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  • Author or Editor: Li Chang x
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Experiments were conducted on 6-month-old chinese ixora (Ixora chinensis Lam.) from February 1999 to April 2000. Floral development was studied with scanning electron microscopy (SEM) to determine the flowering sequences. Morphological characters were used to clarify the stages of flowering processes. The time of organogenesis and flowering arrangement was established through field observations. Floral evocation occurred in early September, floral initiation occurred in the middle of September and floral differentiation began in late September. A distinctly convex apex with bracts around the shoulder indicated the beginning of reproductive development. Subsequently, primary inflorescence axes were observed and differentiated into secondary, tertiary, and quaternary inflorescence axes consecutively in about one and a half months. Once the terminal apex reached the inflorescence bud stage, it would flower without abortion, and this may be assessed as no return. The sepals, petals, stamens, and pistil were well developed thereafter and anthesis was achieved in January through March in the following year. The observation of floral differentiation sequences and investigation of floret arrangement made it certain that chinese ixora had cymose inflorescence (cyme), but not corymb. A quadratic equation was established to predict floret number from the differentiation level (a quantitative description of differentiation stage) of a developed inflorescence.

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The flowering control of Oncidesa Gower Ramsey ‘Honey Angel’ is important and in-demand by the industry. Therefore, an understanding of the development of inflorescence and vegetative shoot from the leaf axils on the current shoot is required. The internode of a young Oncidesa current shoot between the 0th (at the base of the pseudobulb) and 1st (immediately above the pseudobulb) nodes can enlarge to form a pseudobulb, and the axillary bud on the 0th or -1st (immediately below the 0th node) node can differentiate into an inflorescence bud. The axillary buds on the lower nodes (-2nd to -4th nodes) can remain vegetative. In this study, we investigated the growth and anatomical features of axillary buds at various stages during the growth of the current shoot. We sampled the axillary buds on the 0th to -4th nodes from the current shoots when they were 10, 15, 20, 25, and 30 cm in length for sectioning and anatomical observations. Vegetative buds on the -2nd to -4th nodes grew faster and had more nodes than the inflorescence bud when the current shoot grew from 10 to 25 cm. However, when the current shoot elongated from 25 to 30 cm, the length and node number in the inflorescence bud on the 0th node increased and the inflorescence branch primordia were observable. The length and node number of the inflorescence bud became the same as that of the vegetative buds, which had no further growth, whereas the current shoot grew from 25 to 30 cm. The pseudobulb began to emerge from the leaf sheath (unsheathing) when the current shoot had reached 30 cm in length. Therefore, the time when the pseudobulb started to unsheathe from its subtending leaf was critical for the reproductive growth of Oncidesa Gower Ramsey ‘Honey Angel’ when growth acceleration of the inflorescence bud occurred. Evaluating the current shoot length can be a nondestructive method of estimating the developmental stage of the inflorescence bud.

Open Access

Partridge tea is one of the famous local herbal teas of Hainan Island, China. In the present study, headspace solid-phase microextraction and gas chromatography-mass spectrometry were combined to determine and analyze the volatile components in the red and green leaves of partridge tea. Seventeen volatile components were identified in the red young leaves. The olefins, alkanes, and alcohols accounted for 71.24%, 1.1%, and 0.54%, among which the main components were caryophyllene (22.50%), humulene (18.73%), and α-guaiene (8.78%), respectively. Twenty volatile components were identified from red mature leaves, including 34.74% olefins, 6.14% esters, and 3.11% acids. Eighteen volatile components were identified from green young leaves, among which olefins (70.52%), alkanes (4.32%), and alcohol (0.89%) were the major components. Nineteen volatile components were identified from green mature leaves, among which the olefins, esters, and acids were the major components with the contents of 46.04%, 6.38%, and 1.37%, respectively. Results showed that the major volatile components of partridge tea were olefins, in which caryophyllene was the most abundant. The contents of volatile components between red leaves and green leaves had notable differences, which might be useful for germplasm identification of partridge tea.

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In this study, the effects of light-emitting diode (LED) panels with different illumination schedules and mounted above butterhead lettuce (Lactuca sativa var. capitata) seedlings on lettuce growth and photosynthesis were examined, and the performance of the vertical and horizontal movable system on energy savings was evaluated. The illumination schedules used were fixed LED [F-LED (four LED panels illuminated the area below)] and movable LED [M-LED (two LED panels moved left and right once per day to illuminate the same area as F-LED)] at distances of 10 and 30 cm above the seedlings. The plant yields were uniform in all LED treatments. The highest light utilization efficiencies and lowest electricity consumption were found for the treatments with irradiation from a shorter distance above the seedlings. The true leaf numbers and ascorbic acid concentrations were the highest in the M-LED and F-LED treatments at a distance above the seedlings of 10 cm, while the leaf lengths and sucrose concentrations in these groups were significantly lower than those in the 30-cm treatment. These results indicate that illumination with M-LED can halve the initial light source input while maintaining yield and that sustained illumination from a shorter distance above the seedlings is the main factor in electricity savings.

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Soluble acid invertase [SAI (Enzyme Commission 3.2.1.26)] plays an important role in catalyzing the hydrolysis of sucrose into hexoses and regulates floral development. Full-length cDNAs encoding RhSAI1 and RhSAI2 isoforms were cloned from Rhododendron hybrid ‘Yuqilin’ and they exhibited high amino acid sequence identity (89%) to each other. The protein sequences contain highly conserved motifs present in all SAIs, including the β-fructosidase motif N-D-P-(D/N), a putative active site W-E-C-(I/V)-D, and R-D-P. The expression of RhSAI1 and RhSAI2 genes was under spatial and temporal control. Expression of both RhSAI1 and RhSAI2 genes was most abundant in stems, and expression was lowest in roots and leaves, respectively. The expression of RhSAI2 was significantly lower than that of RhSAI1 in all organs. During floral development, RhSAI1 was highly expressed at the earliest stage (Stage I), decreased until Stage III, and increased again at the terminal stage. The pattern of RhSAI2 expression was distinctly different, showing a continuous increase during floral development. Consistent with the levels of RhSAI1 expression, SAI activity decreased during floral development and was inversely correlated with the soluble sugar content. Abundant expression of RhSAI1 at the transcriptional level in addition to high SAI activity during the initial stages of floral development may play a vital role in supplying the energy needed for rapid cell division and growth of flowers.

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Rhododendron delavayi Franch. is an important ornamental plant and often plays a role in natural hybridization with other sympatric species in Rhododendron subgenus Hymenanthes. Fifteen microsatellite loci were developed and characterized in this species. The average allele number of these microsatellites was four per locus, ranging from three to six. The ranges of expected (HE ) and observed (HO ) heterozygosities were 0.0365 to 0.7091 and 0.0263 to 0.9512, respectively. Cross-species amplification in R. agastum and R. decorum showed that a subset of these markers holds promise for congeneric species study. These sets of markers are potentially useful to investigate the genetic structure and gene flow of R. delavayi and other congeneric species.

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Light, as the energy and signal sources for plant growth and development, is one of the most important environment factors in recently developed plant factories with artificial light (PFALs). To find the optimal combination of light wavelengths for lettuce (Lactuca sativa cv. ‘Tiberius’) plant growth in a PFAL, four treatments, each using red (R; 662 nm) and blue light (B; 447 nm) with a ratio of 4:1 and photon flux density (PFD) of 150 μmol·m−2·s−1, and mixing, respectively, with 50 μmol·m−2·s−1 of green light (G; 525 nm; RBG), yellow light (Y; 592 nm; RBY), orange light (O; 605 nm; RBO) and far-red light (FR; 742 nm; RBFR), were set up during this experiment. A combination of R and B with a ratio of 4:1 and PFD of 200 μmol·m−2·s−1 was set as the control (RB). The responses of lettuce growth, morphology, anatomical structure of the lettuce leaf, photosynthetic performance, lettuce nutritional quality, and energy use efficiency were investigated. The results showed that RBG, RBO, and RBFR increased the shoot fresh weight of lettuce by 20.5%, 19.6%, and 40.4%, and they increased the shoot dry weight of lettuce by 24.2%, 13.4%, and 45.2%, respectively, compared with those under RB. The Pn under RBY was significantly lower than that under RB, although no significant differences in chlorophyll or carotenoid content were found between RBY and RB. RBG increased the lettuce leaf area, the thickness of the leaf palisade tissue, Pn, and light use efficiency compared with those under RB. Plants grown under RBO showed better photosynthetic capacity, such as higher Pn, ΦPSII, and other photosynthetic parameters. RBFR caused an increase in lettuce leaf area and energy use efficiency, but a decrease in leaf thickness and Pn of the single leaf. Moreover, tipburn injury was observed under RBFR. Therefore, these results demonstrate that RBG and RBO can be considered optimal combinations of light wavelengths for lettuce growth in a PFAL in this experiment, although plant growth can also be improved by using RBFR.

Open Access

To compare the effects of various zinc (Zn) foliar fertilizers on correcting citrus Zn deficiency and to explore an effective correcting method, three common Zn fertilizers, Zn sulfate heptahydrate (ZnSO4.7H2O), Zn chloride (ZnCl2), and Zn nitrate hexahydrate [Zn(NO3)2.6H2O], were selected to spray the Zn-deficient citrus leaves, tested at different concentrations, with or without organosilicone surfactant. Zn content, chlorophyll levels, and photosynthesis characteristics of leaves were analyzed. Leaf Zn content was significantly increased with increase of the sprayed Zn concentration of the three Zn fertilizers. However, when the sprayed Zn concentration of ZnSO4.7H2O exceeded 200 mg·L−1, and Zn concentration of ZnCl2 or Zn(NO3)2.6H2O exceeded 100 mg·L−1, obvious necrotic spots formed on leaves. This necrosis disappeared when 0.025% organosilicone was added to the three Zn fertilizer solutions, even at a Zn concentration of 250 mg·L−1. Meanwhile, the Zn contents of leaves increased one to four times for these treatments. Furthermore, foliar application of the three Zn fertilizers significantly improved chlorophyll levels and photosynthetic capacity of Zn-deficient leaves. The data of chlorophyll and photosynthesis characteristics indicate that the correcting effect of ZnCl2 and Zn(NO3)2.6H2O is better than that of ZnSO4.7H2O, and could be further improved via supplement of organosilicone. In conclusion, ZnCl2 or Zn(NO3)2.6H2O containing 250 mg·L−1 of Zn and supplemented with 0.025% organosilicone is a safe and effective formulation of Zn foliar fertilizer for correcting citrus Zn deficiency.

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Understanding of root growth patterns and architecture of apple (Malus ×domestica Borkh.) trees is very important for commercial apple production. Most commercial apple trees are usually a grafted complex consisting of the scion and the rootstock, each of which is a different genotype. Recently, rootstocks of dwarf tree species have been used extensively to meet the convenience in management; however, this practice appears to negatively impact root development. Using minirhizotrons, we investigated root dynamics, root spatial distribution, and shoot growth in ‘Red Fuji’ scion grown: 1) directly on dwarf and vigorous root stocks and 2) on a dwarf root stock placed in between the non-dwarf scion and non-dwarf rootstock (hereinafter referred to as an interstem). The results showed that: 1) one or two peaks in total root length density (TRLD) were observed in each scion/rootstock combinations every year; 2) the greatest TRLD peaks were always observed in between May and December. The peaks of shoot growth were always asynchronous with that of white root length density; 3) compared with scion/vigorous rootstock combinations, inserting a dwarfing interstem between the scion and vigorous seedling rootstock reduced the TRLD; 4) scion/vigorous rootstock combinations had a relatively deep, widespread and large root system. Scion/dwarfing rootstock combinations had a root system distributed in a small region; and the root systems of scion/dwarfing interstem/vigorous rootstock combinations tended to be intermediate between those of scion/vigorous rootstock and scion/dwarfing rootstock. This implies that the insertion of interstems altered the root architecture by not only the quantity of roots, but also the spatial distribution.

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