M. Masroor A. Khan

Stimulation of crop productivity, photosynthesis and artemisinin production in Artemisia annua L. by triacontanol and gibberellic acid application

Abstract Artemisia annua L. is an aromatic-antibacterial herb that destroys malarial parasites, lowers fevers and checks bleeding, and of which the secondary compound of interest is artemisinin. Enhanced production of the artemisinin content in the whole plant is highly desirable. Keeping in mind, the importance of this valuable antimalarial plant, field experiments were conducted to investigate the effects of triacontanol alone and in combination with gibberellic acid on growth attributes, photosynthesis, enzymatic activities, essential oil and artemisinin content and yield of Artemisia. The results indicate that combination of triacontanol and gibberellic acid (1.5 mg l−1+75 mg l−1) significantly increased activities of nitrate reductase and carbonic anhydrase by 25.9% and 21.5%, and net photosynthetic rate, stomatal conductance and internal CO2 by 25.4%, 14.1% and 15.4% higher, respectively, when compared to unsprayed plants. This combined treatment also significantly enhanced artemisinin content and yield (29% and 61% higher values).

Salicylic acid-induced physiological and biochemical changes in lemongrass varieties under water stress

Abstract Salicylic acid (SA) treatment reduces the damaging action by water deficit on growth and accelerates a restoration of growth processes. The aim of the present work was to study the physiological and biochemical alteration induced by SA in lemongrass plants under stress conditions. Therefore, a pot culture experiment was conducted to test whether SA application at concentration of (10−5 M) through foliar spray could protect lemongrass (Cymbopogon flexuosus Steud. Wats.) varieties (Neema and Krishna), subjected to drought stress on the basis of growth parameters and biochemical constituents, proline metabolism and quality attributes including citral content. The treatments were as follows: (i) 100% FC + 0 SA; (ii) 75% FC + 0 SA; (iii) 50% FC + 0 SA; (iv) 75% FC + 10−5 M SA; and (v) 50% FC + 10−5 M SA. The growth parameters were significantly reduced under the applied water stress levels; however, foliar application of salicylic acid (10−5 M) improved the growth parameters in stress-affected plants. The plants under water stress exhibited a significant increase in activities of nitrate reductase and carbonic anhydrase, and electrolyte leakage, proline content, free amino acid and in PEP carboxylase activity. Content and yield of essential oil also significantly decreased in plants that faced water stress. Thus, it was concluded that variety Neema is the more tolerant variety as compared to Krishna on the basis of content and oil yield and well adapted to drought stress conditions.

Methyl jasmonate counteracts boron toxicity by preventing oxidative stress and regulating antioxidant enzyme activities and artemisinin biosynthesis in Artemisia annua L.

Boron is an essential plant micronutrient, but it is phytotoxic if present in excessive amounts in soil for certain plants such as Artemisia annua L. that contains artemisinin (an important antimalarial drug) in its areal parts. Artemisinin is a sesquiterpene lactone with an endoperoxide bridge. It is quite expensive compound because the only commercial source available is A. annua and the compound present in the plant is in very low concentration. Since A. annua is a major source of the antimalarial drug and B stress is a deadly threat to its cultivation, the present research was conducted to determine whether the exogenous application of methyl jasmonate (MeJA) could combat the ill effects of excessive B present in the soil. According to the results obtained, the B toxicity induced oxidative stress and reduced the stem height as well as fresh and dry masses of the plant remarkably. The excessive amounts of soil B also lowered the net photosynthetic rate, stomatal conductance, internal CO2 concentration and total chlorophyll content in the leaves. In contrast, the foliar application of MeJA enhanced the growth and photosynthetic efficiency both in the stressed and non-stressed plants. The excessive B levels also increased the activities of antioxidant enzymes, such as catalase, peroxidase and superoxide dismutase. Endogenous H2O2 and O2− levels were also high in the stressed plants. However, the MeJA application to the stressed plants reduced the amount of lipid peroxidation and stimulated the synthesis of antioxidant enzymes, enhancing the content and yield of artemisinin as well. Thus, it was concluded that MeJA might be utilized in mitigating the B toxicity and improving the content and yield of artemisinin in A. annua plant.

Exogenous nitric oxide donor protects Artemisia annua from oxidative stress generated by boron and aluminium toxicity

Nitric oxide (NO) is an important signal molecule modulating the response of plants to environmental stress. Here we report the effects of boron (B) and aluminium (Al) contamination in soil, carried out with or without application of exogenous SNP (NO donor), on various plant processes in Artemisia annua, including changes in artemisinin content. The addition of B or Al to soil medium significantly reduced the yield and growth of plants and lowered the values of net photosynthetic rate, stomatal conductance, internal CO(2) concentration and total chlorophyll content. The follow-up treatment of NO donor favoured growth and improved the photosynthetic efficiency in stressed as well as non-stressed plants. Artemisinin content was enhanced by 24.6% and 43.8% at 1mmole of soil-applied B or Al. When SNP was applied at 2mmole concentration together with either 1mmole of B and/or Al, it further stimulated artemisinin biosynthesis compared to the control. Application of B+Al+SNP proved to be the best treatment combination for the artemisinin content in Artemisia annua leaves.

Triacontanol: a potent plant growth regulator in agriculture

Abstract Triacontanol (TRIA) is a natural plant growth regulator found in epicuticular waxes. It is used to enhance the crop production in millions of hectares, particularly in Asia. Quite a number of researchers have reported the TRIA-mediated improvement in growth, yield, photosynthesis, protein synthesis, uptake of water and nutrients, nitrogen-fixation, enzymes activities and contents of free amino acids, reducing sugars, soluble protein, and active constituents of essential oil in various crops. Expectedly, TRIA enhances the physiological efficiency of the cells and, thus, exploits the genetic potential of plant to a large extent. In fact, TRIA increased free amino acids, reducing sugars, and soluble protein of rice (Oryza sativa L.) and maize (Zea mays L.) within 5 min. TRIA elicited the appearance of L(+)-adenosine within 1 min in the roots of plants, the shoots of which were sprayed with nanomolar concentrations of TRIA. TRIA and octacosanol (OCTA), the primary alcohols, are ubiquitous in the environment. OCTA was reported to inhibit the activity of TRIA in the seedlings of rice (Oryza sativa L.) at equimolar concentrations; and both TRIA and OCTA elicited a second messenger, known as OCTAM and triacontanol second messenger (TRIM), respectively. TRIA rapidly increases the ratio of L(+)- to D(–)-adenosine, probably at the tonoplast. However, it is to be resolved as to how TRIA elicits L(+)-adenosine and what is the source of L(+)-adenosine in plants. Based on known metabolic processes, de novo synthesis of L(+)-adenosine is unlikely, because of the rapidity of the response. TRIA-mediated increase in dry matter production could influence the inter-relationship between primary and secondary metabolism, leading to increased biosynthesis of secondary products. Various studies present strong evidences that application of TRIA applied either to the root medium or to leaves enhanced the growth and yield of vegetables and other crops, including agronomic and horticultural crops as well as medicinal and aromatic crop plants under normal and adverse conditions. However, further investigations are required to elucidate the possible role of TRIA on plant growth regulation, physiological activities and secondary metabolite biosynthesis regarding medicinal and aromatic plants subjected to abiotic stress. The present review covers the pivotal role of TRIA in plant growth and development, its mode of action and its significance in improving the crop productivity and quality of agricultural crops.

Cumulative Effect of Soil and Foliar Application of Nitrogen, Phosphorus, and Sulfur on Growth, Physico-Biochemical Parameters, Yield Attributes, and Fatty Acid Composition in Oil of Erucic Acid-Free Rapeseed-Mustard Genotypes

ABSTRACT The feasibility of split (soil + foliar) applications of nitrogen (N) and phosphorus (P) and addition of a small quantity of sulfur (S) in the spray was tested for improving performance of rapeseed-mustard genotypes in a factorial randomized field experiment. Three genotypes (two erucic acid free, viz. Brassica napus L. cv. ‘Hyola PAC – 401’ and Brassica juncea L. Czern. and Coss. cv. ‘TERI (0E) M 21-Swarna’, and one best performing high yielding Brassica juncea L. cv. ‘Rohini’ as a check) were grown with four soil (B) plus foliar (F) applications of N, P, and S with uniform basal 30 kg potassium (K) ha− 1 (K30), viz. (i) the optimum soil-applied treatment supplemented with the spray of deionized water (BN90P30 + Fw) comprising control, (ii) BN70P30 + F N20, (iii) BN70P28 + FN20P2, and (iv) BN70P28 + FN20P2S2. Soil Plus foliar application of nutrients, particularly BN70P28 + FN20P2S2, improved their performance with respect to growth characteristics (shoot length plant− 1, leaf number plant− 1, area leaf− 1, leaf area index, fresh weight plant− 1, and dry weight plant− 1), physico-biochemical parameters (net photosynthetic rate, stomatal conductance, carboxylation efficiency, water use efficiency, carbonic anhydrase activity, leaf NPK content, and N use efficiency), yield attributes (pod number plant− 1, seed number pod− 1, 1000-seed weight, seed yield ha− 1, oil content, and oil yield ha− 1), and fatty acid composition in oil of these genotypes. The cultivar ‘Hyola PAC-401’ performed best particularly with BN70P28 + FN20P2S2. The improvement in the response of genotypes to the split application of nutrients may be attributed to their ready availability through foliar application.

Phosphorus ameliorates crop productivity, photosynthesis, nitrate reductase activity and nutrient accumulation in coffee senna (Senna occidentalis L.) under phosphorus-deficient soil

Abstract Coffee senna (Senna occidentalis L.) plants were subjected to five phosphorus levels: 0, 25, 50, 75 and 100 mg P per kg soil (P0, P1, P2, P3 and P4, respectively). A pot culture experiment was conducted in a net house, AMU, Aligarh, India, under phosphorus-deficient soil. The present data indicates that soil-applied phosphorus significantly ameliorates most of the attributes studied. Out of five phosphorus levels, 75 mg P per kg soil (P3) proved best and enhanced fresh and dry weights, total chlorophyll and carotenoid content, nitrate reductase activity and leaf-NPK and Ca content, analyzed at 120, 270 and 300 days after sowing (DAS). The number of pods, seed-yield per plant and seed-protein content (330 DAS) were significantly enhanced by the P3 level, except the number of seeds per pod, 100-seed weight and total anthraquinone glycosides content, respectively. Transpiration rate, stomatal conductance and net photosynthetic rate were also enhanced by this treatment.

Salicylic acid restrains nickel toxicity, improves antioxidant defence system and enhances the production of anticancer alkaloids in Catharanthus roseus (L.)

Salicylic acid (SA) has been reported to ameliorate various stresses in plants. In order to explore the role of SA under nickel (Ni) stress, thirty-days old plants of periwinkle (Catharanthus roseus L.) were supplied with eight treatments comprising basal application of Ni (0, 50, 100 and 150 mg kg(-1)) and foliar application of SA (0 and 10(-5)M) under net house conditions. Ni application significantly reduced the growth attributes including plant height, leaf-area index and fresh and dry weights of shoot and root. Increasing Ni concentration led to a gradual decrease in photosynthetic parameters and activities of nitrate reductase and carbonic anhydrase. The plants, undergoing Ni stress, exhibited a significant increase in the activity of superoxide dismutase, catalase and peroxidase together with an increase in electrolyte leakage and proline content. Total alkaloid content was also declined in Ni-treated plants. Foliar application of SA (10(-5)M) reduced the deleterious effects of Ni on plant growth, accelerating the restoration of growth processes. SA also improved the total alkaloid content under normal as well as adverse conditions. Foliar spray of SA significantly improved the content of anticancer alkaloids vincristine (by 22.2%) and vinblastine (by 50.0%) in plants treated with 150 mg kg(-1) of Ni.

Depolymerized carrageenan ameliorates growth, physiological attributes, essential oil yield and active constituents of Foeniculum vulgare Mill.

Irradiated carrageenan (IC) elicits an array of plant defense responses and biological activities in plants. An experiment was carried out in the naturally illuminated conditions of net house in order to assess the effects of foliar spray of IC on agricultural performance of fennel (Foeniculum vulgare Mill.), which is a high-value essential oil bearing medicinal crop used in pharmaceutical, food and cosmetic industries. There were applied four IC concentrations (40, 60, 80 and 100 mg L(-1)) as foliar sprays. Application of IC significantly improved the growth attributes, physiological and biochemical parameters, essential oil yield and the contents of main components of essential oil of fennel. IC applied at 80 mg L(-1) enhanced these parameters maximally. Unirradiated carrageenan and deionized water had no effect on the attributes studied. Moreover, GLC analysis revealed a significant increase in the components of essential oil, viz. fenchone (4.48-7.82%) and anethole (78.38-86.08%) compared to the control.

Irradiated sodium alginate improves plant growth, physiological activities and active constituents in Mentha arvensis L.

Sodium alginate, irradiated by Co-60 gamma rays in solid state, elicits plant growth promoting responses in various plants. Irradiated sodium alginate (ISA) was applied as a foliar spray on mint (Mentha arvensis L.) to investigate its effect on plant growth, physiological attributes and herbage yield as well as on content and yield of essential oil and its components (menthol, L-menthone, isomenthone and methyl acetate). A simple pot experiment was conducted applying five concentrations of ISA, viz. 25, 50, 75, 100 and 125 mg L, as foliar sprays. GPC study revealed formation of lower molecular weight oligomer fractions in irradiated samples which could be responsible for plant growth promotion in the present work. Of the five ISA concentrations, 100 mg L proved the best. As compared to the control, the ISA applied at 100 mg L resulted in the highest values of all physiological parameters at 100 and 120 days after planting.