Revisiting the anatomy of the monocot cambium, a novel meristem

Main conclusion The monocot cambium is semi-storied, and its cells do not undergo rearrangement. Abstract The monocot cambium is a lateral meristem responsible for secondary growth in some monocotyledons of Asparagales. It is an unusual meristem, not homologous with the vascular cambia of gymnosperms and non-monocotyledonous angiosperms. Owing to the limited information available on the characteristics of this meristem, the aim of this study was to survey the structure of the monocot cambium in order to clarify the similarities and dissimilarities of this lateral meristem to the vascular cambium of trees. Using the serial sectioning analysis, we have studied the monocot cambium of three species of arborescent monocotyledons, i.e., Quiver Tree Aloe dichotoma, Dragon Tree Dracaena draco, and Joshua Tree Yucca brevifolia, native to different parts of the world. Data showed that in contrast to the vascular cambium, the monocot cambium is composed of a single type of short initials that vary in shape, and in tangential view display a semi-storied pattern. Furthermore, the cells of the monocot cambium do not undergo rearrangement. The criteria used in identifying monocot cambium initial cell are also discussed.

Plant Conservation Based on Tri Mandala Concept on Homegarden at Pakraman Penge Village, Baru Village, Marga District, Tabanan Regency, Bali

Penge Pakraman village is a traditional village that has the potency to become ecotourism. The emergence of new tourist attractions affects land changes to support tourism activities. This causes the number of plant species in nature to decrease. Plant conservation by utilizing local wisdom is one effort to reduce the decrease of plant species number. The application of Tri Hita Karana and Tri Mandala in Balinese daily life able to support plant conservation activity. The objective of this research was to determine the role of Tri Mandala concept in plant conservation at Pakraman Penge home garden. Data collection methods are carried out through observation plant location with inventory number and name of plants in house sample. Plant use continues with study literature. The results of an inventory of plant diversity in home gardens of Pakraman Penge village recorded 70 species of plants from 16 houses sample. The plant habitus varied from herbs, shrubs until trees. Plant species in the home gardens have functions for ceremonies (51%), medicinal (24%), ornamental (17%), food (6%), and spices (2%). However, based on the location, most plant species were found in madya mandala and the lowest were found in utama mandala. We also found plants with conservation status consist of least concerned (15 species), vulnerable (Dracaena draco), near threatened (Cycas rumphii), endangered (Coffea arabica). Therefore, the application of Tri Mandala concept on Balinese home gardens supports plant conservation and gives economic benefit in individual level

Aerial Root Structure and Its Significance for Function in Dracaena draco

The dragon tree, Dracaena draco, is a vulnerable species. In response to stress it forms aerial roots (AR). Although the exact function of these AR is unknown, it has been the subject of speculation on the basis of morphological observations. This study aims to investigate the structural organization of the D. draco AR compared to the background of the structure of its soil roots. The material was obtained from the collection of dragon trees growing at Jardín Botánico Canario "Viera y Clavijo" on Gran Canaria as well as from the plants obtained from the commercial nursery. Based on hand-cut sections and permanent preparations, we analysed (a) AR structure along its length encompassing the active and dormant state of the AR tip, as well as (b) the general structural organization of the soil roots (stem-borne, lateral and fine roots). We observed that AR are similar to the lateral soil roots in terms of the distribution of the primary and secondary tissues. AR are protected by rhizodermis and/or hypodermis which undergoes metacutization during the transition from the active to dormant state of the AR tip. Chloroplasts are present in cortical parenchyma cells along the entire length of the AR. The obtained anatomical findings are discussed in the context of the putative AR functions.

Complete Chloroplast Genome Sequence and Phylogenetic Inference of the Canary Islands Dragon Tree (Dracaena draco L.)

Dracaena draco, which belongs to the genus Dracaena, is an endemic succulent of the Canary Islands. Although it is one of the most popular and widely grown ornamental plants in the world, little is known about its genomic variability. Next generation sequencing, especially in combination with advanced bioinformatics analysis, is a new standard in taxonomic and phylogenetic research. Therefore, in this study, the complete D. draco chloroplast genome (cp) was sequenced and analyzed in order to provide new genomic information and to elucidate phylogenetic relationships, particularly within the genus Dracaena. The D. draco chloroplast genome is 155,422 bp, total guanine-cytosine (GC) content is 37.6%, and it has a typical quadripartite plastid genome structure with four separate regions, including one large single copy region of 83,942 bp length and one small single copy region of 18,472 bp length, separated by two inverted repeat regions, each 26,504 bp in length. One hundred and thirty-two genes were identified, 86 of which are protein-coding genes, 38 are transfer RNAs, and eight are ribosomal RNAs. Seventy-seven simple sequence repeats were also detected. Comparative analysis of the sequence data of various members of Asparagales revealed mutational hotspots potentially useful for their genetic identification. Phylogenetic inference based on 16 complete chloroplast genomes of Asparagales strongly suggested that Dracaena species form one monophyletic group, and that close relationships exist between D. draco, D. cochinchinensis and D. cambodiana. This study provides new and valuable data for further taxonomic, evolutionary and phylogenetic studies within the Dracaena genus.

First Age-Estimation Model for Dracaena ombet and Dracaena draco subsp. caboverdeana

Research Highlights: The first model for crown age estimation was developed for Dracaena ombet Heuglin ex Kotschy and Peyr. and D. draco subsp. caboverdeana Marrero Rodr. and R. Almeida. Background and Objectives: Dracaena species are monocotyledon trees without annual tree rings. Most arborescent dragon tree species are endangered; thus, it is important to determine the age structures of these populations for proper conservation management strategies, and for modelling of population trends. For these reasons, it is necessary to develop a methodology of crown age estimation. Materials and Methods: Field data were collected in the Desa’a Forest (Ethiopia) and in Santo Antão (Cape Verde Islands). Trees within each age class, as expressed by the number of branch orders, were measured. The diameter at breast height, tree height, stem height, number of branch orders, number of all leaf rosettes and number of flowering leaf rosettes within the crown were recorded for each sampled tree. The flowering probabilities were counted as input data for the model used. Results: The duration of the interval between flowering events was 5.23 years for D. ombet and 4.94 years for D. draco subsp. caboverdeana. The crown of the oldest tree of D. ombet with 18 branch orders was estimated to be 94.2 years old, and the crown of the oldest tree of D. draco subsp. caboverdeana with 22 branch orders was estimated to be 108.6 years old.