The Making of Plant Armor: The Periderm

The periderm acts as armor protecting the plant's inner tissues from biotic and abiotic stress. It forms during the radial thickening of plant organs such as stems and roots and replaces the function of primary protective tissues such as the epidermis and the endodermis. A wound periderm also forms to heal and protect injured tissues. The periderm comprises a meristematic tissue called the phellogen, or cork cambium, and its derivatives: the lignosuberized phellem and the phelloderm. Research on the periderm has mainly focused on the chemical composition of the phellem due to its relevance as a raw material for industrial processes. Today, there is increasing interest in the regulatory network underlying periderm development as a novel breeding trait to improve plant resilience and to sequester CO2. Here, we discuss our current understanding of periderm formation, focusing on aspects of periderm evolution, mechanisms of periderm ontogenesis, regulatory networks underlying phellogen initiation and cork differentiation, and future challenges of periderm research. Expected final online publication date for the Annual Review of Plant Biology, Volume 73 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Distinct within-host bacterial populations ensure function, colonization and transmission in leaf symbiosis

Hereditary symbioses have the potential to drive transgenerational effects, yet the mechanisms responsible for transmission of heritable plant symbionts are still poorly understood. The leaf symbiosis between Dioscorea sansibarensis and the bacterium Orrella dioscoreae offers an appealing model system to study how heritable bacteria are transmitted to the next generation. Here, we demonstrate that inoculation of apical buds with a bacterial suspension is sufficient to colonize newly-formed leaves and propagules, and to ensure transmission to the next plant generation. Flagellar motility is not required for movement inside the plant, but is important for the colonization of new hosts. Further, stringent tissue-specific regulation of putative symbiotic functions highlight the presence of two distinct subpopulations of bacteria in the leaf gland and at the shoot meristem. We propose that bacteria in the leaf gland dedicate resources to symbiotic functions, while dividing bacteria in the shoot tip ensure successful colonization of meristematic tissue, glands and propagules. Compartmentalization of intra-host populations, together with tissue-specific regulation may serve as a robust mechanism for the maintenance of mutualism in leaf symbiosis.ImportanceSeveral plant species form associations with bacteria in their leaves, called leaf symbiosis. These associations are highly specific, but the mechanisms responsible for symbiont transmission are poorly understood. Using the association between the yam species Dioscorea sansibarensis and Orrella dioscoreae as a model leaf symbiosis, we provide experimental evidence that bacteria are transmitted vertically and distributed to specific leaf structures via association with shoot meristems. Flagellar motility is required for initial infection, but does not contribute to spread within host tissue. We also provide evidence that bacterial subpopulations at the meristem or in the symbiotic leaf gland differentially express key symbiotic genes. We argue that this separation of functional symbiont populations, coupled to tight control over bacterial infection and transmission, explain the evolutionary robustness of leaf symbiosis. These findings may provide insights into how plants may recruit and maintain beneficial symbionts at the leaf surface.

Regeneration of Dead Bougainvillea Tree with Organic Manure

Bougainvillea is hard, woody climber tree, grow in high salt tolerant soil. The present study was carried out in regenerating Bougainvillea plant with organic manure. The research work was conducted at kitchen garden campus in January 2020. The collected soil samples of five trees species namely Pimple, Neem, Khejari and Rohira are mixed with 10kg fresh cow dung, 5kg cow urine, 2kg molasses & 2kg flour Kitchen wastes 10kg, Charcoal 10kg, Molasses 2kg, Rice 1kg, Humus 10kg, Wheat 10kg, Crashed sugar cane 10kg, Chicken manures 2kg, Wooden saw dust, Wooden chips & Rice lusts and mixed with water for preparing organic product. The organic product keeps for 3 days in open conditions. The prepared organic product was poured into the shoot and root. Later, the regrowth of the shoot and the root were reported in 4-5 months. The organic product enhanced the metabolism for regenerating permanent tissue and Meristematic tissue of Shoot horizon and root horizon. Later, The lateral branches and flower were emerged from the dead plant. The formulated organic product is competent to regrow dead plant. Keywords: Bougainvillea, Dead plant, organic manure, regeneration, soil, climate

Effect of Boron Application On Growth, Yield Parameters, Nutrient Uptake, Quality and Economics of Groundnut (Arachis hypogaea L.); A Review

Groundnut is an important crop cultivated all over world owing to its versatile nature of adaptation to different agro-climatic and soil conditions. In India groundnut gains momentum as an edible oil and India next to food grain. Nutritionally groundnut contains 50 % oil, 25-30 % protein, 20% carbohydrate and 5%fiber. The productivity is lower due to different factors among which nutrient management especially boron that plays pivot role in governing the growth, yield and quality of groundnut. Boron plays various role in the physiological processes of plants, such as cell elongation, cell maturation, meristematic tissue development and protein synthesis, cellular membrane function, reproductive structures and anti- oxidative defence system. It induces flowering, fertilization, hormonal metabolism and translocation of sugars from source to sink. Extensive investigations of research on boron levels were critically reviewed. Application of boron at 10-15 kg ha-1 of soil application and foliar application of 0.5 percent at critical stage was found to increase the growth and yield attributes, yield, quality as well as higher benefit cost ratio sustaining the livelihood of groundnut growers.

Summer Heatwave Impacts on the European Kelp Saccharina latissima Across Its Latitudinal Distribution Gradient

Kelps are important foundation species in coastal ecosystems currently experiencing pronounced shifts in their distribution patterns caused by ocean warming. While some populations found at species’ warm distribution edges have been recently observed to decline, expansions of some species have been recorded at their cold distribution edges. Reduced population resilience can contribute to kelp habitat loss, hence, understanding intraspecific variations in physiological responses across a species’ latitudinal distribution is crucial for its conservation. To investigate potential local responses of the broadly distributed kelp Saccharina latissima to marine heatwaves in summer, we collected sporophytes from five locations in Europe (Spitsbergen, Bodø, Bergen, Helgoland, Locmariaquer), including populations exposed to the coldest and warmest local temperature regimes. Meristematic tissue from sporophytes was subjected to increasing temperatures of Δ+2, Δ+4 and Δ+6°C above the respective mean summer temperatures (control, Δ±0°C) characteristic for each site. Survival and corresponding physiological and biochemical traits were analyzed. Vitality (optimum quantum yield, Fv/Fm) and growth were monitored over time and biochemical responses were measured at the end of the experiment. Growth was highest in northern and lowest in southern populations. Overall, northern populations from Spitsbergen, Bodø and Bergen were largely unaffected by increasing summer temperatures up to Δ+6°C. Conversely, sporophytes from Helgoland and Locmariaquer were markedly stressed at Δ+6°C: occurrence of tissue necrosis, reduced Fv/Fm, and a significantly elevated de-epoxidation state of the xanthophyll cycle (DPS). The variations in phlorotannins, mannitol and tissue C and N contents were independent of temperature treatments and latitudinal distribution pattern. Pronounced site-specific variability in response to increasing temperatures implies that exceeding a threshold above the mean summer temperature exclusively affect rear-edge (southernmost) populations.

Green Globular Body (GGB) Induction and Differentiation in the Medicinal fern Drynaria Roosii

Background: The green globular body (GGB) of ferns is a special propagule induced in plant in vitro culture systems. Owing to its high proliferation efficiency, GGB is widely used in the in vitro propagation of important ornamental and medicinal ferns. In addition, propagation using GGB shows great development prospects in the conservation of rare or endangered ferns and the breeding of new fern varieties. However, due to the lack of systematic studies on GGB ontogenesis, the morphogenetic aspects of GGB during induction and differentiation remain unclear.Results: We characterized the response of five types of explants of Drynaria roosii to GGB inductive medium and further investigate morphological and anatomical changes of explants that developed GGBs. We found that the rhizome explants directly produced GGBs through cell proliferation of the shoot apical meristem and lateral meristem. The leaf and petiole explants produced GGBs indirectly through the proliferation of meristematic cells of somatic embryos derived from the epidermal cells of the explants. The root and gametophyte explants failed to produce GGB under our induction conditions. We further investigated the differentiation process of GGB. During GGB differentiation, shoot primordia and leaf primordia differentiate from meristematic cells on the epidermis, and the root primordia develop from an inner meristematic tissue with developing vascular tissue connecting all these primordia, which indicates the involvement of multiple organogenesis processes.Conclusions: Our results suggested that preexisting or reestablished meristematic cells were the direct source of GGB in D. roosii. Somatic embryogenesis and organogenesis were involved in GGB induction and differentiation, respectively. The comparison with other common propagules revealed that GGB in D. roosii was largely different from somatic embryos, callus, and protocorm or protocorm-like bodies.

Genetic transformation of apical meristematic shoots in the banana cultivar ‘Williams’

Bananas and plantains (Musa spp.) are among the most critical socioeconomic crops globally, being a staple food for millions of people in the tropics and an essential component for the export market, including the subtropics. Besides conventional breeding, genetic improvement of bananas and plantains could be performed through genetic engineering and new breeding techniques. Furthermore, plant tissue culture is essential for these technologies, including developing embryogenic cell suspensions and in vitro plants. The transient and stable genetic transformation could be performed from in vitro plants, shortening Musa transgenic lines development compared to genetic transformation while using embryogenic cell suspension. In this study, a genetic transformation protocol was established from banana apical meristems for the ‘Williams’ cultivar (genotype AAA). The protocol was based on the co-cultivation of the explants (whole in vitro plants or bisected meristematic tissues derived from in vitro plants) with Agrobacterium tumefaciens strain LBA4404 harboring two binary vectors denominated pLVCIBE1 (cassette: MabHIPP promoter::luc2::Tnos, P35S::hpt::Tnos) and pLVCIBE2 (cassette: P35S::luc2::Tnos, P35S::hpt::Tnos), independently. The stable genetic transformation was obtained by subculturing in vitro banana plants in selection medium (12.5µg/mL of hygromycin) for 8 weeks from bisected meristematic tissue transformation. Genetic transformation was confirmed in vivo with the use of the luciferase reporter gene system. Furthermore, PCR was performed on DNA extracted from leaves of regenerated transgenic in vitro plants after 8 weeks of selection, confirming stable genetic transformation. Therefore, genetic transformation was achieved in the apical meristematic tissue of in vitro banana plants with co-cultivation of Agrobacterium tumefaciens.

How plants minimize somatic evolution

A remarkable property of plants is their ability to accumulate mutations at a very slow pace despite their potentially long lifespans, during which they continually form buds, each with the potential to become a new branch. Because replication errors in cell division represent an unavoidable source of mutations, minimizing mutation accumulation requires the minimization of cell divisions. Here we show that there exists a well defined theoretical minimum for the branching cost, defined as the number of cell divisions necessary for the creation of each branch. Most importantly, we also show that this theoretical minimum can be closely approached by a simple pattern of cell divisions in the meristematic tissue of apical buds during the generation of novel buds. Both the optimal pattern of cell divisions and the associated branching cost are consistent with recent experimental data, suggesting that plant evolution has led to the discovery of this mechanism.

Plasma membrane vesicles from cauliflower meristematic tissue and their role in water passage

Background Cauliflower (Brassica oleracea L. var. botrytis) inflorescences are composed mainly of meristematic tissue, which has a high cellular proliferation. This considerable cellular density makes the inflorescence an organ with a large proportion of membranes. However, little is known about the specific role of the lipid and protein composition of the plasma membrane present in this organ. Results In this work, we analyzed the lipids and proteins present in plasma membrane from two different stages of development of cauliflower inflorescence and compared them with leaf plasma membrane. For this purpose, plasma membrane vesicles were obtained by centrifugation for each sample and the vesicular diameter and osmotic permeability (Pf) were analyzed by dynamic light scattering and the stopped-flow technique, respectively. In addition, fatty acids and sterols were analyzed by gas chromatography and HPLC. The protein composition of the inflorescences and leaves was characterized by HPLC-ESI-QTOF-MS and the data obtained were compared with Brassicaceae proteins present in the UniProt database in relation to the presence of aquaporins determined by western blot analysis. The highest Pf value was found in 90 day inflorescences-derived plasma membrane vesicles (61.4 ± 4.14 μms− 1). For sterols and fatty acids, the concentrations varied according to the organ of origin. The protein profile revealed the presence of aquaporins from the PIP1 and PIP2 subfamilies in both inflorescences and leaves. Conclusion This study shows that the composition of the sterols, the degree of unsaturation of the fatty acids, and the proteins present in the membranes analyzed give them high functionality for water passage. This represents an important addition to the limited information available in this field.

Polyploidy in tissues of plants in vitro of grape somaclones

In vitro experimental plants obtained by clonal micropropagation of 9 grape somaclones of 5 original forms were the material for cytogenetic research. A biological microscope XSP-146TP was used for cytogenetic analysis. 823 cases of deviation from diploidy were observed in total. Significant tissue ploidy was observed in the meristematic tissue of in vitro plants of grape somaclones obtained by colchicine treatment of proembryogenic cells of various varieties. The significant direct correlation was found between the frequency of polyploidy in meristem tissues of in vitro plants and the number of chloroplasts in the stomata of grape somaclones. The reverse correlation was found between the frequency of polyploidy and the number of stomata on the leaf area. Somaclone No. 72, obtained as a result of regeneration from colchicinated proembryogenic cells of the Ruta grape variety and identified as a tetraploid (2n = 4x = 76), is recommended for use in the polyploid creation program.