Macrophylla Seedlings Research Articles

The Impact of Culture Time on Genistin and Genistein Accumulation in Flemingia macrophylla (Willd.) Prain Seedlings and the Differentially Expressed Genes

Background Genistein and genistin are the main active constituents of Flemingia macrophylla (Willd.) Prain and the amount of active constituents in the roots varies depending on the cultivation time. The harvesting period has a great influence on its quality, and there are fewer studies on the optimal harvesting time of F. macrophylla, which is urgently needed to explore the optimal harvesting period to improve its use value. Purpose F. macrophylla (Willd.) Prain is an important medicinal plant distributed in China. This study aimed to enhance the accumulation of active ingredients genistin and genistein in F. macrophylla, and explore the mechanism of biological synthesis of these active compounds at molecular levels. Methods Transcriptome sequencing and high-performance liquid chromatography (HPLC) technology were applied to F. macrophylla tissue culture seedlings for 30 days after culturing (DAC), 45 DAC, 60 DAC, and 75 DAC. Then, gene expression, representative active substances, and important phenotypic indexes were analyzed. Results The highest fresh weight and root thickness were attained at 45 DAC, the highest plant height at 60 DAC, and the maximum rooting rate at 75 DAC. The genistin content reached the highest level at 45 DAC, and the content of genistein reached the highest level at 30 DAC. The total content of genistin and genistein achieved the maximum levels at 45 DAC. A total of 7,735 differently expressed genes (DEGs) in the three comparable groups, including T45d vs T30d, T60d vs T30d, and T60d vs T45d, were identified. Through the Kyoto Encyclopedia Genes and Genomes (KEGG) enrichment analysis of DEGs, isoflavonoid biosynthesis and phenylpropanoid biosynthesis pathways were significantly enriched in two groups, including T45d vs T30d and T60d vs T30d. A total of 41 DEGs involved in the production of isoflavones were discovered in the three groups. Conclusion The optimism culture time for the accumulation of genistein and genistin in F. macrophylla seedlings ranged from 30 to 45 days. Forty-one DEGs in the genistein and genistin synthesis pathways were found through transcriptomics analysis. This study sheds light on the biosynthesis of genistin and genistein in F. macrophylla.

First Report of Botrytis cinerea Causing Stem Rot on Hydrangea macrophylla in China.

Hydrangea (Hydrangea macrophylla), commonly referred to as big leaf hydrangea, is a species within the Hydrangeaceae family notable for its ornamental value. Characterized by its vividly colored sepals and lush, striking inflorescences, this species is globally esteemed as both a potted and landscape plant. Notably, in 2022, an alarming incidence of stem rot was observed in approximately 40% of H. macrophylla plants aged between six and twelve months within 16 greenhouses situated in Nanjing City (N 31°14', E 118°22'), Jiangsu Province, China. Initial symptoms of the disease manifested as wet gray-black spots at the base of the seedlings and stems, progressing to a necrotic gray-white discoloration in the stems and accompanied by the growth of gray mold on the affected parts. This infection ultimately led to the wilting of the leaves and the death of the seedlings. For pathogen identification, stem tissues at the interface of diseased and healthy sections were excised, surface-sterilized with 75 % ethanol for 30 s, followed by a 2 - 3 min treatment with 3% sodium hypochlorite, and subsequently rinsed three times with sterile water before air drying. Sections measuring 2 - 3 mm were then cultured on potato dextrose agar (PDA) medium, supplemented with 50 mg/mL rifampicin (RFP), and incubated at 25 ℃ for 3 - 5 d (Zhou et al. 2022). Upon 2 - 3 days of incubation, notable growth of fungal colonies was observed. Mycelial clusters from the periphery of these colonies were subsequently transferred to fresh PDA plates and incubated at 25 ℃ for an additional 5 - 7 d. A particular colony, designated JSNJ2022-2 and now preserved at the Jiangsu Academy of Agricultural Sciences, was selected for detailed examination. This colony exhibited a flocculent texture, with a coloration ranging from grey-white to light brown. It was characterized by the presence of irregularly formed, hard sclerotia within the hyphae. The conidiophores were observed to be slender and erect, featuring dendritic branches at their extremities. The conidia were clustered on the conidiophore like grapes. These conidia were generally colorless or grey, oval in shape, smooth and transparent, and measured between 6.4 - 12.2 × 7.3 - 18.2 μm (n = 50). For genetic analysis, genomic DNA (gDNA) was extracted using the DNA secure Plant Kit (Tiangen Biotech, Beijing, China). Polymerase chain reaction (PCR) amplification was performed using a set of universal primers of ITS1/ITS4 (White et al. 1990), primers corresponding to the specific sequences of glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) (Yang et al. 2020). The resultant PCR products were sequenced, and the resulting sequences were submitted to the GenBank database, under the accession numbers OP131597, OP142320, OP142321, and OP142322, respectively. BLAST analysis of the sequences obtained from the isolate JSNJ2022-2 revealed a high degree of genetic similarity, ranging from 99 to 100%, with known sequences of Botrytis cinerea (accessions MK051124.1, MH796662.1, MH479931.1, and KU760986.1). To elucidate the phylogenetic position of the isolate, a phylogenetic tree was constructed using the maximum likelihood method, supported by 1,000 bootstrap replications, in the Mega7 software (Kumar et al. 2016). The results of this analysis confirmed that the strains under study clustered within the same branch as B. cinerea. To establish the pathogenicity of the isolate, Koch's postulates (Falkow 1988) were employed. Healthy potted H. macrophylla seedlings, approximately three months old, were wound inoculated at the base of the seedlings with a 6 mm diameter mycelium plug of JSNJ2002-2 cultivated on PDA for 3 days, which was subsequently covered with moistened degreasing cotton. Control plants were treated with moistened degreasing cloths minus the pathogen. Post-inoculation, these plants were placed in a growth chamber maintained at 25 ℃ with a relative humidity range of 60 - 80%. After a 3-d incubation period, the inoculated plants displayed symptoms identical to those initially observed in the greenhouse. The pathogen was successfully re-isolated from these inoculated plants and was morphologically re-confirmed as B. cinerea, thus satisfying the criteria of Koch's postulates. To our knowledge, this report represents the first documented incidence of B. cinerea causing stem rot in H. macrophylla in China.

A Transmission Assay of 'Candidatus Liberibacter asiaticus' Using Citrus Phloem Sap and Topical Feeding to Its Insect Vector, Diaphorina citri.

'Candidatus Liberibacter asiaticus', the putative causal agent of citrus greening disease, is transmitted by the Asian citrus psyllid, Diaphorina citri, in a propagative, circulative, and persistent manner. Unfortunately, 'Ca. L. asiaticus' is not yet available in pure culture to carry out Koch's postulates and to confirm its etiology. When a pure culture is available, an assay to test its infectivity in both the insect vector and the plant host will be crucial. Herein, we described a transmission assay based on the use of phloem sap extracted from infected citrus plants and topical feeding to D. citri nymphs. Phloem sap was collected by centrifugation, diluted with 0.1 M phosphate buffer pH 7.4 containing 20% (wt/vol) sucrose and 0.1% ascorbic acid (wt/vol) as an antioxidant, and delivered to third through fifth instar nymphs by placing droplets on the mouthparts. Nymphs unfolded the stylets and acquired the phloem sap containing the bacterial pathogen. Nymphs were then placed onto Citrus macrophylla seedlings (10 nymphs per seedling) for an inoculation period of 2 weeks. A transmission rate of up to 80% was recorded at 6 months postinoculation. The method could be a powerful tool to test the transmissibility of the bacterial pathogen after various treatments to reduce the viability of the bacteria or to block its transmission. In addition, it might be a potent assay to achieve Koch's postulates if a pure culture of 'Ca. L. asiaticus' becomes available.

Suhu dan Masa Simpan Benih Memengaruhi Viabilitas Benih Mahoni (Swietenia macrophylla King.)

Swietenia macrophylla or big-leaf mahogany is an exotic species from Central and South America. This tree has various benefits, so it’s used as an industrial plantation forest and afforestation in Indonesia. However, seed storage of mahogany is a major problem in cultivation, because it can reduce seed viability. The storability of seeds is influenced by seed and environmental conditions. Therefore, this study aimed to examine the effect of temperature and storage time on the viability of S. macrophylla seeds and to calculate the Seedling Quality Index (SQI). The experiment was carried out using a factorial Randomized Block Design (RBD) with 2 factors. The first factor was consisted of four levels of temperature treatment, namely room temperature (24), 4, 0, and -20°C. The second factor was the storage period treatment which consisted of 4 levels, namely 1 up to 4 weeks, with 1-week intervals. The results showed that the interaction between temperature and storage time affected mahogany leaves, primary and secondary roots, root/shoot ratio, and total wet weight of S. macrophylla seedlings. Mahogany seeds that were stored at room temperature for 1 week resulted in the highest seed viability, with SQI of 0.03-0.04.

Transcriptome and metabolome analysis reveals mechanism of light intensity modulating iridoid biosynthesis in Gentiana macrophylla Pall.

Light intensity is a key factor affecting the synthesis of secondary metabolites in plants. However, the response mechanisms of metabolites and genes in Gentiana macrophylla under different light intensities have not been determined. In the present study, G. macrophylla seedlings were treated with LED light intensities of 15 µmol/m2/s (low light, LL), 90 µmol/m2/s (medium light, ML), and 200 µmol/m2/s (high light, HL), and leaves were collected on the 5th day for further investigation. A total of 2162 metabolites were detected, in which, the most abundant metabolites were identified as flavonoids, carbohydrates, terpenoids and amino acids. A total of 3313 and 613 differentially expressed genes (DEGs) were identified in the LL and HL groups compared with the ML group, respectively, mainly enriched in KEGG pathways such as carotenoid biosynthesis, carbon metabolism, glycolysis/gluconeogenesis, amino acids biosynthesis, plant MAPK pathway and plant hormone signaling. Besides, the transcription factors of GmMYB5 and GmbHLH20 were determined to be significantly correlated with loganic acid biosynthesis; the expression of photosystem-related enzyme genes was altered under different light intensities, regulating the expression of enzyme genes involved in the carotenoid, chlorophyll, glycolysis and amino acids pathway, then affecting their metabolic biosynthesis. As a result, low light inhibited photosynthesis, delayed glycolysis, thus, increased certain amino acids and decreased loganic acid production, while high light got an opposite trend. Our research contributed significantly to understand the molecular mechanism of light intensity in controlling metabolic accumulation in G. macrophylla.

Integrated physiological, transcriptomic, and metabolomic analyses of drought stress alleviation in Ehretia macrophylla Wall. seedlings by SiO2 NPs (silica nanoparticles).

With environmental problems such as climate global warming, drought has become one of the major stress factors, because it severely affects the plant growth and development. Silicon dioxide nanoparticles (SiO2 NPs) are crucial for mitigating abiotic stresses suffered by plants in unfavorable environmental conditions and further promoting plant growth, such as drought. This study aimed to investigate the effect of different concentrations of SiO2 NPs on the growth of the Ehretia macrophylla Wall. seedlings under severe drought stress (water content in soil, 30-35%). The treatment was started by starting spraying different concentrations of SiO2 NPs on seedlings of Ehretia macrophyla, which were consistently under normal and severe drought conditions (soil moisture content 30-35%), respectively, at the seedling stage, followed by physiological and biochemical measurements, transcriptomics and metabolomics analyses. SiO2 NPs (100 mg·L-1) treatment reduced malondialdehyde and hydrogen peroxide content and enhanced the activity of antioxidant enzymes under drought stress. Transcriptomic analysis showed that 1451 differentially expressed genes (DEGs) in the leaves of E. macrophylla seedlings were regulated by SiO2 NPs under drought stress, and these genes mainly participate in auxin signal transduction and mitogen-activated protein kinase signaling pathways. This study also found that the metabolism of fatty acids and α-linolenic acids may play a key role in the enhancement of drought tolerance in SiO2 NP-treated E. macrophylla seedlings. Metabolomics studies indicated that the accumulation level of secondary metabolites related to drought tolerance was higher after SiO2 NPs treatment. This study revealed insights into the physiological mechanisms induced by SiO2 NPs for enhancing the drought tolerance of plants.

Genomic characterization of WRKY transcription factors related to secoiridoid biosynthesis in Gentiana macrophylla

Gentiana macrophylla is one of Chinese herbal medicines in which 4 kinds of iridoids or secoiridoids, such as loganic acid, sweroside, swertiamarin, and gentiopicroside, are identified as the dominant medicinal secondary metabolites. WRKY, as a large family of transcription factors (TFs), plays an important role in the synthesis of secondary metabolites in plants. Therefore, WRKY genes involved in the biosynthesis of secoiridoids in G. macrophylla were systematically studied. First, a comprehensive genome-wide analysis was performed, and 42 GmWRKY genes were identified, which were unevenly distributed in 12 chromosomes. Accordingly, gene structure, collinearity, sequence alignment, phylogenetic, conserved motif and promoter analyses were performed, and the GmWRKY proteins were divided into three subfamilies based on phylogenetic and multiple sequence alignment analyses. Moreover, the enzyme-encoding genes of the secoiridoid biosynthesis pathway and their promoters were then analysed, and the contents of the four secoiridoids were determined in different tissues. Accordingly, correlation analysis was performed using Pearson′s correlation coefficient to construct WRKY gene-enzyme-encoding genes and WRKY gene–metabolite networks. Meanwhile, G. macrophylla seedlings were treated with methyl jasmonate (MeJA) to detect the dynamic change trend of GmWRKYs, biosynthetic genes, and medicinal ingredient accumulation. Thus, a total of 12 GmWRKYs were identified to be involved in the biosynthesis of secoiridoids, of which 8 (GmWRKY1, 6, 12, 17, 33, 34, 38 and 39) were found to regulate the synthesis of gentiopicroside, and 4 (GmWRKY7, 14, 26 and 41) were found to regulate the synthesis of loganic acid. Taken together, this study systematically identified WRKY transcription factors related to the biosynthesis of secoiridoids in G. macrophylla, which could be used as a cue for further investigation of WRKY gene functions in secondary metabolite accumulation.

The growth of mahogany seedlings (Swietenia macrophylla King.) in various planting media and shade intensity

Swietenia macrophylla has potential in the economic, health and environmental sectors; so, this tree is one of the species used for forest rehabilitation. The growth of S. macrophylla is influenced by environmental factors, including the quality of the growing medium and shade intensity. This study aimed to obtain the right planting medium and shade for the growth of S. macrophylla seedlings. This research was conducted using a split-plot design with randomized groups. The main plot was shade using paranet which consists of 2 levels, while the subplot was the planting medium which consists of 5 levels. The results showed that the interaction of mineral soil medium treatment and without shade resulted in the highest seedlings height and total fresh weight in mahogany seedlings. The quality index of mahogany seedlings (SQI) is influenced by no-shade treatment

Effects of tree species diversity and conspecific seedling density on insect herbivory and pathogen infection on big‐leaf mahogany seedlings

The Janzen–Connell hypothesis (JCH) predicts that attack by specialist enemies on seedlings increases with conspecific seedling density, but studies have rarely experimentally tested for the contingency of such effects on the tree community context (e.g. diversity, composition) ormeasured responses by different enemies (e.g. herbivores, pathogens). We conducted a field study in a large‐scale system evaluating tree species diversity and conspecific density effects on leaf damage on mahogany Swietenia macrophylla seedlings. We established quadrats of eight levels of seedling density across mahogany tree monocultures and tree species polycultures including mahogany, and recorded percent leaf damage by insects and percent leaf necrosis by a pathogenic fungus on mahogany seedlings. We found contrasting effects of tree species diversity on insects and pathogens. Whereas tree diversity did not affect leaf damage by insects, it had a significant negative effect on leaf necrosis by pathogens whereby, on average, percent leaf necrosis on mahogany seedlings in polyculture was half of that observed in monoculture. We discuss the potential influences of changes in mahogany tree density versus frequency (relative to other tree species) driving this diversity effect. Unexpectedly, we found no effect of seedling conspecific density on either leaf insect or pathogen damage (i.e. density‐independent attack). Likewise, we found no significant tree diversity by seedling density interaction, indicating that plant enemies were consistently unresponsive to variation in seedling density acrosslevels of tree diversity. Overall, this study provides a unique test of the JCH by experimentally evaluating seedling density and tree diversity effects on contrasting plant enemies and, in turn, the controls they exert over plant recruitment.

Growth response of three forest seedlings to iron exposure

Fe is one of the microessential plants needed in low concentrations. The purpose of this study was to examine the growth response of three forest seedlings to iron exposure in water culture media. This study used a completely randomized design (CRD) with Fe dose treatment and consisted of 9 levels, namely 0, 0.5, 0.1, 1.5, and 2, with 3 replications each and each replication consisting of 3 plant units. The plants used consisted of Ochroma bicolor, Shorea macrophylla, and Senna siamea. The results of this study showed that Fe exposure treatment had a significant effect on the three seedlings on all growth parameters (height, root length, root dry weight, shoots, and total dry weight). Increasing the concentration of Fe can reduce all growth parameters. The three seedlings have different tolerance levels. Fe exposure treatment had a significant effect on the SPAD index only on O. bicolor and S. seamea seedlings. S. macrophylla seedlings had the highest tolerance index value compared to the other two seedlings. This indicated that S. macrophylla seedlings had higher resistance than the other two seedlings to Fe exposure.

Outplanting Performance of the Bornean Tropical Indigenous Species Shorea macrophylla (de Vriese) P. S. Ashton in relation to Seedling Age

Planting high-quality seedlings with desirable growth attributes are associated with successful survival and growth performance following outplanting. Considering that most tree species from the Dipterocarpaceae family are on the IUCN Red List of Threatened Species, proper conservation of such species is necessary. Very little is known with no clear consensus regarding whether increasing the seedling production period enhances outplanting survival and growth potential of tropical dipterocarp species planted under enrichment planting in Malaysia. In this study, one potential Bornean tropical indigenous species, Shorea macrophylla (de Vriese) P.S. Ashton, was produced in the Universiti Malaysia Sarawak nursery and outplanted at Sampadi Forest Reserve, Sarawak. Different nursery production periods (3, 6, 9, and 24 months) were tested for the species at the time of planting as well as for the subsequent growth performance after 12, 24, and 42 months of outplanting. The findings revealed that older (9- and 24-month-old) S. macrophylla seedlings were morphologically larger from younger (3- and 6-month-old) seedlings. Nonetheless, the overall pooled mean survival rates declined from 61.7 to 44.6% after 12, 24, and 42 months of outplanting. For the 42-month period, the survival rate for the 9-month-old seedlings was significantly higher than that for the 3-, 6-, and 24-month-old seedlings. Notwithstanding, the relative growth rate of the stem diameter was higher for the 3- and 9-month-old seedlings than for the 6- and 24-month-old seedlings after 42 months of outplanting. Thus, maintaining plant material from the seedlings produced at 3, 6, and 9 months of age would be beneficial for the initiation of transplantation in restoration programmes in Sarawak. The 24-month-old seedlings will also be useful, especially during irregular flowering and unpredictable fruiting intervals. A further experimental study on other environmental factors that could influence the outplanting performance of the seedlings in the tropical forest restoration area of Sarawak, Malaysia, is necessary.

Ammonium supply enhances growth and phosphorus uptake of mahogany (Swietenia macrophylla) seedlings compared to nitrate

Nitrogen (N) is the mineral nutrient required in greater quantities by plants with deficiencies affecting crop production. Nitrate (NO3 -) and ammonium (NH4 +) are the inorganic N forms most readily available for plant uptake. We investigated the influence of ammonium and nitrate rates on growth, nutritional status, chlorophyll production, and nutritional efficiency in mahogany seedlings, grown in an Oxisol soil under greenhouse conditions. Treatments were five N rates (50, 100, 150, 200, and 400 mg dm−3 N) in ammonium and nitrate forms and control treatment (0 mg dm−3 N), in a factorial design with five replications. The plants were harvested for evaluation at 150 days after transplanting. N supply affected mahogany growth, mainly in the production of leaf tissue. The maximum economic efficiency of N rates for production of leaf tissue was around 190 mg dm−3 N. The ammonium supply enhanced leaf tissue production, with a 20% increase in leaf area and 15% in leaf dry matter compared to nitrate. Furthermore, the plants showed a preference for ammonium uptake in rates above 200 mg dm−3 N, which indicates that the preference for N form was dependent on the concentration of N in the soil. The ammonium supply enhanced nutritional status, mainly phosphorus, demonstrating high synergism on uptake of this nutrient. Conversely, a strong antagonism between nitrate and phosphorus uptake was observed. Thus, ammonium enhanced the growth and nutritional status of mahogany seedlings and must be prioritized in its fertilization.

Afforestation in barren laterite lands with Swietenia macrophylla G. King and plant growth promoting microbes

Barren laterite lands are available plenty in Kasargode District of Kerala, India and being used mainly for extracting laterite bricks for building construction. These lands are found barren due to lack of vegetation and rocky nature. Afforestation in these lands is very essential to avoid extraction of laterite bricks so as to prevent degradation of lands. To develop vegetation in these laterite lands the soil properties of laterite was examined as a first step of afforestation process. It was found that the soils have lack of plant growth promoting microbes (PGPM) and poor in major nutrients (N, P, K). Therefore, the PGPM specifically arbuscular mycorrhizal fungi (Glomus fasciculatum and Glomus geosporum) and bacteria (Azospirillum brasilense and Bacillus megaterium) were used for afforestation in laterite lands along with Swietenia macrophylla G. King a commercially important tree of Kerala, India. The laterite soils were collected and used as potting media for growing seedlings of S. macrophylla in nursery and the cultured PGPM were inoculated in to the seedlings of S. macrophylla and maintained for 3 months. The PGPM inoculated seedlings showed improved growth, biomass and nutrient uptake. Thereafter the seedlings were transplanted at laterite lands at Karmanthodi, Bovikanam, Kasargode, Kerala, India and monitored their growth for 12 months. The seedlings inoculated with PGPM showed up to 98% survival rate with improved growth. From this study it was understood that PGPM have the potential to increase the efficiency of plant growth system in S. macrophylla seedlings through supply of essential levels of N, P and K that helped for successful afforestation in hardy laterite lands.

Influences of inorganic and organic fertilizers to morphological quality attributes of Shorea macrophylla seedlings in a tropical nursery

Abstract. Perumal M, Wasli ME, Ho SY. 2019. Influences of inorganic and organic fertilizers to morphological quality attributes of Shorea macrophylla seedlings in a tropical nursery. Biodiversitas 20: 2110-2118. Better understanding and implementation of nursery cultural regimes to improve seedling quality with high survival capability and optimal growth potential are one of the pivotal aspects of a successful forest restoration program. An experiment was set to determine the influences of inorganic and organic fertilizers on the morphological quality attributes of Shorea macrophylla (de Vriese) P.S. Ashton seedlings. For seedling production, the pots were filled with a 1:1 mixture of topsoil and sand (v:v), following the standard forest nursery practice. Either a chemical fertilizer (CF, N: P: K = 10: 26: 10) or a blend of 360-day (80% elution of the ingredients at 25°C) controlled-instant release fertilizer (CIRF, N: P: K = 10: 26: 10) or a jellyfish fertilizer (JF, N: P: K = 13.1: 1.7: 0.03) was applied at the rate of 5 g per pot. The findings revealed that the morphological quality attributes of S. macrophylla seedlings treated with JF were significantly higher (P < 0.05) than the seedlings treated with CF and CIRF at the end of nursery growing season. Notwithstanding, in terms of seedling quality indicators, seedlings from all the treatments were fit to the general expectations of a balanced root to shoot ratio values (RS < 2) and the seedlings raised in the nursery were of sub-optimal quality. Consequently, stock quality evaluation requires the integration of both morphological and physiological attributes of seedlings that provides a more effective appraisal of the fitness of seedlings to become established for field planting.

Prolonged drying cycles stimulate ABA accumulation in Citrus macrophylla seedlings exposed to partial rootzone drying

Partial rootzone drying (PRD) establishes discrete wet and dry parts of the rootzone (for example using parallel drip lines on either side of the crop row), and alternates them to stimulate root growth and root-to-shoot ABA signalling. To assess whether alternation frequency affects plant physiological responses, Citrus macrophylla Wester seedlings were grown with the root system split between two pots and 5 irrigation treatments applied: Control, PRD-Fixed (where wet and dry parts of the rootzone were not alternated) and three alternate PRD treatments where the wet and dry parts were swapped at 3 (PRD1), 6 (PRD2) and 12 (PRD3) days intervals, to dry the soil to different degrees before alternating the irrigation. Water was equally distributed between both pots in Control plants, whereas only one pot was watered and the other allowed to dry in PRD plants, with all plants receiving the same irrigation volume. After 24 days, soil water content (θv), leaf water potential (Ψleaf), root water potential (Ψroot), abscisic acid (ABA) concentration in roots ([ABA]root), leaves ([ABA]leaf) and shoot xylem sap ([X-ABA]shoot), biomass allocation and leaf area were measured. Higher soil water availability of the dry side (PRD1 and PRD2) had no significant effects on leaf water relations, ABA status and plant biomass allocation. However, increasing the duration of exposure of part of the root system to dry soil (PRD3 and PRD-Fixed) further decreased Ψroot and stimulated root ABA accumulation, while decreasing Ψleaf and increasing [ABA]leaf of PRD3 plants compared to the other treatments. Differences in physiological response between PRD3 and PRD-Fixed plants were attributed to differences in the proportion of root mass exposed to drying soil: PRD3 plants had a lower Ψleaf and a higher [ABA]leaf with a smaller proportion of their root mass in wet soil. Since long drying cycles were required to alter plant biomass allocation and physiological responses in PRD plants, these should be implemented in designing suitable PRD strategies for field application.

Dasistoma macrophylla: Hemiparasite growth and impact onAcer saccharumandQuercus macrocarpa

Abstract Dasistoma macrophylla (Nutt.) Raf. is a photosynthetically competent hemiparasitic plant known to parasitize 21 different tree species. How different tree species vary in quality as hosts for this hemiparasite and how parasitism affects host growth have not been explored. We tested the hypothesis that D. macrophylla form more vascular connections, known as haustoria, to roots of the tree species that promotes greater growth of the hemiparasite in a greenhouse experiment. Juvenile Acer saccharum Marshall (sugar maple), a known host, and Quercus macrocarpa Michx. (bur oak), a previously untested species common to the locality, were grown alone or with one seedling of D. macrophylla derived from one of two populations. Additional D. macrophylla seedlings were grown alone. After 17 wk, dry shoot and root mass of the tree, dry shoot, and root mass of the hemiparasite, and the number of haustoria formed by the hemiparasite were determined. Dasistoma macrocarpa grew better with A. saccharum than it did ...

Remnant Trees in Enrichment Planted Gaps in Quintana Roo, Mexico: Reasons for Retention and Effects on Seedlings

Natural forest management in the tropics is often impeded by scarcity of advanced regeneration of commercial species. To supplement natural regeneration in a forest managed by a community in the Selva Maya of Mexico, nursery-grown Swietenia macrophylla seedlings were planted in multiple-tree felling gaps, known as bosquetes. Remnant trees are often left standing in gaps for cultural and economic reasons or due to their official protected status. We focus on these purposefully retained trees and their impacts on planted seedlings. Sampled bosquetes were 400–1800 m2, of which remnant trees covered a mean of 29%. Seedling height growth rates over the first 18 months after out-planting more than doubled with increased canopy openness from 0.09 m year−1 under medium cover to 0.22 m year−1 in full sun. Liana infestations and shoot tip damage were most frequent on seedlings in the open, but, contrary to our expectations, height growth rates were 0.14 m year−1 faster for liana-infested seedlings than non-infested and did not differ between damaged and undamaged seedlings. Apparently the more rapid height growth of well-illuminated seedlings more than compensated for the effects of lianas or shoot tip damage. Despite the abundance of remnant trees and their negative effects on seedling growth, enrichment planting in bosquetes has potential for community-based natural forest management in the tropics in supplementing natural regeneration of commercial species. One obvious recommendation is to leave fewer remnant trees, especially those of commercial species that are non-merchantable due to stem defects and trees retained for no apparent reason, which together constituted half of the remnant crown cover in the sampled bosquetes. Finally, given the rapid growth of lianas and understory palms in large canopy gaps, at least the most vigorous of the planted seedlings should be tended for at least two years.

Emergência e crescimento inicial de plântulas de Swietenia macrophylla (King) em função da posição da semente e presença do endocarpo

Mahogany (Swietenia macrophylla King) is a high economic potential Meliaceae found in an upland forest of the Brazilian Amazon, one of the most exploited species in Brazil and because of that is endangered. The study aimed to evaluate the effect of sowing position and presence of endocarp in the emergence and initial growth of S. macrophylla seedlings. The design was completely randomized with four replications of 25 seeds, arranged in a factorial 3 × 2 (positions and endocarp). The treatments consisted of different positions of the seed on the substrate with reference to the germ pore: 0° – germ pore turned up – PGC; 90° – germ pore turned to the side – PGL; 180° – germ pore turned down – PGB. Were evaluated: the percentage of emergency, emergency mean time, stem diameter, number of leaves, shoot height, root length, dry weight of shoot and root dry mass. The seed positions affect the percentage and the mean time of seedlings emergency of S. macrophylla. The position 0o provides greater emergence rates and lower mean time of emergency. To encourage the emergence and initial growth of S. macrophylla seedlings, sowing should be performed with the seed germination pore turned up without the presence of endocarp.

Transcriptional Responses and Gentiopicroside Biosynthesis in Methyl Jasmonate-Treated Gentiana macrophylla Seedlings.

Gentiana macrophylla, a medicinal plant with significant pharmacological properties, contains the bioactive compound gentiopicroside. Methyl jasmonate (MeJA) is an effective elicitor for enhancing the production of such compounds. However, little is known about MeJA-mediated biosynthesis of gentiopicroside. We investigated this phenomenon as well as gene expression profiles to determine the molecular mechanisms for MeJA-mediated gentiopicroside biosynthesis and regulation in G. macrophylla. Our HPLC results showed that Gentiana macrophylla seedlings exposed to MeJA had significantly higher concentrations of gentiopicroside when compared with control plants. We used RNA sequencing to compare transcriptional profiles in seedlings treated for 5 d with either 0 μmol L-1 MeJA (C) or 250 μmol L-1 MeJA (M5) and detected differentially expressed genes (DEGs). In total, 77,482 unique sequences were obtained from approximately 34 million reads. Of these, 48,466 (57.46%) sequences were annotated based on BLASTs performed against public databases. We identified 5,206 DEGs between the C and M5 samples, including genes related to the α-lenolenic acid degradation pathway, JA signaling pathway, and gentiopicroside biosynthesis. Expression of numerous enzyme genes in the glycolysis pathway was significantly up-regulated. Many genes encoding transcription factors (e.g. ERF, bHLH, MYB, and WRKY) also responded to MeJA elicitation. Rapid acceleration of the glycolysis pathway that supplies precursors for IPP biosynthesis and up-regulates the expression of enzyme genes in that IPP pathway are probably most responsible for MeJA stimulation of gentiopicroside synthesis. Our qRT-PCR results showed that the expression profiles of 12 gentiopicroside biosynthesis genes were consistent with the RNA-Seq data. These results increase our understanding about how the gentiopicroside biosynthesis pathway in G. macrophylla responds to MeJA.

Soilless Nursery Media for African Oil Bean (Pentaclethra macrophylla Benth) Seedling Production

African oil bean (Pentaclethra macrophylla) is an important multi-purpose tree crop. However, bottleneck in seedling production to fully domesticate this crop has not been resolved. This study was carried out to compare the effect of three different soilless media on the production of Pentaclethra macrophylla seedlings. The experiment was laid out in a completely randomized design (crd) with 10 replications using potting bags (25 x 23 cm) filled with the treatments namely sawdust + poultry manure (sd+pm) 3:1 volume by volume (v/v), rice hull + poultry manure (rh +pm) 3:1 v/v, and groundnut husk + poultry manure (gh + pm) 3:1 v/v. Top soil served as the control. Germination and plant growth parameters were studied; days to emergence, germination count (%), plant height and number of leaves at 30, 40, 50, 60 and 70 days after planting (dap). Original Research Article Onwubiko et al.; IJPSS, 5(3): 186-190, 2015; Article no.IJPSS.2015.072 187 Germination count (%) was recorded highest on sd + pm while gh + pm had the least. This study suggests the use of sd + pm for seedling production.