Cytogenetic effects in the needles intercalar meristem of Japanese red pine in the remote period after the Fukushima NPP accident

Background. The study of the long-term effects of chronic radiation exposure on plants and animals, which are still the subject of scientific discussion, is necessary to understand the consequences of radiation accidents. After the Fukushima nuclear power plant accident, some of the young pines and spruces showed an increased frequency of apical dominance cancelling. The most probable cause of the observed morphoses is associated with damage to the apical meristem of coniferous plants by radiation in the first year of the accident, when they received the highest absorbed doses. If this hypothesis is true, then even 8 years after the accident it will be possible with high degree of probability to detect an increased level of cytogenetic abnormalities in the intercalary meristem of needles of plants from these populations. The aim of this work was to verify this hypothesis. Materials and methods. Five populations of Japanese red pine from territories contaminated with radionuclides as a result of the accident at the Fukushima nuclear power plant were investigated. The frequency and spectrum of cytogenetic abnormalities in the intercalary meristem of needles were determined by the ana-telophase analysis. Results. The frequency of aberrant cells in the needles intercalary meristem of Japanese red pine from the contaminated with radionuclides territory statistically significantly exceeds the control level in all impact sites and increases along with the dose rate. Although there is no correlation between the frequency of cytogenetic abnormalities in needles and the presence of cancellation of apical dominance in plants, all pine populations from radioactively contaminated territories are characterized by an increased frequency of both cytogenetic abnormalities and morphoses associated with the cancellation of apical dominance. Conclusion. Radiation damage to the apical meristems of conifers in the first year of the accident, when they received the highest absorbed doses, is the most likely cause of the increased frequency of cancellation of apical dominance in the studied populations of Japanese red pine from the zone affected by the accident at the Fukushima nuclear power plant.

Maize brachytic2 (br2) suppresses the elongation of lower internodes for excessive auxin accumulation in the intercalary meristem region

Background Short internodes contribute to plant dwarfism, which is exceedingly beneficial for crop production. However, the underlying mechanisms of internode elongation are complicated and have been not fully understood. Results Here, we report a maize dwarf mutant, dwarf2014 (d2014), which displays shortened lower internodes. Map-based cloning revealed that the d2014 gene is a novel br2 allele with a splicing variation, resulting in a higher expression of BR2-T02 instead of normal BR2-T01. Then, we found that the internode elongation in d2014/br2 exhibited a pattern of inhibition-normality-inhibition (transient for the ear-internode), correspondingly, at the 6-leaf, 12-leaf and 14-leaf stages. Indeed, BR2 encodes a P-glycoprotein1 (PGP1) protein that functions in auxin efflux, and our in situ hybridization assay showed that BR2 was mainly expressed in vascular bundles of the node and internode. Furthermore, significantly higher auxin concentration was detected in the stem apex of d2014 at the 6-leaf stage and strictly in the node region for the ear-internode at the 14-leaf stage. In such context, we propose that BR2/PGP1 transports auxin from node to internode through the vascular bundles, and excessive auxin accumulation in the node (immediately next to the intercalary meristem) region suppresses internode elongation of d2014. Conclusions These findings suggest that low auxin levels mediated by BR2/PGP1 in the intercalary meristem region are crucial for internode elongation.

Pengujian berbagai eksplan kentang (Solanum tuberosum L.) dengan penggunaan konsentrasi BAP dan NAA yang berbeda

Rendahnya produksi kentang di Indonesia disebabkan oleh ketersediaan benih kentang bermutu hasil dari metode konvensional yang kurang memadai. Metode kultur jaringan mampu menghasilkan bibit bermutu dan bebas virus, dalam jumlah banyak serta waktu yang singkat. Penelitian ini bertujuan untuk mendapatkan konsentrasi 6-benzylaminopurine (BAP) dan Naphthalene Acetic Acid (NAA) terbaik pada berbagai eksplan untuk pertumbuhan tunas meriklon kentang (Solanum tuberosum L.) Kultivar Atlantik secara in vitro. Percobaan dilaksanakan pada November 2016 sampai Februari 2017 di Laboratorium Kultur Jaringan Teknologi Benih Fakultas Pertanian Universitas Padjadjaran. Rancangan Acak Lengkap (RAL) digunakan sebagai rancangan percobaan yang terdiri dari dua unit percobaan terpisah yaitu unit eksplan meristem interkalar dan meristem apikal, masing-masing delapan perlakuan dan empat ulangan. Media Murashige and Skoog (MS) digunakan sebagai media dasar dengan penambahan BAP (0,0 mg L-1; 1 mg L-1; 1,5 mg L-1; 2 mg L-1) dan NAA (0,0 mg L-1; 0,5 mg L-1). Hasil menunjukkan konsentrasi BAP 1 mg L-1 merupakan perlakuan yang paling baik dalam menghasilkan jumlah tunas, cabang, daun dan buku pada eksplan meristem interkalar. Pada eksplan meristem apikal, penambahan BAP dan NAA belum mampu meningkatkan pertumbuhan eksplan. Meristem interkalar yang diberi auksin dan sitokinin berpotensi menjadi bahan alternatif eksplan meriklon kentang selain meristem apikal. The production of potato in Indonesia is low due to the limited number of high quality potato seeds produced from the conventional methods. The tissue culture methods can be used to produce high quality and virus-free seeds in more reliable number in a short time. Randomized Completely Design (RCD) was used as the experimental design consisted of two separate trial units namely intercalary meristem and apical meristem explants units with eight treatments and four replications of each. Murashige and Skoog (MS) was used as the base media added with BAP i.e. 0.0 mg L-1; 1 mg L-1; 1.5 mg L-1; 2 mg L-1 and NAA 0.0 mg L-1 and 0.5 mg L-1. Results showed that concentration of BAP 1 mg L-1 generated the best results on the number of shoots, branches, leaves and nodes on meristem intercalary explant. Meanwhile on apical meristem explant, the addition of BAP and NAA had not yet improved the explant growth. Intercalary meristem added with auxin and cytokinin is potential as alternative of mericlone explants material of potato besides the apical meristem.

Morphoanatomy of the underground system of Androtrichum trigynum (Cyperaceae)

Androtrichum has only one species, A. trigynum (Spr.) Pfeiffer, occurring in coastal regions of the southwestern Atlantic coast. It presents an underground system consisting of rhizomes and adventitious roots. The rhizome is thickened, plagiotropic, sympodial, and floral scapes and roots arise from it. From the stem promeristem, the protoderm, procambium and ground meristem are differentiated. At the apex region, the intercalary meristem and primary thickening meristem (PTM) are observed. The adventitious roots originate from the PTM, and present root apex with closed organization. The young epidermis has papillose cells, and meristematic endoderm activity is observed. In a mature root, the outer cortex, or hypodermis, and the internal cortex can be identified. The endoderm presents radially elongated cells with thin walls and the pericycle is biseriate. The anatomical features observed in the present study are found in other species of Cyperaceae and some xeromorphic characters can be identified.

Diversity of cell lengths in intercalary meristem regions of grasses: location of the proliferative cell population

Intercalary meristems are responsible for the production of the majority of cells in stems. The overall objective of the present study was to determine (i) the boundaries of the proliferative parenchyma cells in the intercalary meristems and (ii) the proliferative capacity of cells in the intercalary meristems in stems of a species of Bambusa Schreb. (bamboo), Phragmites australis (Cav.) Trin. ex Steud., Triticum aestivum L., and Zea mays L. Data show that lengths of parenchyma cells within proliferative portions of intercalary meristems were not the same for all intercalary meristems of a species. Lengths of elongated parenchyma cells in internodes were relatively similar among internodes of a species, but lengths of elongated parenchyma cells in internodes were not similar among the four grass species tested. For example, cell lengths of elongated parenchyma cells in internodes of P. australis ranged from 14.8 to 23.0 µm, very different from lengths of elongated cells in Bambusa sp. (69.1–75.4 µm). The number of proliferative cells in most files of intercalary meristems of Bambusa was less than 15. For many of the intercalary meristems of P. australis, the intercalary meristem consisted of 10–25 cells in each file. Fourth intercalary meristems of T. aestivum and Z. mays consisted of 20 and 25 cells in files, respectively. Data showed that none of the cell populations of the intercalary meristems of four species exhibited an exponential cell length distribution. In general, less than half of the 10 groups of cells had percentages of cells that resembled an exponential cell-age distribution. These data lead to the conclusion that not all parenchyma cells of intercalary meristems are rapidly proliferating. Also, potentially prolifera tive cells (short cells) of the intercalary meristems may not be localized into a specific zone but are more scattered throughout the nodal region.Key words: intercalary meristems, proliferative cell populations, Gramineae, cell lengths.

A Study of the Vascular Organization of Bamboos (Poaceae-Bambuseae) Using a Microcasting Method

A reliable and simple microcasting method is applied to the study of the vascular structure in bamboo nodes; it provides new insights into their complexity, revealing the exact arrangement of branched vessels and clustered tracheary elements. Axial differentiation gradients in the metaxylem cell files, probable relics of the intercalary meristem, can also be found using this method. This anatomical finding can be linked to arecent hypothesis on the continuum in the tracheary element differentiation.