed low flowering percentages. S-3307 effectively promoted flowering, particularly for ‘Kosui’ explants. The promotive effect of CCC was slight or none, and B-9 reduced flowering. GA4 (but not GA3) or the growth retardants had a tendency to increase or decrease shoot and internode length of the explants; these morphological changes were not always associated with flowering behavior. The growth regulators had little or no effect on node number of the explants, which was closely related to flowering.Successive subculture of the vegetative apex in the adult form resulted in a rapid loss of flowering ability with an increase in shoot or internode length in the resulting explants, shifting to juvenile characteristics.

During screening of animal metabolites which induce drought resistance in plants, two diketopiperazines, cyclo(L-Hyp-L-Pro) (1) and cyclo(L-Hyp-L-Leu) (2), emerged as effective. When rice seeds were pretreated with the cyclic dipeptides (1 and2) during their germination period, the resulting seedlings showed significant resistance to water-stress caused by 0.5–1.5% NaCl solution or 2.5–5.0% mannitol solution.

Seasonal changes in lipid composition in the flavedo tissues of Naruto fruit were determined during August to early June.Total fatty acid content of phospho- and glycolipids, particularly that of glycolipids, decreased considerably with increased aging of the rind except during midwinter. In mid-winter that of neutral, phospho- and glycolipids showed a sharp peak, due largely to an increase in linoleic (18:2) acid in the first two and linolenic (18:3) acid in the last.Content of major phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE); and content of major glycolipids, mono-(MGDG) and di-galactosyl-diglyceride (DGDG), behaved in a way similar to that of phospho- and glycolipid total fatty acids, respectively. Seasonal variations in DGDG content were paralleled by, but greater than MGDG content. The PC/PE ratio decreased steadily from August to December and thereafter remained unchanged. Free sterol content decreased from August to October and thereafter changed little except for showing a peak in mid-winter. However, the sterol/phospholipid ratio was relatively constant during winter. The sitosterol/stigmasterol ratio more than doubled in the maturing period (December-June) compared with that in the growing period (August October).