Cheruth Abdul Jaleel’s research while affiliated with Annamalai University and other places

Petunia (Petunia hybrida Hort. Vilm-Andr) is popularly grown in the landscapes of UAE. In order to standardize a seed programming technique to induce drought tolerance, a three stage programming of seeds involving imbibitions, osmopriming and acclimation have been developed. Triadimefon, a derivative of triazole, at 25 and 50 ppm was combined with potassium chloride as osmopriming agent and acclimation done at 28-32°C. The plants raised from programmed seeds were subjected to two frequencies of irrigation; daily and once in three days. Photosynthetic pigments, free phenols, amino acids, proline and total sugars were the parameters used to monitor the efficiency of protection against induced moisture stress by the wider frequency of irrigation. However, the degree of protection by triadimefon was enhanced if the seeds were subjected to imbibitions, osmopriming and acclimation. In addition to protection against moisture stress, the programming techniques influenced the uptake of major elements like nitrogen, phosphorus and potassium, but the general trend with nitrogen was that the uptake pattern is same except that triadimefon and KCl slightly enhanced the uptake of nitrogen increasing the tissue concentration. When the interaction effect is considered 50 ppm of triadimefon with KCl and irrigation once in three days showed significantly high amount of phosphorus (0.8512%).

Irradiation can adversely affect plant growth and development. The radio protective activity mechanism by glycinebetaine in plants is not known. Gamma rays at doses 0.0, 25, 50, 100, and 150 Gray (Gy) from a cobalt source (60Co) with strength of 500 Ci and the dose rate of 0.54 Gy·min−1 were applied presowing to dry seeds of fenugreek (Trigonella foenum-graecum L.). Total dry weight and levels of chlorophyll, total protein, photosynthetic efficiency (14CO2-fixation), accumulation of reducing, nonreducing, and total soluble sugars were reduced compared with unirradiated control. The general response to increased glycinebetaine dose and increasing irradiation dose was a reduction in measured variables as irradiation dose increased and with higher values for plants treated with 50 mM glycinebetaine. The exceptions were for total chlorophyll where values from plants treated with 150 Gy were equal regardless of glycinebetaine dose and for H2O2 amount, which increased as irradiation dose increased. For this last effect values were higher when the no glycinebetaine dose was applied to plants. Glycinebetaine protection was more pronounced against irradiation stress at lower doses of γ-rays. Posttreatment of irradiated seeds with glycinebetaine partially alleviated adverse effects of radiation. Pretreatment of seeds with glycinebetaine may play an effective role in the radio-repair mechanism.

In this study, 5 μM ABA and GA3 concentration were used to study the effect of these growth regulators on the andrographolide content and antioxidant potentials of Andrographis paniculata. The growth regulators were applied by means of foliar spray during morning hours. A significant enhancement in non-enzymatic antioxidant contents was observed in all sampling days in A.paniculata plants under ABA and GA3 treatments. Ascorbic acid and α-tocopherol content was increased significantly under the growth regulator treatments in leaves, stem and roots of A. paniculata. The activities of antioxidant enzymes such as ascorbate peroxidase, superoxide dismutase and catalase were increased by ABA and GA3 treatments in the leaves, stem and roots of A. paniculata plants. The HPLC analysis was used to quantify the andrographolide content in control and growth regulator treated plants. The growth regulators ABA and GA3 treated plants showed increased contents of andrographolide when compared to control.

Salt stress-induced changes in antioxidant enzymes, lipid peroxidation, proline and glycine betaine contents, and proline-metabolizing enzymes were examined in the leaves of two mulberry cultivars (Local and Sujanpuri). With increasing salinity up to 150 mM NaCl, superoxide dismutase, catalase, ascor-bate peroxidase, guaiacol peroxidase, glutathione reductase, and monodehydroascorbate reductase activities were increased in both cultivars as compared to control, but more pronounced increase was observed in cv. Local. Salt stress enhanced the rate of lipid peroxidation (as indicated by increasing MDA content) in both cultivars. Under NaCl stress, cv. Local showed less change in the MDA content than cv. Sujanpuri. Salt stress resulted in a significant accumulation of free proline in mulberry leaves, and more accumulation was detected in cv. Local than cv. Sujanpuri. The leaves of cv. Local showed 9-fold accumulation of glycine betaine in comparision with cv. Sujanpuri after 20 days at 150 mM NaCl. A decrease in proline oxidase activity and an increase in γ-glutamyl kinase activity were observed with increasing NaClconcentration. The relative water content and electrolyte leakage also decreased after increasing the NaCl concentration, but a decrease was more pronounced in cv. Sujanpuri than in cv. Local. The results indicate that oxidative stress may play an important role in salt-stressed mulberry plants and cv. Local have more efficient antioxidant characteristics, which could provide for a better protection against oxidative stress. Key words Morus alba -antioxidants-glycine betaine-lipid peroxidation-proline-salinity

Incorporation of compost in soil will not only protect the environment, but also take advantage of the nutrients and organic matter contained in the compost to enhance soil fertility and crop production. Field experiments were carried out during the 2006/2007 and 2007/2008 growing seasons at the College of Food and Agriculture Farm, United Arab Emirates University. The experiments were established in randomized complete block design (RCBD) with four replications. The plot dimension was 3.2m×2.8 m, with four rows per plot. The treatments were designed to study the effect of compost rates on the potato production and soil fertility properties. Five rates of compost were investigated (control, 40, 80, 120 ton compost per hectare; and inorganic fertilizers (250 kg N·ha−1, 250 kg P2O5·ha−1 and 300 kg K2O·ha−1)). Results of the first growing season 2006/2007 showed that marketable tuber yield, plant height and specific gravity were greater in compost amended soil than in non-amended soil even if inorganic fertilizers were added. Application of 120 ton compost per hectare gave the highest total tubers number, marketable tuber yield, height and specific gravity. Keywordscompost-soil fertility-tuber quality-minerals-crop production- Solanum tuberosum

The effect of plant growth promoting rhizobacteria such as Azotobacter, Bacillus and Pseudomonas was tested separately or in combination in Catharanthus roseus for two consecutive years (2005 and 2006). The combinations of above mentioned PGPR strains significantly increased plant height, root length, root girth and alkaloid content in C. roseus in comparison to the control. In addition, all nutrient contents (N, P, K, Ca and Mg) were also significantly increased as compared to the control. The maximum N, P, K content was obtained from the combination of PGPR treatment. The results of this study suggest that PGPR applied in combination have the potential to increase the plant growth, alkaloid content and nutrient content of C. roseus.

The present investigation was carried out with the objectives to understand the effect of paclobutrazol, gibberellic acid and Pseudomonas fluorescens on the enzymatic antioxidants like Ascorbate peroxidase (APX, EC: 1.11.1.11), Superoxide dismutase (SOD, EC: 1.15.1.1), Catalase (CAT, EC: 1.11.1.6), Peroxidase (POX, EC 1.11.1.7) and polyphenol oxidase (PPO, Ec 1.10.3.1) activities of Catharanthus roseus plants under field conditions. 10 mg l paclobutrazol, 5 µM gibberellic acid and 1 mg P. fluorescens concentrations were used for the treatments, and control plants were irrigated with well water. The treatments were given 38, 53, 68 and 83 days after planting (DAP) by soil drenching. The plants were taken randomly 45, 60, 75 and 90 DAP and separated into root, stem, leaves and flowers and used for estimating the antioxidant enzymes. The results showed that these plant growth regulators have significant effects on antioxidant enzymes of C. roseus.

We investigated the relative contributions of the environment and development stage on total polyphenols, flavonoids and condensed tannins contents, as well as 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide scavenging activities in four Tunisian Mentha pulegium. Shoot total phenolics and antioxidant capacities were significantly dependent on environment, development stage and their interaction. Environment effects were considerably larger than development stage effects for total phenolics, flavonoids, DPPH and superoxide scavenging capacities, whereas development stage was much stronger than environment for tannin content and, although small, interaction effects of the two factors (environment and development stage) were significant for all antioxidant properties analyzed. The highestantioxidant activities were related to high phenolic contents. Three behaviors were revealed; the best antioxidant capacities in Soliman at floral bud stage, followed by Takelsa and the lowest potentialities (Bouarada and Jdeida). These findings indicate that antioxidant properties of M. pulegium were respectively influenced by environment, development stage and their interaction.PRACTICAL APPLICATIONMentha pulegium L. belonging to the Lamiaceae family, which is a highly advanced and homogeneous family, is largely used in food preparation, perfumery, pharmaceutical products and as an insect repellent. In traditional medicine, M. pulegium essential oil is used for digestive, liver and gallbladder disorders, for gout colds and increased micturition and externally for skin diseases (Gruenwald et al. 1998). M. pulegium is a folkloric medicinal plant with interesting shoot antioxidant properties. According to our results, high antioxidant properties of the leaves of M. pulegium might be beneficial to the antioxidant activity.

In the past 20 years, the major effort in plant breeding has changed from quantitative to molecular genetics with emphasis on quantitative trait loci (QTL) identification and marker assisted selection (MAS). However, results have been modest. This has been due to several factors including absence of tight linkage QTL, non-availability of mapping populations, and substantial time needed to develop such populations. To overcome these limitations, and as an alternative to planned populations, molecular marker-trait associations have been identified by the combination between germplasm and the regression technique. In the present preview, the authors (1) survey the successful applications of germplasm-regression-combined (GRC) molecular marker-trait association identification in plants; (2) describe how to do the GRC analysis and its differences from mapping QTL based on a linkage map reconstructed from the planned populations; (3) consider the factors that affect the GRC association identification, including selections of optimal germplasm and molecular markers and testing of identification efficiency of markers associated with traits; and (4) finally discuss the future prospects of GRC marker-trait association analysis used in plant MAS/QTL breeding programs, especially in long-juvenile woody plants when no other genetic information such as linkage maps and QTL are available.

Reactive oxygen species (ROS) are produced in plants as byproducts during many metabolic reactions, such as photosynthesis and respiration. Oxidative stress occurs when there is a serious imbalance between the production of ROS and antioxidant defense. Generation of ROS causes rapid cell damage by triggering a chain reaction. Cells have evolved an elaborate system of enzymatic and nonenzymatic antioxidants which help to scavenge these indigenously generated ROS. Various enzymes involved in ROS-scavenging have been manipulated, over expressed or downregulated to add to the present knowledge and understanding the role of the antioxidant systems. The present article reviews the manipulation of enzymatic and nonenzymatic antioxidants in plants to enhance the environmental stress tolerance and also throws light on ROS and redox signaling, calcium signaling, and ABA signaling.