Brassinosteroid-mediated enrichment in yield attributes, active constituents and essential oil production in Mentha arvensis L.

Recently, brassinosteroids (BRs) have emerged as a new group of growth promoting phytohormones. 28-homobrassinolide (HBR) is one of the several brassinosteroids, the role of which in enhancing growth, productivity and quality of plants, via improving various physiological processes, has been established both under stress and normal conditions. Out of a large number of essential oil bearing plants, mint (Mentha arvensis L.) constitutes the most important source of therapeutic agents used in the alternative systems of medicine. The mint plant has marvelous medicinal and aromatic values. In view of enhancing yield and quality of this medicinally important plant, a pot experiment was conducted under natural conditions of net house. The study was aimed at exploring the effect of four concentrations of HBR (10^?0, 10^?8, 10^?7 and 10^?6 M) on the performance of mint with regard to physiological attributes, herbage yield, content and yield of essential oil, and active constituents at 100 and 120 days after planting. The foliar application of HBR enhanced physiological attributes, herbage yield and the yield and content of most of the active constituents (menthol, L-methone, isomenthone and menthyl acetate) of mint at both the stages, with 10^?7 M concentration proving the best. However, the next higher concentration of HBR (10^?6 M) exhibited no further increase in the values of the attributes studied. Rather, 10^?6 M was slightly inferior to 10^?7 M concentration; but it always proved significantly better than the control.     

Augmentation of photosynthesis,crop productivity,enzyme activities and alkaloids production in Sadabahar (<Emphasis Type="Italic">Catharanthus roseus</Emphasis> L.) through application of diverse plant growth regulators

Exogenous application of plant growth regulators (PGRs) has vital impact on the growth and productivity of plants. Foliar application of selected PGRs, viz. indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), naphthalene acetic acid (NAA), 6-benzylaminopurine (BAP), kinetin (KIN), thidiazuron (TDZ), gibberellic acid (GA3), salicylic acid (SA), homobrassinosteroids (HBR), and triacontanol (TRIA), were carried out in order to assess the effects on growth of two cultivars (Rosea and Alba) of Catharanthus roseus L. G. Don. The Rosea and Alba plants were sprayed with PGRs (10⁻⁷ M) at 60 days after planting (DAP). Shoot and root lengths, plant fresh and dry weights, leaf-area index, total chlorophyll and carotenoids content, net photosynthetic rate, nitrate reductase and carbonic anhydrase activities, and leaf essential nutrients (N, P, and K) were analyzed at 150 DAP while yield attributes and total alkaloids of leaves and roots, contents of vincristine and vinblastine alkaloids were measured at 210 DAP. The results showed that HBR significantly improved most of the growth attributes. Application of HBR, KIN, and GA3 resulted in the ameliorative effects on plant productivity, physiological and biochemical parameters as compared to the unsprayed (control) plants. The effect of TDZ was not significantly different than the control plants. GA3 application significantly increased the vincristine content (7.3%) while TDZ exhibited reduced vincristine content. The effect of other PGR was insignificant towards vincristine and vinblastine contents. The response of Rosea toward exogenous PGRs application was better than Alba in terms of crop productivity, physiological and biochemical parameters, and alkaloid production.     

Potassium Uptake in Relation to Drought Tolerance of Chickpea Under Rain-Fed Conditions

Potassium is accumulated in substantial amount in water stressed plants, contributing to osmotic adjustment. Eight varieties of chickpea were field grown according to randomized block design with three replications during two consecutive crop seasons to explore the role of K uptake in drought tolerance of chickpea under rain-fed conditions. Plant water relation and other physiological parameters were measured at 70 days after planting, while potassium uptake and yield parameters were recorded at harvest. The varieties were divided into high (HKU), medium (MKU) and low (LKU) K uptake groups, using average K uptake across the seasons. All the data were statistically analyzed group-wise. The HKU, followed by MKU and LKU (i.e. HKU>MKU>LKU) gave the highest values for most of the parameters studied including seed yield and crop biomass. The HKU also exhibited the lowest osmotic potential together with maintenance of elevated water content and turgor in plants compared to MKU and LKU. There was significant season-group interaction regarding most parameters including seed yield and crop biomass. However, such an interaction was not significant regarding K uptake, though varietal group pattern of K uptake was similar to that of seed yield and crop biomass (i.e. HKU>MKU>LKU), indicating that promising chickpea varieties might be selected under rain-fed conditions using K uptake.     

Vegetation-environment relationships in the forests of Chitral district Hindukush range of Pakistan

We investigated the composition of plant communities to quantify their relationships with environmental parameters in the Chitral Hindukush range of Pakistan. We sampled tree vegetation using the Point Centered Quarter (PCQ) method while understory vegetation was sampled in 1.5-m circular quadrats. Cedrus deodara is the national symbol of Pakistan and was dominant in the sampled communities. Because environmental variables determine vegetation types, we analyzed and evaluated edaphic and topographic factors. DCA-Ordination showed the major gradient as an amalgam of elevation (p<0.05) and slope (p<0.01) as the topographic factors correlated with species distribution. Soil variables were the factors of environmental significance along DCA axes. However, among these factors, Mg2+ , K + and N2+ contributed not more than 0.054% 0.20% and 0.073%, respectively, to variation along the first ordination axis. We conclude that the principal reason for weak or no correlation with many edaphic variables was the anthropogenic disturbance of vegetation. The understory vegetation was composed of perennial herbs in most communities and was most dense under the tree canopy. The understory vegetation strongly regulates tree seedling growth and regeneration patterns. We recommend further study of the understory vegetation using permanent plots to aid development of forest regeneration strategies.     

EFFECT OF ZINC NUTRITION ON GROWTH,YIELD, AND QUALITY OF FORAGE SORGHUM IN RESPECT WITH INCREASING POTASSIUM APPLICATION RATES

A two-year field study was conducted to determine the effect of two zinc (Zn) levels [0 and 10 kg zinc sulfate (ZnSO₄) ha^?1] in respect with four potassium (K) levels (0, 20, 40 and 60 kg K₂O ha^?1) on growth, yield and quality of forage sorghum. The soil of the experimental field was loamy sand (Inceptisol), carrying 70, 08, 77, and 0.51 mg nitrogen (N), phosphorus (P), K, and Zn kg^?1 soil, respectively. Increasing K levels significantly improved most of the growth, yield, and quality attributes gradually irrespective of the Zn levels. Zinc applied at 10 kg ZnSO₄ ha^?1 proved significantly better than no zinc application at various K application rates. The benefit of zinc application increased progressively with increasing K rates for most of the parameters studied, indicating significant response of the crop to positive K × Zn interaction in plants in respect with K and Zn application to the soil. Accordingly, 60 kg K₂O ha^?1 applied with10 kg ZnSO₄ ha^?1 boosted most of the attributes maximally. It resulted in about 20–40% increase in growth attributes, 25% increase in fresh matter yield, 36–38% increase in dry matter yield, and 38% increase in protein yield compared to the comparable K level applied without zinc. It also enhanced N uptake by 38%, P uptake by 5–19%, K uptake by 40–42%, and Zn uptake by 114–144%. Across the K rates, application of 10 kg ZnSO₄ surpassed no zinc application by 30–35% in N uptake, by 8–15% in P uptake, by 33–36% in K uptake, by 120–140% in Zn uptake, by 19–21% in fresh matter yield, by 29–31% in dry matter yield, and by 30–34% in protein yield.     

Utilizing the γ-Irradiated Sodium Alginate as a Plant Growth Promoter for Enhancing the Growth, Physiological Activities, and Alkaloids Production in Catharanthus roseus L.

Sodium alginate is a polysaccharide that is largely obtained from the brown algae (Sargassum sp.).It has been used as a wonderful growth promoting substance in its depolymerized form for various plants.The aim of this study was to find out the effects of various concentrations of γ-irradiated sodium alginate (ISA),viz.,deionized water (control,T0),20 (T1),40 (T2),60 (T3),80 (T4),and 100 ppm (T5) on the agricultural performance of Catharanthus roseus L.(Rosea) in terms of growth attributes,photosynthesis,physiological activities,and alkaloid production.The present work revealed that ISA applied as leaf-sprays at concentrations from 20 to 100 ppm might improve growth,photosynthesis,physiological activities,and alkaloid production in C.roseus L.significantly.Of the various ISA concentrations,80 ppm proved to be the best one compared to other concentrations applied.     

Growth,photosynthetic efficiency and metabolic alterations associated with exogenous hydrogen peroxide in <Emphasis Type="Italic">Artemisia annua</Emphasis>: Overproduction of artemisinin

Artemisinin, a sesquiterpene lactone with a peroxide linkage, has been held responsible for antimalarial activity of the Artemisia annua L. Recently, it was reported that reactive oxygen species (ROS) play important role in the biosynthesis of artemisinin by catalyzing some important intermediate steps. The effect of exogenously supplied hydrogen peroxide (1.00 mM and 2.00 mM H₂O₂), in two ways, foliar and as soil drench, was worked out in terms of growth, alteration in photosynthesis, oxidative damage, antioxidant defense enzymes and artemisinin level in exposed plants. Application of H₂O₂ positively affect the growth of the treated plants; and increment in net photo synthetic rate, stomatal conductance, internal CO₂ and chlorophyll content in the H₂O₂ exposed A. annua plants was noted. A significant upregulation in antioxidant enzymes viz. catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) was observed as a result of exogenous H₂O₂ treatment when applied foliarly or as soil drench. H₂O₂application either by 1.00 mM or 2.00 mM stimulated artemisinin levels, however, 2.00 mM H₂O₂ applied as soil drench elicited artemisinin production more rapidly compared to other treatments. Therefore, results suggest that exogenous H₂O₂ may stimulate growth by inducing antioxidant defense system and increase the artemisinin levels in Artemisia annua plants.     

Modulation of defence responses by improving photosynthetic activity,antioxidative metabolism,and vincristine and vinblastine accumulation in <Emphasis Type="Italic">Catharanthus roseus</Emphasis> (L.) G. Don through salicylic acid under water stress

A pot experiment was conducted to find out whether the foliar spray of salicylic acid (SA) could successfully ameliorate the adverse effects of water stress on periwinkle. Pots were irrigated with ground water regularly as a control and other treatments were given as 15 and 30 days interval drought (DID) at 30 DAS. Plants were uprooted randomly at 46 and 61 DAS, washed carefully and separated into root, stem and leaf for analyses. A uniform concentration (10⁻⁵ mol/l) of salicylic acid (SA) was applied as a foliar spray at the vegetative stage. Water stress significantly reduced the growth attributes including plant height, leaf-area index, shoot and root fresh weights, shoot and root dry weights. Long term water stress led to a gradual decrease in photosynthetic parameters and activities of nitrate reductase and carbonic anhydrase. Ascorbic acid, total alkaloids and antioxidant enzymes: superoxide dismutase, catalase and peroxidase increased in stress faced plants. Foliar application of SA (10⁻⁵ M) reduced the damaging effect of stress on plant growth and accelerated the restoration of growth processes. It not only improved the growth parameters but also partially reversed the effects of salinity. Total alkaloid content was improved by SA application both in unstressed and stressed plants. Foliar spray of SA not only overcame the adverse effect of stress but also improved the content of vincristine and vinblastine in stressed plants.     

Optimizing nitrogen levels combined with gibberellic acid for enhanced yield, photosynthetic attributes, enzyme activities, and artemisinin content of Artemisia annua

Artemisia annua L. is an aromatic-antibacterial herb that destroys malarial parasites, lowers fever, and checks bleeding, and from which the secondary compound of interest is artemisinin. It has become increasingly popular as an effective and safe alternative therapy against malaria, and its derivatives are effective against multidrug resistant Plasmodium falciparum strains. Nitrogen is required by the plants in the largest quantity and is most limiting where biomass production is desired. On the other hand, gibberellic acid plays an important role in flowering, growth, and development and also in other physiological and biochemical processes. The feasibility of foliar GA₃ (75 mg·L⁻¹) alone or with varying levels of soil applied nitrogen (40, 80, and 120 mg·kg⁻¹ soil) was tested on A. annua in the present study. The application of GA₃ proved effective in alleviating the growth, photosynthesis, and enzyme activities of A. annua. However, N levels combined with GA₃ showed better responses, and further improvement in these parameters was observed. Furthermore, the most important task we were interested in was to increase the artemisinin content and its yield on a per plant basis. The N combination (80 mg·kg⁻¹ soil) together with GA₃ augmented the content (21.8% more) and yield (55.8% more); this is true for both the treated plants, which were more than the control.     

Salicylic acid acts as potent enhancer of growth,photosynthesis and artemisinin production in <Emphasis Type="Italic">Artemisia annua</Emphasis> L.

Plant secondary metabolites constitute the most important class of natural products with diverse and valuable chemical properties and biological activities. Artemisinin, isolated from Artemisia annua L., is potentially a drug that could be effective against multidrug-resistant strains of the malarial parasite, Plasmodium. Salicylic acid (SA) acts as a potential plant growth regulator and plays an important role in regulating a number of plant physiological and biochemical processes. The present study was conducted to assess the alterations in plant growth, photosynthetic capacity, enzyme activities, and content and yield of artemisinin in Artemisia annua L. in response to foliar application of SA. Four levels of SA (0.00, 0.25, 0.50, and 1.00 mM SA) were applied on the aboveground plant parts. Plant height and dry weight were altered significantly as the level of SA increased. Besides, application of SA positively improved chlorophyll and carotenoid contents. Furthermore, significant enhancement in net photosynthetic rate (31.7%) and the activity of nitrate reductase (17.2%) and carbonic anhydrase (10.9%) was noticed as the level of SA was increased from 0.00 to 1.00 mM SA. Most importantly, the content and yield of artemisinin was positively regulated by the SA. In comparison to no SA application (control), SA at 1.00 mM increased the content and yield of artemisinin by 25.8 and 50.0%, respectively.