Camellia flowers are highly prized for their beauty worldwide and are strongly symbolic in many cultures. A new interspecific hybrid cultivar, Camellia ‘Maozi’, generated by crossing Camellia pubipetala with C. japonica ‘Dahong Mudan’, exhibits strong hybrid vigor and has small flowers with a rare light tone of purple. In southwest China with a subtropical monsoon climate, young Camellia ‘Maozi’ trees flush shoots three times in spring, summer, and autumn, with an average annual growth of 12.9 cm. Adult trees flush once a year. Floral bud formation occurs in late April and early May. Camellia ‘Maozi’ flowers are sterile with no fruits and seeds produced. While an individual flower wilts 4–8 days after opening, the blossom can last 1–3 months. Frost damage can be found in young leaves when temperature drops to 4–7 °C. Under direct sunlight with temperatures of 37–39 °C lasting for more than 2 days, young leaves can turn yellow on their edges. Its primary diseases include sooty mold, shoot tip blight, and peony leaf tip blight. Its primary insect pests are tea green leafhopper (Jacobiasca formosana) and tea aphid (Toxoptera aurantii). Rooting of stem cuttings occurs directly from stems, mostly without callus development. Two hours of treatment with 500 mg·L−1 indole-3-butyric acid and rooting in a mix of latosolic red soil and vermiculite (2:1 v/v) resulted in high rooting rate and quality of aboveground growth. Grafting can be carried out from May to September, while survival rate and new shoot length are highest in July. The most compatible rootstock is C. oleifera, followed by C. polyodonta. The results of this study are of value for understanding the reproductive biology of Camellia ‘Maozi’ and further disseminating it as a new cultivar for camellia collection.
Xiao-Juan Wei, Xiao-Jing Liang, Jin-Lin Ma, Kai-Xiang Li, and Haiying Liang
Hongli Wei, Chao Gao, Jie Qiu, Zhiyan Guo, Biao Wang, and Li Long
Camellia weiningensis is a typical woody edible oil tree species in the northwest alpine area of Guizhou Province, China, but its embryological development is not fully elucidated. Here, we assessed flower bud differentiation, microsporogenesis, and male-female gametophyte development in this species. We performed cytological observations of flower bud development in C. weiningensis through conventional paraffin sectioning, scanning electron microscopy, and stereomicroscopy to establish the corresponding relationships between the external morphology and internal structure. The flowers were hermaphroditic and exhibited a short flower bud differentiation time. Although pistil development occurred later than stamen development, both organs matured synchronously before flowering. The anther contained four sacs that exhibited a butterfly shape in transverse sections. The anther wall comprised the epidermis, anther chamber inner wall, two middle layers, and a glandular tapetum (from outside to inside). Microspore mother cells formed a tetrahedral tetrad through meiosis, mature pollen was two-celled with three germination pores, and the ovary comprised three to five chambers (three chambers predominated). Multiple ovules were invertedly attached to the axial placentation and exhibited double integuments and a thin nucellus. The embryo sac exhibited Allium-type development, and the mature embryo sac was seven-celled and eight-nucleated. In C. weiningensis, embryonic development does not exhibit abnormalities, and stamen development occurs earlier than pistil development. During flower bud development, the inner development process of male and female cells can be judged according to their external morphological characteristics. Our results may provide a theoretical basis for regulating flowering in and the cross-breeding of C. weiningensis.
Tong Zhang, Yingjie Yan, Chuantong Li, Junmei Liu, Dongxue Yin, Xiangying Xiong, Wei Liu, and Yueqin Yang
This study investigated the effects of illumination time and soil moisture on seed germination and seedling establishment of Magnolia sprengeri Pamp. to improve the seed germination percentage and seedling survival percentage of M. sprengeri. It is of great significance for rapid propagation, seedling regeneration, field management, and artificial high-efficiency cultivation of M. sprengeri. In this study, the seeds of natural M. sprengeri populations from original habitat were used as test materials. Seed germination and seedling establishment of M. sprengeri were performed under different illumination time and soil moisture treatments in artificial climate incubator. The study found that there were significant differences among various key parameters related to seed germination and seedling establishment under different treatments (P < 0.05). Germination percentage, germination potential, germination index, vigor index, germination rate, plant height, number of leaves, base diameter, taproot length, number of lateral roots, maximum lateral root length, single plant leaf area, fresh weight, and seedling survival rate reached the maximum at continuous illumination and 13% of soil moisture, respectively. By the integrative evaluation for the influence of these two factors on seed germination and seedling establishment, soil moisture is a dominant factor affecting seed germination and seedling establishment, whereas illumination is an important promoting factor for seedling establishment of M. sprengeri. Continuous illumination and 13% of soil moisture content is suitable for seed germination and seedling establishment of M. sprengeri.
Chunlian Jin, Dan Sun, Chang Wei, Zhenhua Guo, Chunmei Yang, and Fan Li
Gypsophila paniculata is an ornamental crop with medicinal value. To date, limited information has been reported about the natural products in G. paniculata to explain its medicinal function. The current study reports the natural products found in G. paniculata stem for the first time. Thirty-three compounds were isolated from the extract of G. paniculata stem and identified by gas chromatography-mass spectrometry, 10 of which have contents >2%. These were 2-O-methyl-D-mannopyranose (37.4706%), glycerol (12.5669%), two tetratetracontane isomer (7.6523 + 3.5145%), tetrahygro-4-pyranol (5.3254%), 1,6-anhydro-beta-d-glucopyranos (4.7507%), palmitic acid (4.1848%), 4-hydroxy-3-methoxystyrene (3.7439%), methyl-octadeca-9,12-dienoate (2.7490%), and 2-deoxy-D-galactose (2.6193%). Another bioactive compound, condrillasterol, was identified with 1.3384% content. We also reported that G. paniculata possesses antioxidant activity possibly associated with the presence of a phenolic chemical 4-hydroxy-3-methoxystyrene. Our data collectively demonstrate that G. paniculata contains some bioactive compounds with high contents and antioxidants, consistent with its role as a medicinal herb.
Wei Li, Rongcai Yuan, Jacqueline K. Burns, L.W. Timmer, and Kuang-Ren Chung
Colletotrichum acutatum J. H. Simmonds infects citrus flower petals, causing brownish lesions, young fruit drop, production of persistent calyces, and leaf distortion. This suggests that hormones may be involved in symptom development. To identify the types of hormones, cDNA clones encoding proteins related to ethylene and jasmonate (JA) biosynthesis, indole-3-acetic acid (IAA) regulation, cell-wall modification, signal transduction, or fruit ripening were used to examine differential gene expressions in calamondin (Citrus madurensis Lour) and/or `Valencia' sweet orange (Citrus sinensis Osbeck) after C. acutatum infection. Northern-blot analyses revealed that the genes encoding 1-aminocyclopropane-1-carboxylate (ACC) oxidase and 12-oxophytodienoate required for ethylene and JA biosynthesis, respectively, were highly up-regulated in both citrus species. Both gene transcripts increased markedly in petals, young fruit and stigmas, but not in calyces. The transcripts of the genes encoding IAA glucose transferase and auxin-responsive GH3-like protein, but not IAA amino acid hydrolyase, also markedly increased in both species 5 days after inoculation. The expansin and chitinase genes were slightly up-regulated, whereas the senescence-induced nuclease and ß-galactosidase genes were down-regulated in calamondin. No differential expression of transcripts was detected for the genes encoding expansin, polygalacturonase, and serine-threonine kinase in sweet orange. As compared to the water controls, infection of C. acutatum increased ethylene and IAA levels by 3- and 140-fold. In contrast, abscisic acid (ABA) levels were not significantly changed. Collectively, the results indicate that infection by C. acutatum of citrus flowers triggered differential gene expressions, mainly associated with IAA, ethylene, and JA production and regulation, and increased hormone concentrations, consistent with the hypothesis of the involvement of phytohormones in postbloom fruit drop.
Gaofeng Zhou, Bixian Li, Jianmei Chen, Fengxian Yao, Guan Guan, Guidong Liu, and Qingjiang Wei
Soil acidification and boron (B) starvation are two dominant abiotic stress factors impacting citrus production in the red soil region of southern China. To evaluate the combined effects of low pH and B deficiency on plant growth, gas exchange parameters, and the concentrations of B and other mineral nutrients, ‘HB’ pummelo seedlings were treated under B deficiency (0 μM H3BO3) or adequate B (23 μM H3BO3) conditions at various low pH levels (4.0, 5.0, and 6.0). The seedlings were grown with modified half-strength Hoagland’s solution under greenhouse conditions for 12 weeks. Plant biomass, leaf area, seedling height, and root traits were remarkably inhibited by low pH and B deficiency stresses, and these parameters were extremely reduced with the decrease in pH levels. After 12 weeks of treatment, typical stress symptoms associated with B deficiency in citrus leaf were observed, with more severe symptoms observed at pH 4.0 and 5.0 than at pH 6.0. Leaf gas exchange parameter measurements showed that leaf photosynthesis was significantly inhibited under both low pH and B-deficient conditions. Notably, the lower the pH level, the greater the inhibition under both normal and deficient B conditions. Further investigations of the mineral nutrient concentrations showed that under both low pH and B deficiency, the concentrations of B and other mineral nutrients were influenced remarkably, particularly at pH 4.0 and 5.0. The physiological and nutritional results of the ‘HB’ pummelo seedlings indicated that low pH can exacerbate the effects of B deficiency to a certain extent.
Xiao-Juan Wei, Jinlin Ma, Kai-Xiang Li, Xiao-Jing Liang, and Haiying Liang
The flowers of Camellia chrysantha, commonly named as golden camellia, are treasured for their unique yellow color and are popularly used for tea. Compared with common camellia flowers that are either red, purple, pink, or white, golden camellia flowers are rare and are in high market demand. Our study was aimed to induce flowering in juvenile C. chrysantha grafted plants with urea and paclobutrazol (PBZ), a growth retardant. Generally, it takes 6–8 years for C. chrysantha seedlings and 5–6 years for grafted plants to set flower buds. With a 4 × 4 factorial design, four dosages of urea (1, 3, 5, or 8 g/plant) and four concentrations of PBZ (50, 150, 350, and 750 ppm) were tested on 4-year-old C. chrysantha grafted plants. Significant interaction between urea and PBZ was observed, and nine of the 16 combinations produced significantly more flower buds than the control, although not all flower buds could open because of abscission. High concentrations of PBZ and high dosages of urea were generally associated with severe defoliation and slow growth of basal stem diameter. When taking bud abscission into account, combinations of 150 ppm PBZ with 1 g urea and 350 ppm PBZ with 3 g urea resulted in significant flowering in juvenile C. chrysantha grafted plants without negative effects on vegetative growth and flower bud size and severe defoliation. This is the first report on flowering induction in a golden camellia species using juvenile plants. Our results suggest that application of optimized PBZ and urea doses can be a potential means for manipulation of early flowering in golden camellia species.
Hongli Wei, Chao Gao, Jie Qiu, Li Long, Biao Wang, Lu Yang, and Yang Hu
This study aimed to investigate the flowering biological characteristics, floral organ characteristics, and pollen morphology of Camellia weiningensis Y.K. Li. These features of adult C. weiningensis plants were observed via light microscopy and scanning electron microscopy (SEM). Pollen viability and stigma receptivity were detected using 2,3,5-triphenyltetrazole chloride (TTC) staining and the benzidine–hydrogen peroxide reaction method. C. weiningensis is monoecious, with alternate leaves and glabrous branchlets. Its flowering period lasts 2 to 4 months, and the flowering time of individual plants lasts ≈50 days, with the peak flowering period from the end of February to the middle of March. It is a “centralized flowering” plant that attracts a large number of pollinators. Individual flowers are open for 12 to 13 days, mostly between 1230 and 1630 hr, and include four to six sepals, six to eight petals, ≈106 stamens, an outer ring of ≈24.6-mm-long stamens, an inner ring of ≈13.4-mm-long stamens, one pistil, and nine to 12 ovules. The flowers are light pink. The style is two- to three-lobed and 16.6 mm long, showing a curly “Y” shape. The contact surface of the style is covered with papillary cells and displays abundant secretory fluid and a full shape, facilitating pollen adhesion. The pollen is rhombohedral cone-shaped, and there are germ pores (tremoids). The groove of the germ pore is slender and extends to the two poles (nearly reaching the two poles). The pollen is spherical in equatorial view and trilobate in polar view. The pollen vitality was highest at the full flowering stage, and the stigma receptivity was greatest on days 2 to 3 of flowering. The best concentration of sucrose medium for pollen germination was 100 g/L. The number of pollen grains per anther was ≈2173, and the pollen-to-ovule ratio was 23,034:1. C. weiningensis is cross-pollinated. Seventy-two hours after cross-pollination, the pollen tube reached the base, and a small part entered the ovary. The time when the pollen tube reached the base after pollination was later than that in commonly grown Camellia oleifera. The results of this study might lay an important foundation for the flowering management, pollination time selection, and cross-breeding of C. weiningensis.
Zhigang Ouyang, Huihui Duan, Lanfang Mi, Wei Hu, Jianmei Chen, Xingtao Li, and Balian Zhong
In eukaryotic systems, messenger RNA regulations, including splicing, 3′-end formation, editing, localization, and translation, are achieved by different RNA-binding proteins and noncoding RNAs. The YTH domain is a newly identified RNA-binding domain that was identified by comparing its sequence with that of splicing factor YT521-B. Previous study showed that the YTH gene plays an important role in plant resistance to abiotic and biotic stress. In this study, 211 YTH genes were identified in 26 species that represent four major plant lineages. Phylogenetic analysis revealed that these genes could be divided into eight subgroups. All of the YTH genes contain a YT521 domain and have different structures. Ten YTH genes were identified in navel orange (Citrus sinensis). The expression profiles of these CitYTH genes were analyzed in different tissues and at different fruit developmental stages, and CitYTH genes displayed distinct expression patterns under heat, cold, salt, and drought stress. Furthermore, expression of the CitYTH genes in response to exogenous hormones was measured. Nuclear localization was also confirmed for five of the proteins encoded by these genes after transient expression in Nicotiana benthamiana cells. This study provides valuable information on the role of CitYTHs in the signaling pathways involved in environmental stress responses in Citrus.