Effects of nitrogen and phosphorus availability on the early growth of two congeneric pairs of savanna and forest species

In the tropical region, savannas and seasonal forests, both highly diverse biomes, occur side by side, under the same climate. If so, that mosaic cannot be explained solely by climatic variables, but also by fire, water availability and soil status. Nutrient availability in the soil, especially nitrogen and phosphorus, has been postulated to explain the abrupt transitions between savannas and seasonal forests in tropical regions. Plants from these two biomes may present different nutritional strategies to cope with nitrogen and phosphorus limitation. We used two congeneric pairs of trees — each pair with a species from the savanna and another from the neighboring seasonal forest — to test whether savanna and forest species presented different nutritional strategies during their early development. We cultivated 56 individuals from each of these species in a hydroponics system with four treatments: (1) complete Hoagland solution, (2) Hoagland solution without nitrogen, (3) Hoagland solution without phosphorus, and (4) Hoagland solution without nitrogen and phosphorus. After 45 days, we harvested the plants and measured total biomass, root to shoot ratio, height, leaf area, and specific leaf area. Overall, savanna species were lighter, shorter, with smaller leaves, higher specific leaf areas, and higher root to shoot ratios when compared to the forest species. Nitrogen increased the performance of species from both biomes. Phosphorus improved the performance of the forest species and caused toxicity symptoms in the savanna species. Hence, savanna and forest species presented different demands and were partially distinct already as seedlings concerning their nutritional strategies.

Producing Black Pepper (Piper Nigrum L. cv. ‘Kuching’) Rootstock in a Deep-Water Culture Hydroponic System

Stem cutting is the common planting material for black pepper (Piper nigrum L.) farmers mainly because the method is cheap, easy to obtain, and produces satisfactory number of new plantlets, which are relatively genetically uniform to their parent. However, soil propagation of stem cuttings renders both the stem and developing roots susceptible to soil borne pathogens, ultimately compromising the quality of the plant. Good quality rootstock of the new plant promotes faster, safer, and better black pepper plant establishment. Hydroponic farming thus offers a good platform for producing quality rootstock of the new plants and has gained importance to many farmers due to its flexibility in manipulating plant growth conditions and timely pathogen management, thus safer, healthier, and faster growth. This study investigated the growing media suitable for rootstock growth of P. nigrum L. cv. ‘Kuching’ and compared the rooting ability between stem cuttings with adventitious roots at the time of planting and stem cuttings without any root at the time of planting. In a laboratory setting, a total of 210 stem cuttings were hydroponically planted in seven nutrient compositions, with each nutrient composition containing an equal number of stem cuttings with adventitious roots at the time of planting and stem cuttings without any root at the time of planting. Hoagland solution supplemented with 0.005 mM potassium silicate solution (T4) and Hoagland solution supplemented with 2 mM salicylic acid solution (T6) showed faster root initiation whereas T1 (Hoagland solution only) produced the highest increment in root length followed by T6. The least suitable nutrient composition was T5 [T4 + 6 mL of 1 M Ca (NO3)2.4H2O solution]. The total number of roots was highest in plants from stem cuttings which had some adventitious roots at the time of planting, whereas roots in plants from stem cuttings which did not have any root at the time of planting, increased in root length faster than plants withstem cuttings which had adventitious roots at the time of planting.

Computer-Based Tools Unmask Critical Mineral Nutrient Interactions in Hoagland Solution for Healthy Kiwiberry Plant Acclimatization

The aim of this study was to better understand the response of ex vitro acclimatized plants grown to a set of mineral nutrient combinations based on Hoagland solution. To reach that, two computer-based tools were used: the design of experiments (DOE) and a hybrid artificial intelligence technology that combines artificial neural networks with fuzzy logic. DOE was employed to create a five-dimensional IV-design space by categorizing all macroelements and one microelement (copper) of Hoagland mineral solution, reducing the experimental design space from 243 (35) to 19 treatments. Typical growth parameters included hardening efficiency (Hard), newly formed shoot length (SL), total leaf number (TLN), leaf chlorophyll content (LCC), and leaf area (LA). Moreover, three physiological disorders, namely, leaf necrosis (LN), leaf spot (LS), and curled leaf (CL), were evaluated for each treatment (mineral formulation). All the growth parameters plus LN were successfully modeled using neuro-fuzzy logic with a high train set R2 between experimental and predicted values (72.67 < R2 < 98.79). The model deciphered new insights using different sets of “IF–THEN” rules, pinpointing the positive role of Mg2+ and Ca2+ to improve Hard, SL, TLN, and LA and alleviate LN but with opposite influences on LCC. On the contrary, TLN and LCC were negatively affected by the addition of NO3– into the media, while NH4+ in complex interaction with Cu2+ or Mg2+ positively enhanced SL, TLN, LCC, and LA. In our opinion, the approach and results achieved in this work are extremely fruitful to understand the effect of Hoagland mineral nutrients on the healthy growth of ex vitro acclimatized plants, through identifying key factors, which favor growth and limit physiological abnormalities.

Interactions between Indigenous Endophyte Bacillus subtilis L1-21 and Nutrients inside Citrus in Reducing Huanglongbing Pathogen Candidatus Liberibacter Asiaticus

Huanglongbing (HLB) pathogen Candidatus Liberibacter asiaticus (CLas) brings a great concern about the phloem nutrient transport in diseased plants. There is an urgent need to find the best management strategies to reduce the losses in the citrus industry worldwide. Endophytic bacteria are negatively affected by CLas pathogen, and these endophytes are associated with improved availability of nutrients and pathogen resistance. This study underpins the relationship between CLas pathogen, endophyte population and nutrients availability in citrus plants. The citrus plants were treated with Bacillus subtilis L1-21 and Hoagland solution to find out synergism efficacy to mitigate citrus HLB. We showed that citrus shoots in the presence of 50% Hoagland solution displayed maximum number of endophytes with 6.28 × 103 to 3.04 × 105 CFU/g. Among 50 candidate strains, B. subtilis L1-21 emerged as potential antagonist against surrogate strain Xanthomonas citri subsp. citri. The citrus half-leaf method identified that application of endophyte L1-21 with 50% Hoagland solution successfully reduces the CLas abundance. We point out that this combination results in a higher number of endophytes population with 2.52 × 104 to 9.11 × 106 CFU/g after 60 days, and reduces CLas pathogen abundance in asymptomatic HLB plants. In HLB symptomatic citrus plants, B. subtilis L1-21 potentially increases the endophyte population from 1.11 × 104 to 5.26 × 107 CFU/g in the presence of Hoagland solution, and pathogen abundance was reduced from 9.51 × 105 to 1.06 × 104 copies/g. Altogether, we suggested that the presence of endophyte L1-21 with Hoagland solution is more effective in HLB asymptomatic citrus plants, but a slight reduction of pathogen was observed in symptomatic plants. The findings revealed the role of indigenous citrus endophyte B. subtilis L1-21 along with other nutrients in the reduction of CLas pathogen abundance inside symptomatic and asymptomatic plants in citrus endophyte–nutrient–pathogen interplay.

Sand Particle Size and Phosphorus Amount Affect Rhizophagus irregularis Spore Production Using In Vitro Propagated Spore as a Starter Inoculum in Rhizosphere of Maize (Zea mays) Plantlets

Microbial inoculants, particularly arbuscular mycorrhizal (AM) fungi, have great potential for sustainable crop management. In this study, monoxenic culture of indigenous R. irregularis was developed and used as a tool to determine the minimum phosphorus (P) level for maximum spore production under the in vitro conditions. This type of starter AM fungal inoculum was then applied to an in vivo substrate-based mass-cultivation system. Spore production, colonization rate, and plant growth were examined in maize (Zea mays L.) plant inoculated with the monoxenic culture of R. irregularis in sand graded by particle size with varying P levels in nutrient treatments. In the in vitro culture, the growth medium supplemented with 20 µM P generated the maximum number of spores (400 spores/mL media) of R. irregularis. In the in vivo system, the highest sporulation (≈500 spores g−1 sand) occurred when we added a half-strength Hoagland solution (20 µM P) in the sand with particle size between 500 µm and 710 µm and omitted P after seven weeks. However, the highest colonization occurred when we added a half-strength Hoagland solution in the sand with particle sizes between 710 µm and 1000 µm and omitted P after seven weeks. This study suggests that substrate particle size and P reduction and regulation might have a strong influence on the maximization of sporulation and colonization of R. irregularis in sand substrate-based culture.

Quantitative Assessment of Abiotic Stress on the Main Functional Phytochemicals and Antioxidant Capacity of Wheatgrass at Different Seedling Age

The wheat seedlings of 6 days old were daily subjected to ultraviolet irradiation (irradiating for 5, 10, 20, 40, and 60 min/day, respectively), Polyethylene glycol 6000 (5, 10, 15, 20, 25% in 1/2 Hoagland solution, respectively), and salinity solution (10, 25, 50, 100, 200 mM in 1/2 Hoagland solution, respectively), while the control group (CK) was supplied only with the Hoagland solution. The wheatgrass was harvested regularly seven times and the total soluble polysaccharides, ascorbic acid, chlorophyll, total polyphenol, total triterpene, total flavonoid, and proanthocyanins content were tested. The antioxidant capacity was evaluated through 2,2′-azino-bis (3-ethylbenzthia-zoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging ability, and ferric ion reducing power. Technique for order preference by similarity to ideal solution (TOPSIS) mathematical model was adopted to comprehensively assess the functional phytochemicals of the different treatments. The results showed that the accumulation patterns of phytochemicals under abiotic stress were complex and not always upregulated or downregulated. The antioxidant activity and functional phytochemicals content of wheatgrass were significantly affected by both the stress treatments and seedling age, while the latter affected the chemicals more efficiently. The top five highest functional phytochemicals were observed in the 200 mM NaCl treated group on the 21st and 27th day, 25% PEG treated group on the 24th day, 200 mM NaCl treated group on the 24th day, and the group of 40 min/day ultraviolet exposure on 27th day.

In vivo polyploidy induction of Phalaenopsis amabilis in a bubble bioreactor system using colchicine

Phalaenopsis amabilis Blume var. grandiflora Bateman is economically important as cut and pot flower. Polyploidy is considered as a valuable tool in improvement and evolution of ornamental plants. Protocorm-like bodies (PLBs) of P. amabilis were cultured on Murashige and Skoog medium containing 0.20 mg L-1 IBA together with 2.00 mg L-1 KIN and 1.00 g L-1 activated charcoal and grown for a period of five months. Fully-developed plantlets from in vitro grown PLBs were immersed in a bubble reactor filled with half-strength Hoagland solution containing the antimitotic agent colchicine (0.05%, 0.10% and 0.15%, w/v) for 72 h with a few drops (1 mL of 0.1%) of octylphenoxypolyethoxyethanol or Nonidet (P-40) as a surfactant. Plantlets were aerated to prevent hypoxia. Colchicine-treated and untreated plantlets were transferred to pots for a period of 60 days. Tetraploidy was successfully induced by 0.15% colchicine. Polyploidy levels were firstly detected using flow cytometry and then confirmed by cytological and morphological observations. The chromosome number was 2n = 2x = 38 in diploids and 2n = 4x = 76 in tetraploid. Incubation of plantlets in liquid medium containing 0.15% colchicine induced the maximum recovered tetraploids with minimum frequency of survival (50%). The tetraploid plants were more compact and exhibited round and thick leaves with darker green color than diploids. Stomata size in tetraploids were larger with less density than diploids. Chloroplast number in guard cells of tetraploids was about two times more than that of control. These results indicate that induction of tetraploids are a reliable and powerful tool for generation of novel phenotypes with ornamental and horticultural value for genetic improvement and breeding. Produced tetraploids in current study have potential in the ornamental/floriculture trade.

Tolerance of Daffodil (Narcissus poeticus L. c.v. “Ice Folies”) to Nickel Contaminated Media

The objective of this study was to determine the tolerance of daffodil (Narcissus poeticus L. c.v. “Ice Folies”) as a hyperaccumulator plant to nickel contaminated media. This research was carried out in a completely randomized plot experimental design with three replications in green house conditions. Four doses of nickel (control, 25 mg kg-1, 50 mg kg-1, 75 mg kg-1) were applied to each growing media having 500 g soil:sand mixture in 2:1 ratio. The distillate water was used in irrigation and Hoagland solution was applied for fertilization. At the end of the experiment, effects of nickel applications on leaf length, plant length, flower length (P<0.01) and flower diameter, stem diameter (P<0.05) were found significant, except leaf number and leaf length. The lowest first flowering time, full flowering time and first floret withering time were obtained in control and 75 mg kg-1 nickel application. The highest leaf length (341.60 mm), plant length (418.24 mm), flower length (70.74 mm) and stem diameter (7.63 mm) were obtained in 75 mg kg-1 nickel application. The highest flower diameter was found as 78.35 mm in 25 mg kg-1 nickel application. Generally, while the nickel doses increased flowering time, leaf length, plant length, flower length and flower diameter increased.

EVALUATION OF BIOACTIVE COMPONENTS AND ANTIOXIDANT ACTIVITY OF VERNONIA ELAEAGNIFOLIA DC. (ASTERACEAE) IN GLYCOPHYTIC AND HALOPHYTIC CONDITIONS

Objective: The investigate some of the antioxidant activities and bioactive potentials of Vernonia elaeagnifolia grown hydroponically in glycophytic and halophytic conditions. Methods: Plants were grown in Hoagland solution and subjected to (Sodium chloride (NaCl) treatments. Plants cultivated without salt stress served as the control. The phytochemical analysis was done with the help of Gas Chromatography-Mass Spectrometry (GC-MS) and antioxidants were analyzed following standard procedures using UV-Visible Spectrophotometer. Results: Significant changes were observed in the presence of antioxidants like superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), total polyphenols, proline and ascorbic acid. GPX and proline proved to be the major components in imparting salinity stress tolerance. The control showed the presence of 23 bioactive components while the treatment contained 19 components. Conclusion: The study thus provides information regarding the place of collection of the particular plant. Glycophytic conditions prove to be the best choice in terms of bioactive components and fatty acid contents. The investigations reveal that the plant contains several bioactive components and antioxidants, which prove it as a promising plant for developing potential drugs.