Investigating several environmental factors affecting plant growth implies having sound experimental facilities equipped to test individual factors in lab-scale although applicable later at the industrial scale. Sometimes, detailed information is hardly given in a manuscript that allows for replications by other authors, maybe due to the shortening of pages requested by journal publishers and editors. A system and methodology was developed for qualitative and quantitative analyses of baby leaf vegetables (BLV) raised in floating growing systems (FGS). Lab-scale pilot plants (LSPP) were developed in 2 greenhouses differing in structure and equipment, suitable for different growing seasons in a continental climate. The equipment and technology allowed multiple treatments and replicates for sound statistical design and data analyses. Environmental conditions and cultural techniques were studied in major and minor species (white mustard, Brassica alba L. Boiss; black mustard, Brassica nigra L. Koch; garden cress, Lepidium sativum L.; water cress, Nasturtium officinale R. Br.; rocket salad, Eruca sativa Mill.; perennial wild rocket, Diplotaxis tenuifolia L. DC.; corn salad, Valerianella olitoria L.; baby spinach, Spinacia oleracea L.) to determine best cultivation techniques in a standard soilless culture system (SCS) for BLV, based on FGS. Considering that SCS can improve raw material quality at harvest, and enhance the postharvest shelf-life of many vegetables and herbs, a standardized growing system is required to obtain premium quality raw material in terms of commercial stage, low nitrate content and long shelf-life. Among the SCS used, the FGS are suitable systems to grow leafy vegetables because the plants can grow at high densities, thereby producing high yields, and in a short time. FGS are based on sub-irrigation technology, avoiding over-head irrigation and contact between nutrient solution and edible parts, and result in greater qualitative and quantitative yields than the traditional cultivation techniques, reducing pollution, crop and substrate residues, leading to clean raw material with potential low microbiological load. The FGS is a modern technology that could be exploited more to enhance yield, quality and safety of fresh and fresh-cut BLV. The LSPP installed are providing the basis for expanding the research to other species and agronomic factors.
The genus Actinidia includes widely-sold kiwifruit, and is thus horticulturally important. We investigated the distribution, ploidy levels, and fruit characteristics of the natural populations of three edible Actinidia species [Actinidia arguta (Siebold & Zucc.) Planch. ex Miq., Actinidia kolomikta (Maxim. & Rupr.) Maxim., and Actinidia polygama (Siebold & Zucc.) Planch. ex Maxim.] in Hokkaido, the northern island of Japan. Actinidia arguta and A. kolomikta were common, and their habitat ranges overlapped. Actinidia polygama was less common, and its habitat was mostly limited to lowland deciduous forests. Flow cytometric analysis revealed that all wild collections of A. kolomikta and A. polygama were diploid, and that A. arguta was tetraploid, suggesting a lack of intraspecific ploidy variation. Fruit shape varied from round to ovoid in A. arguta, ranged from ovoid to ellipsoidal in A. kolomikta, and was ellipsoidal in A. polygama. The fruit skin of all species was glabrous, and skin color was orange in A. polygama, green to dark green in A. kolomikta, and light to dark green in A. arguta. The fresh weight of A. kolomikta fruit was less than that of A. arguta, and the soluble solids content (SSC) of the fruits varied widely within species. One sample of A. arguta had extremely high SSC (average Brix of 30.8%). The ascorbic acid content (AAC) was the highest in A. kolomikta (up to 805 mg per 100 g fresh weight). Actinidia arguta and A. kolomikta germplasm may be useful for breeding new kiwifruit varieties for cultivation in cold-temperate regions.
Kumquats (Fortunella spp.) is classified into the subfamily Aurantioideae (family Rutaceae). The taxonomy and phylogeny of this genus are complicated and controversial. Therefore, we carried out a estimation based on chromomycin A3 (CMA) karyotype composition in order to understand the cytogenetics and evolution of the genus Fortunella. Among the 6 Fortunella species examined, Fortunella hindsii var. chintou Swing. (Hongkong kumquat) showed the simplest CMA karyotype composition. On the other hand, close relationships were found among the 3 species F. margarita (Lour.) Swing. (Oval kumquat), F. japonica (Thunb.) Swing. (Round kumquat), F. crassifolia Swing. (Meiwa kumquat). Fortunella polyandra (Ridl.) Tan. (Malayan kumquat) and F. obovata hort. ex Tan. (Changshou kumquat) had type E chromosomes, which is an elemental chromosome type for Citrus. We concluded that there are only two true species for the genus Fortunella, F. hindsii and F. margarita complex, which includes F. margarita, F. japonica, and F. crassifolia, and that F. polyandra and F. obovata should be classified as natural or horticultural hybrids.
Shift in locations suitable for loquat [Eriobotrya japonica (Thunb.) Lindl.] due to global warming leads to a high requirement for accurate assessment of suitable locations. This study aimed to develop a technique for using past winter air temperatures to judge whether an area is suitable for loquat production. The relationship between air temperatures and cold damage levels observed in orchards of four main production areas (Chiba, Kagawa, Nagasaki, and Kagoshima prefectures) for some years were analyzed. The survival rates of young fruit of each variety were positively correlated with the annual minimum air temperature. Threshold air temperatures for cold damage (the air temperature at which the survival rate decreased to 80%) of six varieties (‘Tanaka’, ‘Mogi’, ‘Natsutayori’, ‘Nagasakiwase’, ‘Harutayori’, and ‘Biwa Nagasaki No. 21’) were acquired by using statistically significant linear regressions. ‘Tanaka’ had excellent cold hardiness, with the lowest threshold air temperature, whereas ‘Nagasakiwase’ and ‘Harutayori’ tolerated the cold less well, with higher threshold air temperatures. Locations suitable for production of ‘Tanaka’ and ‘Nagasakiwase’ were judged based on the upper limit of the threshold air temperature for cold damage. The current production areas agreed with the locations judged to be suitable for the production of each variety. These results suggest that the threshold air temperatures for cold damage obtained in the present study provide a valid assessment of suitable current and future locations for both varieties.
Satsuma mandarin (Citrus unshiu Marc.) has two GA 20-oxidase genes, CuGA20ox1 and CuGA20ox2, and the genomic sequence for CuGA20ox1 is shorter than that for CuGA20ox2, although the coding region of cDNA for CuGA20ox1 is slightly longer than that for CuGA20ox2. Southern blot analysis revealed that 12 Citrus cultivars examined and trifoliate orange [Poncirus trifoliata (L.) Raf.] have at least two types of GA 20-oxidase genes, such as CuGA20ox1 and CuGA20ox2 genes. CuGA20ox1 and CuGA20ox2 were differentially expressed in various tissues. CuGA20ox1 was expressed in almost all of the tissues investigated with relatively higher expression in vegetative than in reproductive tissues, whereas CuGA20ox2 was specifically expressed in flower buds just before anthesis. These distinct expression patterns of CuGA20ox1 and CuGA20ox2 imply that function of these two genes diverged in the process of evolution. The specific and relatively higher expression of CuGA20ox2 in flower buds would explain why GA-like activity was higher in Satsuma mandarin’s ovaries at anthesis. Transgenic Arabidopsis [Arabidopsis thaliana (L.) Heynh] plants ectopically expressing CuGA20ox1 or CuGA20ox2 were examined to elucidate the function of these two Satsuma mandarin genes. Phenotypic analysis revealed that both CuGA20ox1 and CuGA20ox2 caused elongated inflorescence but did not affect the timing of flowering in transgenic Arabidopsis as compared with wild-type controls. Ectopic expression of CuGA20ox1 and CuGA20ox2 significantly affected the levels of GA24 and GA34 on the non-13-hydroxylation pathway; GA24 decreased and GA34 increased. This observation indicates that both CuGA20ox1 and CuGA20ox2 accelerated the conversion of GA24, a substrate of a GA 20-oxidase, to GA9, a precursor of an active form of GA4. Likewise, on the early-13-hydroxylation pathway, ectopic expression of CuGA20ox1 significantly decreased GA19 and increased GA29 and GA8, inactive metabolites of 2-hydroxylation of GA20 and GA1, respectively, suggesting the activation of this biosynthetic pathway. CuGA20ox2 also had a tendency to activate the early-13-hydroxylation pathway although it increased only GA20 with a statistically significant difference. Taken together, we concluded that CuGA20ox1 and/or CuGA20ox2 activated both the early-13- and non-13-hydroxylation pathways for increasing active GAs, resulting in elongated inflorescences in transgenic Arabidopsis.
A red-fleshed peach (Prunus persica L. Batsch ‘Tenshin Suimitsuto’; ‘Tianjinshuimi’ in Chinese) was used to study the mechanisms of skin and flesh pigmentation. Anthocyanin accumulation was detected at the pre-endocarp-hardening and maturation stages in skin, while it appeared from maturation stage in flesh. The flesh at harvest stage contained approximately 1.1 mg·g−1 FW of anthocyanin. In contrast, flavonoid and phenolic compounds were found in all stages. The final phenolics concentration was 1.6 mg·g−1 FW. To study the effects of light, fruits were on-tree bagged in double-layered paper bags. The total anthocyanin content in the skin was significantly lowered by bagging, but not in the flesh. This suggested that flesh tissue pigmentation was less sensitive to light intensity than that of skin tissue, and thus, anthocyanin accumulation in flesh occurred even under low light conditions. Dark treatments, such as triple-layered paper bagging, significantly reduced anthocyanin and phenolic concentrations in the skin and flesh. A combined treatment of darkness and an auxin polar transport inhibitor, 2,3,5-triiodobenzoic acid (TIBA), had no effect on anthocyanin concentration in skin and flesh. However, total flavonoids in the skin was increased by TIBA treatments under darkness. Factors affecting anthocyanin accumulation in the flesh tissue are discussed.
The aim of this work was to study the effect of substrate disinfection and application of plant growth-promoting rhizobacteria (Bacillus subtilis) on the yield, quality and safety of watercress grown in a floating system. Substrate disinfection had a positive effect on plant development because it increased the shoot antioxidant capacity and general plant growth and decreased the colony-forming units of molds. In turn, inoculation with B. subtilis increased the antioxidant capacity but decreased the chlorophyll a, chlorophyll b, and carotenoid contents and did not affect the rest of the parameters measured. In conclusion, our results showed that the effects of substrate disinfection were more pronounced than those obtained by B. subtilis inoculation, suggesting that it would be more convenient to reserve the use of plant growth-promoting rhizobacteria for other conditions, such as abiotic stress.
We investigated morphological changes in petal cells during flower development and opening in Eustoma grandiflorum. The morphology of petal epidermal cells was observed by scanning electron microscopy, and their number was determined. The numbers of adaxial and abaxial epidermal cells increased during flower development. Increase in these numbers terminated before flower opening earlier in abaxial than in adaxial epidermal cells. Measurements of cell number and area showed that the petal growing stage during flower development and opening can be divided into four phases: cell division and expansion, cell division, cell division and expansion, and cell expansion. Adaxial epidermal cells in the petal blade showed a conical-papillate shape whereas adaxial epidermal cells in the petal claw were longitudinally elongated in shape. Abaxial epidermal cells were longitudinally elongated in both petal blade and claw. The ultrastructure of petal cells at the bud stage and the open stage was observed by transmission electron microscopy. In the petal cells at the bud stage, nuclei and several plastids were observed, although the cells were mainly occupied with vacuoles. Relatively large spherical electron-dense bodies were observed only in the vacuoles of adaxial epidermal cells at the bud stage. The petal cells were largely occupied with enlarged vacuoles at the open stage. We conclude that petal growth in Eustoma is divided into four phases, based on the activities of cell division and expansion, and that petal growth in the final phase is mainly due to cell expansion with marked enlargement of vacuoles.
An unidentified compound was detected in sweet pea (Lathyrus odoratus L. ʻDianaʼ) petals by HPLC analysis using a cation-exchange column for soluble carbohydrate analysis. This compound was identified as 2-cyanoethyl-isoxazolin-5-one (2-CEIX) using 1H-NMR, 13C-NMR, and CI-MS and ESIMS. 2-CEIX was detected in the petals, leaves and stem. Amino acid and other nitrogenous compound contents in these organs were compared with 2-CEIX. The content of asparagine was highest, followed by 2-CEIX in the petals, and 2-CEIX was highest among nitrogenous compounds in the stem and leaves. The 2-CEIX content in the petal decreased during flower opening, but those in the petals and the other floral parts increased during senescence regardless of sucrose treatment. These trends differed from those of monosaccharides, sucrose and cyclitols. Thus, the role of 2-CEIX appears to differ from those of soluble carbohydrates. 2-CEIX was not detected in phloem and xylem saps. The results suggest that 2-CEIX is a major nitrogenous compound of low molecular weight and is likely to be produced in situ in various organs in sweet pea.
The effect of gibberellin (GA) on chilling-induced stem elongation and flowering in Lavandula × intermedia was investigated using several GAs and GA biosynthesis inhibitors related to chilling temperature and its period. Identification of GA1, GA19, GA20, and GA53 as endogenous GAs by GC/MS suggests the early C-13 hydroxylation pathway (→GA53→GA44→GA19→GA20→GA1→) is functioning, and GA1 is the biologically active GA in L. × intermedia. GA3 increased stem elongation with or without chilling treatment (CT), but did not induce flowering without CT. There was little difference in the effects on stem elongation and flowering among GA1, GA3, GA5, and dimethyl-GA4. GA biosynthesis inhibitor, especially uniconazole-P, inhibited stem elongation and flowering, but the inhibition was abolished by GA3. At least several weeks of CT were necessary for flowering, for example, in 8-week CT at 5°C, 9-week CT at 6°C and 12-week CT at 7°C. This period was defined as the minimum CT period. Under the minimum CT period, GA3 enhanced the flowering. However, the effect on flowering by GA3 was not found when the CT period became longer, for example, in 12-week CT at 5°C, 12-week CT at 6°C and 15-week CT at 7°C. This longer period was defined as the maximum CT period. These results suggest that the expression of endogenous GA is necessary for flowering in L. × intermedia, that the florigenic effect of GA3 on flowering varies with the period of CT, and that GA3 enhances the effect of CT on flowering in L. × intermedia, but cannot replace CT.
Bicolor flowering dahlias generally produce inflorescences with bicolor petals characterized by a colored basal part and a white tip; however, they frequently produce single-colored petals. This petal color lability prevents uniform production of cut or pot flowers of bicolor dahlias and reduces the economic value of bicolor cultivars. In this study, to reveal the underlying mechanism and control color lability, the pattern of occurrence of single-colored petals was characterized in a red–white bicolor flowering cultivar ‘Yuino’. ‘Yuino’ produced inflorescences with bicolor petals, red petals, and both red and bicolor petals. Red petals occurred almost always at the outer whorls or sectorally in a mixed inflorescence, similar to a chimera or a lateral mutant. The occurrence of red petals was higher in field experiments during May to December than in greenhouse experiments during October to next July. We identified the “R-line” plant, which produced red petals with high frequency during the winter to spring cultivation; this characteristic to produce red petals with high frequency was retained through vegetative propagation. There were strong relationships between inflorescence color and leaf phenotype; red petal-producing plants accumulated flavonoids in leaves, whereas only bicolor petal-producing plants tended not to accumulate flavonoid in leaves. This suggests that petal color of ‘Yuino’ is associated with flavonoid synthetic potential in shoot. Therefore, a phenotypic difference is observed not only in petal colors but also at the whole plant level.