Exogenous and endogenous growth regulators on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis

This work showed for the first time the relationship between the effect of exogenous auxins and gibberellins on apogamy in Dryopteris affinis (Lowe) Fraser-Jenkins sp. affinis and its endogenous contents during early apogamic events. The addition of NAA (0.53 and 5.37 μM) or GA₃ 2.8 μM to an MS solid medium significantly increased apogamous sporophyte formation. BA induced brown callus that regenerated sporophytes in a hormone-free medium. The endogenous contents of GA₁, GA₃, GA₄, GA₇, GA₉ and IAA were determined by GC–MS in gametophytes cultured on MS solid medium, before and during early stages of apogamous embryo development. The accumulation of both GA₉ and IAA before embryo development was evident as high levels of GA₄ in the earliest analysed stage of embryo development and high levels of GA₃ in elongating shoots were found. The role of gibberellins on apogamy was also supported by data showing a decrease in the percentage of gametophytes developing embryos because of the addition of flurprimidol to the culture medium.     

Arsenic uptake and accumulation in fern species growing at arsenic-contaminated sites of southern China: field surveys

Aiming at searching for new arsenic (As) hyperaccumulators, field surveys were conducted at 12 As-contaminated sites located in Guangxi and Guangdong Provinces of southern China. Samples of 24 fern species belonging to 16 genera and 11 families as well as their associated soils were collected and As concentrations in plant and soil samples were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results show that among 24 fern species, Pteris multifida and P. oshimensis can (hyper)accumulate As in their fronds with high concentrations in addition to P. vittata and P. cretica var. nervosa, which have been previously identified as As hyperaccumulators. Total As concentrations in soils associated with P. multifida and P. oshimensis varied from 1262 to 47,235 mg kg(-1), but the DTPA-extractable As concentrations were relatively low, with a maximum of 65 mg kg(-1). Forty-four of 49 samples of P. multifida collected from five sites and 3 of 13 samples of P. oshimensis collected from one site accumulated over 1000 mg As kg(-1) in their fronds and As concentrations in the fronds were higher than those in the petioles and rhizoids. Although As concentrations in the fronds of P. oshimensis (789 mg kg(-1) averaged, range 301-2142 mg kg(-1)) were comparatively lower than those of P. multifida (1977 mg kg9-1), 624-4056 mg kg(-1)), its high aboveground biomass makes it more suitable for phytoremediating As-contaminated soils. Among all the species in Pteris genus studied, Pteris semipinnata accumulated only very low As concentration in its fronds (8 mg kg(-1), 1-18 mg kg(-1)). Further research is needed to study the differences in As uptake and accumulation among fern species in the same or other genera.     

南荻的组织培养与快速繁殖技术

以南荻幼穗为外植体,进行了组织培养与快速繁殖技术的研究。结果表明：最佳诱导培养基：MS＋2.0mg·L-12,4-D＋0.1mg·L-16-BA＋0.5g·L-1水解酪蛋白＋0.5g·L-1脯氨酸;最佳分化培养基：MS＋0.5mg·L-1NAA＋0.5mg·L-1KT＋0.5mg·L-1IAA＋2.0mg·L-16-BA＋0.5g·L-1水解酪蛋白＋0.5g·L-1脯氨酸;最佳生根培养基：MS＋1.0mg·L-1NAA＋0.25mg·L-1Met。炼苗后,移入营养土与珍珠岩（1：1）的基质中,移栽成活率高达100%。该体系的建立为南荻规模化生产及遗传改良提供了前提条件。     

Somatic embryogenesis in peach palm using the thin cell layer technique: induction, morpho-histological aspects and AFLP analysis of somaclonal variation

BACKGROUND AND AIMS: The thin cell layer (TCL) technique is based on the use of very small explants and has allowed enhanced in vitro morphogenesis in several plant species. The present study evaluated the TCL technique as a procedure for somatic embryo production and plantlet regeneration of peach palm. METHODS: TCL explants from different positions in the shoot apex and leaf sheath of peach palm were cultivated in MS culture medium supplemented with 0-600 microM Picloram in the presence of activated charcoal. The production of primary calli and embryogenic calli was evaluated in these different conditions. Histological and amplified fragment length polymorphism (AFLP) analyses were conducted to study in vitro morphogenetic responses and genetic stability, respectively, of the regenerated plantlets. KEY RESULTS: Abundant primary callus induction was observed from TCLs of the shoot meristem in culture media supplemented with 150-600 microM Picloram (83-97%, respectively). The production of embryogenic calli depends on Picloram concentration and explant position. The best response observed was 43% embryogenic callus production from shoot meristem TCL on 300 microM Picloram. In maturation conditions, 34+/-4 somatic embryos per embryogenic callus were obtained, and 45.0+/-3.4% of these fully developed somatic embryos were converted, resulting in plantlets ready for acclimatization, of which 80% survived. Histological studies revealed that the first cellular division events occurred in cells adjacent to vascular tissue, resulting in primary calli, whose growth was ensured by a meristematic zone. A multicellular origin of the resulting somatic embryos arising from the meristematic zone is suggested. During maturation, histological analyses revealed bipolarization of the somatic embryos, as well as the development of new somatic embryos. AFLP analyses revealed that 92% of the regenerated plantlets were true to type. The use of TCL explants considerably improves the number of calli and somatic embryos produced in comparison with previously described protocols for in vitro regeneration of peach palm. CONCLUSIONS: The present study suggests that the TCL somatic embryogenesis protocol developed is feasible, although it still requires further optimization for in vitro multiplication of peach palm, especially the use of similar explants obtained from adult palm trees.     

Yield components of potato microtubers: in vitro production and field performance

Genetic parameters, character association and path analysis for yield components of microtuber production in vitro and their field performance were studied in 37 potato (Solanum tuberosum L.) genotypes. Among the microtuber yield components, average microtuber weight had maximum genotypic (or phenotypic) coefficient of variation, heritability and predicted genetic advance; however, the estimated values of these genetic parameters were maximum for tuber yield among the field yield components. The heritability estimates of field yield components were higher than that of their corresponding in vitro yield components of microtuber production. The highest correlation coefficients between average microtuber weight and microtuber yield suggested that microtuber weight was more important than microtuber number in determining microtuber yield potential in vitro. However, tuber number was found to be more important than tuber weight in determining tuber yield potential under field conditions. Average microtuber weight had maximum direct effect on microtuber yield, whereas tuber number had maximum direct effect on tuber yield under field conditions. The study showed that the relative importance of the components of microtuber production in vitro differed from that of corresponding field yield components. The expression of a genotype for microtuber production in vitro is different from that of tuber production under field situation i.e. the performance of a genotype in vitro is not a measure of its field performance.