The influence of desiccation and rehydration on the survival of polyembryonic seed of Citrus suhuiensis cv. limau madu

A study was carried out to investigate the influence of desiccation and freezing followed by various presowing rehydration procedures on the desiccation sensitivity of the seed of Citrus suhuiensis cv. limau madu. The freshly harvested seeds of limau madu were desiccated under a broad range of relative humidity (RH) to various equilibrium water contents (g H₂O g⁻¹ dw). The desiccated and desiccated–frozen seeds were either directly sown under germination conditions or subjected to presowing rehydration procedures: seed preheating, prehumidification and osmoconditioning. The hydrated and desiccated seeds were sown in controlled germination conditions and the survival was evaluated 4–6 weeks after sowing. The results showed that desiccation progressively reduced the percentage of normal seedling of the seeds of limau madu and the viability is almost lost at water contents below 0.08 g H₂O g⁻¹ dw. The estimated desiccation sensitivity was substantially high (WC₅₀ = 0.143 g H₂O g⁻¹ dw) when the desiccated seeds were rapidly rehydrated (uncontrolled rehydration). In contrast, seed prehumidification, preheating and osmoconditioning (controlled rehydration procedures) markedly enhanced normal seedling percentages decreasing the estimated values of WC₅₀ (between 0.08 and 0.127 g H₂O g⁻¹ dw). While the rapidly rehydrated desiccated–frozen seeds were almost killed at water content of 0.15 g H₂O g⁻¹ dw, prehumidification and preheating have noticeably increased percentage of frozen seeds survival at the same water content. However, at water content of 0.21 g H₂O g⁻¹ dw preheating significantly (P < 0.05) increased percentage of normal seedling of the frozen seeds. Seed desiccation markedly reduced the percentages of germinated seeds with multiple seedlings. Seed controlled rehydration remarkably increased the survival of polyembryos. The beneficial effect of seed controlled rehydration on the survival of the desiccated seeds was pronounced at medium water contents (0.08–0.25 g H₂O g⁻¹ dw).     

Physico-chemical properties and antioxidant capacity of different jujube (Ziziphus jujuba Mill.) cultivars grown in loess plateau of China

The physico-chemical properties and antioxidant capacity of the five main jujube varieties: Junzao, Lingbaozao, Jinzao, Zanhuangzao and Lizao collected from loess plateau of China were determined. The analyzed components included fruit yield, moisture content, total mass per fruit, pH, titratable acidity (TA), reducing sugars, total sugars, total soluble solids (TSS), ascorbic acid, total phenolics content, total flavonoids content and several pure phenolic compounds. The output of the analyses showed higher amounts of ascorbic acid and phenolics in these jujube varieties than in some common fruits. The antioxidative capacity of the jujube extracts, evaluated with the reducing power, the β-carotene bleaching, the 2,2-diphenyl-1-picrylhydracyl (DPPH•), and the 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonicacid) (ABTS•⁺) scavenging methods, showed that the antioxidant activity of the extracts of Lingbaozao was excellent for free radical scavenging and a potent natural antioxidant of commercial value. Statistically significant differences were observed between jujube cultivars investigated with regards to the measured parameters except rutin content of fruit. These results demonstrated that the cultivar was the main factor which influences the physico-chemical properties and antioxidant activity of jujubes.     

Arginine metabolism in roots and leaves of apple (Malus domestica Borkh.): The tissue-specific formation of both nitric oxide and polyamines

In addition to serving as an important nitrogen reserve, l-Arginine participates in various physiological processes in plants. In plants, like in animals, nitric oxide (NO) is synthesized through nitric oxide synthase (NOS) pathway, while polyamines (PAs) are through arginine decarboxylase (ADC) and/or arginase–ornithine decarboxylase (ODC) pathway in arginine metabolism. In this study, arginine metabolism in fine roots and leaves of different development stages (white roots, brown roots, young leaves and mature leaves) were investigated, using potted 3-year-old apple plants. The results showed that different pathways in arginine metabolism are positively correlated, producing polyamines and nitric oxide in a tissue-specific manner. Higher levels of arginine, polyamines and nitric oxide, as well as arginase, ADC, ODC and NOS activities exist in roots than in leaves. White roots and young leaves exhibit higher levels of arginine metabolism than brown roots and mature leaves, respectively. As both polyamines and nitric oxide are multifunctional molecules involved in plant development and stress response, it is possible to conclude that the unique physiological roles of l-Arginine in plants might be associated with the coordinated biosynthesis of both polyamines and nitric oxide via arginine metabolism.     

High frequency multiplication of Phalaenopsis gigantea using trimmed bases protocorms technique

This study was conducted to determine the effects of coconut water (CW) and activated charcoal (AC) on multiplication of Phalaenopsis gigantea protocorms. The protocorms used for this study were obtained by germinating seeds in vitro. Protocorms with trimmed and untrimmed bases were cultured on XER basal medium containing 0, 10, 15 or 20% (v/v) CW; and 0, 1, 2 or 2.5 g AC l⁻¹. Trimmed protocorms exhibited the highest percentage of proliferation on a medium containing 15% (v/v) CW and 2.5 g AC l⁻¹ (56.82 ± 38.86%) with an average of 4.24 ± 2.89 protocorms formed per protocorm. Untrimmed protocorms cultured on a medium containing 20% (v/v) CW without AC produced the highest percentage of new protocorms (6.93 ± 6.28%) with an average of 0.72 ± 0.57 per protocorm. When CW was added to a medium singly, 10% (v/v) CW induced a higher degree of proliferation on trimmed protocorms (5.68 ± 10.14%) with an average 0.50 ± 0.84 new protocorms per protocorm. Untrimmed protocorms proliferate to a much lower extent (2.57 ± 2.74%) with an average of 0.72 ± 0.57 protocorms per protocorm when cultured on a similar medium. A high concentration of CW enhanced proliferation on untrimmed protocorms, but increased mortality of trimmed protocorms. The addition of CW with AC to media increased protocorm proliferation and survival of both trimmed and untrimmed protocorms. When cultured on all media, trimmed protocorms produced a higher number of new protocorms (an average 0.5–7.0) as compared to untrimmed protocorms (0.3–1.9). Comparative studies showed that trimmed protocorms produced up to 10 times more new protocorms than untrimmed ones. Altogether this study showed that trimmed protocorms cultured on a medium containing CW and AC can be used for high-frequency multiplication of P. gigantea seedlings.     

Production of protocorm-like bodies with bioreactor and regeneration in vitro of Oncidium ‘Sugar Sweet’

To produce mass propagules of Oncidium ‘Sugar Sweet’, we tested the feasibility of producing protocorm-like bodies (PLBs) using 5 l balloon type air-lift bioreactors, and selected an optimal culture medium for shooting and rooting in vitro. The results showed that liquid bioreactor cultures were more efficient for PLBs proliferation when compared to solid- and liquid-agitated flask cultures. The maximum PLBs biomass (326.3 g per bioreactor, FW) was obtained in the immersion bioreactor culture, with the growth ratio reaching 10.9 after 50 days of culture. This was obviously higher than the ebb and flood bioreactor culture. During bioreactor culture, sucrose and electric conductivity (EC) in the culture medium were negatively correlated with PLBs growth; the highest PLBs fresh and dry biomass was obtained 40 days after culture. An inoculation density of 20 g (FW) was optimal for PLBs growth in a 3 l working volume of 5 l bioreactor. Furthermore, MS medium supplemented with 2.0 mg l⁻¹ BA for shooting and 0.5 mg l⁻¹ IBA for rooting was optimal during in vitro culture, the plantlets were successfully established in the potting substrate.     

Evaluation of citrus somatic hybrids for tolerance to Phytophthora nicotianae and citrus tristeza virus

Somatic hybridization is a biotechnology tool that can be used in citrus breeding programs to produce somatic hybrids with the complete genetic combination of both parents. The goal of this work was to test the reaction of citrus somatic hybrids that may be useful as rootstocks to trunk and root infections caused by Phytophthora nicotianae van Breda de Haan (P. parasitica Dastur) and to citrus tristeza virus (CTV). The somatic hybrids evaluated were ‘Caipira’ sweet orange (Citrus sinensis L. Osbeck) + ‘Rangpur’ lime (C. limonia Osbeck), ‘Caipira’ sweet orange + ‘Cleopatra’ mandarin (C. reshni hort. ex Tanaka), ‘Caipira’ sweet orange + ‘Volkamer’ lemon (C. volkameriana V. Ten. & Pasq.), ‘Caipira’ sweet orange + rough lemon (C. jambhiri Lush.), ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Cleopatra’ mandarin + sour orange (C. aurantium L.), ‘Rangpur’ lime + ‘Sunki’ mandarin (C. sunki (Hayata) hort. ex Tanaka), ‘Ruby Blood’ sweet orange (C. sinensis L. Osbeck) + ‘Volkamer’ lemon, ‘Rohde Red’ sweet orange (C. sinensis L. Osbeck) + ‘Volkamer’ lemon, and ‘Valencia’ sweet orange + Fortunella obovata hort. ex Tanaka. For P. nicotianae trunk and root infection assays, plants of the somatic hybrids, obtained from 9-month semi-hardwood cuttings, were evaluated and compared with diploid citrus rootstock cultivars after mycelia inoculation in the trunk or spore infestation in the substrate, respectively. ‘Cleopatra’ mandarin + sour orange, ‘Rangpur’ lime + ‘Sunki’ mandarin, ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Ruby Blood’ sweet orange + ‘Volkamer’ lemon, ‘Rohde Red’ sweet orange + ‘Volkamer’ lemon, and ‘Caipira’ sweet orange + ‘Volkamer’ lemon had less trunk rot occurrence, whereas the somatic hybrids ‘Cleopatra’ mandarin + ‘Volkamer’ lemon, ‘Cleopatra’ mandarin + sour orange, ‘Caipira’ sweet orange + ‘Volkamer’ lemon, and ‘Caipira’ sweet orange + ‘Rangpur’ lime were tolerant to root rot. For CTV assays, plants of the somatic hybrids along with tolerant and intolerant rootstocks were budded with a mild strain CTV-infected or healthy ‘Valencia’ sweet orange budwood. Differences in average scion shoot length indicated that the hybrids ‘Cleopatra’ mandarin + sour orange and ‘Valencia’ sweet orange + Fortunella obovata were intolerant to CTV.     

Development of zygotic and somatic embryos of Phoenix dactylifera L. cv. Deglet Nour: Comparative study

In order to improve somatic embryogenesis production in date palm Phoenix dactilyfera L. cv. Deglet Nour (DN), a comparative study between somatic (SE) and zygotic (ZE) embryos developments was carried out. The data showed that ZE maturation occurred from 10 to 19 weeks after pollination (WAP). During this period, the fresh weight (FW) and the dry weight (DW) of ZE increased progressively to reach a maximum level at 19 WAP. SE development occurred in three distinct stages. The DW remained constant during the two first stages, and declined slightly during the third and final stage. Embryo protein analysis revealed significant differences between ZE and SE. The ZE total protein level was initially low and increased to the maximum at mature stage. However, no significant change in total protein was detected during SE development. SDS-PAGE analysis showed a poor protein profile for SE, compared to that of ZE. In the latter, a 22 kDa protein was identified by N-terminal sequencing as a glutelin. This protein was accumulated rapidly during early development and remained at a relatively constant level during ZE development, and then declined progressively 12 days after embryo germination (DG). This protein seems to be absent in SE.     

Confirmation of Clematis hybrids using molecular markers

The hybrid origin of progeny from crosses of Clematis tubulosa and Clematis brevicaudata was investigated using randomly amplified polymorphic DNA (RAPD) and single nucleotide polymorphisms (SNPs) from sequence analysis of chloroplast rbcL, accD genes, and the C. brevicaudatamatK gene. Plants collected from three and four populations of C. brevicaudata (C. brev) and C. tubulosa (C. tubu), respectively, from Mt. Songshan, Beijing, China were used as parents for hybridization. Morphological characters of pollen, seeds, and leaves were recorded in 2007. DNA from leaf samples of both parents and of C. brev × C. tubu and C. tubu × C. brev were extracted, and used for RAPD and SNPs from sequence data. A dendrogram was constructed by the branching neighbor-joining (IB-NJ) method. Proportionate population scores were generated by the admixture model using the STRUCTURE software. Based on morphological characters, C. brevicaudata was quite uniform. However, variations were detected in C. tubulosa. Hybrids of C. brev × C. tubu and C. tubu × C. brev showed intermediate morphological characters of the parents. Accessions of C. tubu × C. brev were clustered into 2 groups, with the majority of hybrids belonging to group IV b in the RAPD dendrogram, suggesting that this resulted from variations within C. tubulosa. In general, the hybrid origin of all progeny characterized by morphological characters was supported by the RAPD and SNPs data. These results indicate that RAPD results supported by SNPs data will be useful tool to verify hybrids.     

Interspecific variations in seed germination of Corylopsis

This study was initiated to investigate the differences in germination percentages and rates between Corylopsis coreana Uyeki and Corylopsis sinensis var. calvescens Rehder & E.H. Wilson following a warm stratification (WS) and cold stratification (CS), and to study the effect of different WS temperatures interacting with different durations of CS. Warm stratification at 10 °C, 15 °C, 20 °C, and 25 °C was given for 1 month (1 M 10 °C, 15 °C, 20 °C, and 25 °C WS) followed by 0 M, 1 M, 2 M, and 3 M of CS at 5 °C (0 M, 1 M, 2 M, 3 M CS) and seeds were germinated in an air conditioned greenhouse maintained at 18.5 °C/18 °C. On average, less than 1% of C. coreana seeds germinated when sown without any WS and CS or with 1 M 15 °C, 20 °C, and 25 °C WS without CS treatment. However, 26% C. coreana seeds germinated after 1 M 10 °C WS without any CS treatment. Germination was not affected by WS temperatures when followed by 2 M 5 °C CS. It is concluded that C. coreana exhibited low seed germination at 10 °C and that this temperature could be considered the upper limit of CS for C. coreana. Only 2 M CS was required for more than 90% seeds to germinate. However, C. sinensis var. calvescens required longer than 3 M CS for more than 29% seeds to germinate. This clearly shows that there is an interspecific variation in optimum dormancy-breaking requirements.     

Effect of 2,4-d, glutamine and BAP on embryogenic suspension culture of date palm (Phoenix dactylifera L.)

The proliferation of embryogenic suspension culture in two cultivars (Jihel and Bousthami Noir) of Phoenix dactylifera L. was tested on liquid media with or without 2,4-d and with different glutamine concentrations (3.35 × 10⁻⁴, 6.7 × 10⁻⁴ and 13.4 × 10⁻⁴ M). The liquid medium with 0.1 mg l⁻¹ 2,4-d and 6.7 × 10⁻⁴ M glutamine has clearly improved the proliferation of somatic embryos. In fact, when glutamine concentration increased from 3.35 × 10⁻⁴ to 6.7 × 10⁻⁴ M, the yield of somatic embryos increased from 14 to 56 embryos per 100 ml of culture medium for “Jihel” cultivar and 25–71 embryos per 100 ml of culture medium for “Bousthami Noir” cultivar. In contrast, increasing glutamine concentration from 6.7 × 10⁻⁴ to 13.4 × 10⁻⁴ M, the embryos yield was negligible. Based on biochemical analysis, the highest accumulation of proteins and sugars was obtained in liquid medium with 0.1 mg l⁻¹ 2,4-d and 6.7 × 10⁻⁴ M glutamine (118 and 91 mg of proteins g⁻¹ DW, respectively, for “Jihel” and “Bousthami Noir” cultivars; 194 mg of sugars g⁻¹ DW for “Jihel” cultivar and 182 mg of sugars g⁻¹ DW for “Bousthami Noir” cultivar). In addition, the supply of 0.05 mg l⁻¹ BAP on the germination medium could be useful in terms of germination percentage of somatic embryos. When BAP concentration increased from 0.05 to 0.2 mg l⁻¹, the germination percentage of somatic embryos decreased from 14.2 to 4.9%, while secondary embryogenesis increased from 26.4 to 45.2%.     

The influence of flesh colour and growing locality on polyphenolic content and antioxidant activity in potatoes

Compounds contained in potato tubers that may act as antioxidants have been attracting increased attention. The main antioxidants in potatoes are polyphenolic compounds. The total polyphenolic (TP) content and antioxidant activity (AA) in potato tubers of four yellow-fleshed cultivars and two purple-fleshed cultivars from the 2004 harvest were tested. The total polyphenolic content was determined using the Folin-Ciocalteau reagent (FC) and the antioxidant activity, with the DPPH method using stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH·). Significant differences were found in total polyphenolic content between the yellow-fleshed cultivars Karin, Impala, Ditta, and Saturna. Significant differences between yellow and purple-fleshed potatoes were found: the yellow-fleshed cultivars had an average of 2.96 g gallic acid equivalents (GAE) per kg DM, the purple-fleshed cultivars 4.68 g GAE per kg DM. Significant differences in AA between the yellow and purple-fleshed cultivars were determined (yellow-fleshed in an average of 139.3 mg equivalents of ascorbic acid [EAA] per kg DM, purple-fleshed 332.3 mg EAA per kg DM) as well as between the purple-fleshed cultivars Valfi (298 mg EAA per kg DM) and Violette (366 mg EAA per kg DM). The major antioxidants in purple-fleshed cultivars were anthocyanidins petunidin (Valfi 92%_rel) and malvidin (Violette 85%_rel). Cv. Violette contained three times higher content of anthocyanidins than cv. Valfi. Among four experimental localities, the higher situated potato-growing region of Stachy (locality with the lowest average annual and daily minimum temperatures and the highest sum of precipitation in the vegetative period) differed significantly from other localities by a higher TP content, AA and yield in the analyzed cultivars. A high positive correlation between antioxidant activity and total polyphenolic content with R = 0.8648, R² = 0.7478 (P = 0.0001) was found.     

Correlation of saponin content and Fusarium resistance in hybrids from different ploidy levels of Lilium Oriental

Lilium Oriental is of great commercial value, but large losses in production can result from its susceptibility to diseases caused by Fusarium ssp. Here we report a mutant of Lilium Oriental resistant to Fusarium, Cai-74, which was generated from crossing tetraploid (from ‘Star fighter’) and diploid (‘Cor. Amore’ × ‘Acapulco’) plants. Hybrid progeny were screened via inoculating Fusarium oxysporum into tissue cultured plantlets in a greenhouse. Although Cai-74 had a saponin content of 3.81 mg g⁻¹, which is much higher than its parents, the highly Fusarium-resistant wild species Lilium dauricum had the highest content of 4.11 mg g⁻¹ among the tested genotypes. Cai-74 had a 3A karyotype rather than 3B found in normal plants of Lilium Oriental. Taken together, our results suggest that Cai-74 bears a chromosomal variation in its structure, and that the saponin content in the lily scales correlate with the Fusarium resistance of Lilium Oriental. Cai-74 could be used as a gene resource for breeding Fusarium-resistant cultivars of Lilium Oriental.     

Production of inter-section hybrids between Primula filchnerae and P. sinensis through ovule culture

Inter-section hybrids were obtained in the reciprocal crosses between Primula filchnerae (2n = 2x = 24) of Sect. Pinnatae and P. sinensis ‘Fanfare’ (2n = 2x = 24) of Sect. Auganthus by rescuing ovules on half-strength (1/2) Murashige and Skoog's (MS) medium supplemented with 50 g l⁻¹ sucrose, 2.5 g l⁻¹ gellan gum, 0.1 mg l⁻¹ α-naphthaleneacetic acid (NAA), 0.1 mg l⁻¹ 6-benzyladenine (BA) and 50 mg l⁻¹ gibberellic acid (GA₃). In ovule culture, germination occurred with radicle elongation but no plumule was observed. The radicle kept on the initial medium showed root proliferation with callus formation. When the calluses were transferred to (1/2)MS media containing 30 g l⁻¹ sucrose and 3 g l⁻¹ gellan gum, without plant growth regulators (PGRs) or with 1 mg l⁻¹ zeatin and 0.1 mg l⁻¹ NAA, plantlets were regenerated. The plants thus obtained were confirmed to be hybrids through flow cytometry (FCM) and random amplified polymorphic DNA (RAPD) analyses. The hybrid obtained when P. filchnerae was used as the maternal parent was diploid, whereas hexaploid hybrid was obtained when using P. sinensis as the maternal parent. The hexaploid hybrid might be produced through chromosome doubling of a triploid originated from the fertilization of P. sinensis with unreduced pollen of P. filchnerae.     

6-Benzylamino purine stimulates in vitro shoot organogenesis in Eucalyptus erythronema, E. stricklandii and their interspecific hybrids

In vitro bud and shoot organogenesis was investigated for the ornamental plants Eucalyptus erythronema var. erythronema, E. stricklandii and their interspecific hybrids cv. ‘Urrbrae Gem’ and ‘Hybrid 2.5’ by using 0.0, 0.1, 0.25, 0.5 or 1.0 μM BAP on apex and leaf explants. Callus developed on all explants and increased with all concentrations of BAP without significant differences between BAP concentrations. Buds formed on apex and leaf explants of E. erythronema and E. cv. ‘Urrbrae Gem’ especially with 1.0 μM BAP, but these buds rarely developed into shoots. Bud clusters formed on E. erythronema and E. cv. ‘Urrbrae Gem’ apex and leaf explants whereas E. stricklandii and ‘Hybrid 2.5’ produced fewer, individual buds on the explant. Shoots regenerated from apex explants of all genotypes with all levels of BAP, whereas few shoots of any genotype regenerated from leaf explants regardless of the number of buds formed. Shoots from apex explants could be multiplied successfully. Light microscopy showed meristems developed within the callus, and at the callus and bud surfaces. However, few shoots developed considering the level of bud and meristem formation. This report is the first for successful shoot organogenesis and multiplication in an ornamental eucalypt.     

Effects of seed maturity,seed storage and pre-germination treatments on seed germination of cleome (Cleome gynandra L.)

The influence of seed maturity, seed storage and germination pre-treatments on seed germination of cleome (Cleome gynandra L.) were investigated. Seed maturation studies showed that capsules harvested at 18 days after anthesis possessed the highest dry weight with 19.2% moisture and 1% germination. Development of fresh-ungerminated seed was observed with increasing maturity of fruit, suggesting that cleome exhibited forms of seed dormancy. Storing mature seed at 15 °C and at room temperature for 5 months showed that seed dormancy was broken after 3 months under both storage regimes. When mature seeds were subjected to different treatments including various levels of GA₃, KNO₃, leaching, pre-chilling, soaking and pre-heating at different temperatures, it was found that pre-heating at 40 °C for period of 1–5 days was the most effective method in breaking dormancy in cleome.     

Antioxidant potency of white (Brassica oleracea L. var. capitata) and Chinese (Brassica rapa L. var. pekinensis (Lour.)) cabbage: The influence of development stage,cultivar choice and seed selection

The accumulation of total phenols (TP, Folin-Ciocalteu method) and total flavonoids (TF, colorimetric assay with AlCl₃) and the evolution of antioxidant capacity (FRAP assay, DPPH and ABTS radical scavenging assays) have been monitored in juices of Croatian white cabbage (Brassica oleracea var. capitata) cultivars Vara?dinski and Ogulinski, as well as Chinese cabbage (Brassica rapa var. pekinensis), at various developmental stages. Measurements were performed every four weeks, starting from planting to full maturity, throughout the course of eight months. In the first 8–12 weeks, the TP and TF contents as well as antioxidant capacity increased significantly in all analyzed juice samples and in most even doubled. This rapid increase was followed by a gradual decrease in values derived from all assays, over the course of 12–30 weeks, to the final values which were in all cases lower than the values measured at week 4. The results also point to significant variability in TP and TF contents and antioxidant capacity at the fully mature stage between white and Chinese cabbage juices and between juices extracted from cultivars Ogulinski and Vara?dinski.     

Production of intraspecific hybrids between wild-type and petaloid-sepal cultivars in Habenaria radiata

Orchids are commercially important plants with flowers that are unique and very specialized in shape and color. The flowers consist mostly of sepals, lateral petals, lip (labellum) and column, and are zygomorphic and resupinate. Whereas most orchid species have petaloid tepals in the first and second whorls, Habenaria radiata has a flower with greenish sepals and white lateral petals and lip. ‘Hishou’, one of the cultivars of H. radiata, is a floral homeotic mutant and has a petaloid median sepal and lip-like lateral sepals in the first whorl. Additionally, this cultivar often has non-resupinate flowers whereas wild-type H. radiata flowers are resupinate. In the present study, we investigated the genetic inheritance of these characters in the ‘Hishou’ cultivar by crossing it with wild-type plants. Some intraspecific hybrids, which were confirmed by PCR-RFLP analysis, had flowers with a petaloid median sepal and lip-like lateral sepals in the first whorl, indicating that these were dominant characters. Since the remainder of the intraspecific hybrids had wild-type flowers, these characters must be heterozygous in ‘Hishou’ plants. Although ‘Hishou’ plants had non-resupinate flowers, intraspecific hybrid flowers were resupinate, even though they had the petaloid median sepal and lip-like lateral sepals. This result indicates that non-resupination must be a recessive character. Since sepal-petalization and triple lip characters of ‘Hishou’ inherited dominantly, these characters can be utilized for the breeding of Habenaria species by intra- and interspecific crosses.     

Evaluation of strains of Poncirus trifoliata and trifoliate orange hybrids for resistance to Phytophthora root rot

Ten strains of Poncirus trifoliata (L.) Raf. and 6 trifoliate orange hybrids were evaluated for resistance to root rot caused by Phytophthora nicotianae B. de Haan var. parasitica (Dast.) Waterh. A high degree of resistance was shown by Rubidoux trifoliate and Trifoliate orange (Srirampur). Trifoliate orange hybrids, in general, were less resistant than P. trifoliata strains. The usefulness of different parameters in the assessment of root damage are briefly discussed.     

In vitro asymbiotic seed germination and seedling growth of Ansellia africana Lindl.

The effects of sodium hypochlorite treatment and growth medium on in vitro seed germination and seedling growth of the leopard orchid (Ansellia africana Lindl.) were investigated. Forty minutes treatment of seeds with 1.75% sodium hypochlorite stimulated germination (70.6%) and seedling development when measured at Stage 5 (emergence of first leaf) on P668 medium after 8 weeks of culture. The growth medium played a significant role in determining the germination response of A. africana seeds. Dark pretreatment of seed cultures significantly enhanced the germination percentage and the growth of rhizoids on the protocorms. Leaf growth in terms of length was substantially enhanced on P668 medium. It was significantly reduced in modified Knudson C medium after 16 weeks of culture. Seedlings developed on P668 medium showed a significantly better growth performance in relation to leaf length, leaf number, root length, fresh and dry weights per plant in vermiculite after 12 weeks of ex vitro growth in a mist house with 90% relative humidity. Further studies developing a suitable method for in vitro symbiotic germination could assist in reintroduction of this threatened orchid species into the wild.     

硫对设施水培大蒜光合特性和鳞茎品质的影响

在设施条件下,采用营养液培养大蒜,研究不同施硫水平对其光合特性、鳞茎质量及品质的影响。结果表明,在施硫水平0 ~ 2.25 mmol · L-1范围内,光合速率（Pn）、叶绿素含量、气孔导度（Gs）、蒸腾速率（E）和鳞茎质量随施硫量增加而升高,至硫浓度2.25 mmol · L-1时达最高。鳞茎品质指标除可溶性蛋白质外,随植株生长而逐渐升高。在不同硫处理间,鳞茎中大蒜素、可溶性糖和游离氨基酸和蒜薹中大蒜素、可溶性糖、维生素C及游离氨基酸含量均以2.25 mmol · L-1硫处理最高,分别比不施硫处理增加48.82%、127.92%、63.58%、10.61%、63.30%、29.07%和74.16%。营养液中硫含量为3.75 mmol · L-1时,鳞茎中蛋白质含量最高。大蒜二次生长指数在一定硫浓度范围内,随硫水平的升高而降低,而后随施硫量的升高变化不显著。