[Show abstract][Hide abstract] ABSTRACT: Field studies were conducted from 2002 to 2005 to evaluate foliar spray of Atonik (a plant growth regulator (PGR) containing nitrophenolates) on cotton boll abscission rate by assessing various reactive oxygen species (ROS) contents, antioxidant content and antioxidant enzyme activity from 1 to 9 days after anthesis (DAA). The result indicated that the nitrophenolate spray reduced hydrogen peroxide (H(2)O(2)), superoxide anion (O(2)(-)) accumulation, lipid peroxidation (malondialdehyde--MDA), lipoxygenase (LOX) activity and membrane permeability relative to the control. Antioxidant enzyme activity (superoxide dismutase, SOD; ascorbate peroxidase, APX; peroxidase, POX; glutathione peroxidase, GSH-Px) was significantly increased by the nitrophenolate spray. The POX (217%) and GSH-Px (242%) activities were enhanced compared with APX (7.7%) activity at 9 DAA. Enhanced accumulation of ascorbate (245%), phenol (253%) and proline (150%) was observed in nitrophenolate-sprayed plants compared with control at 9 DAA. Because ascorbate content is increased by higher dehydroascorbate reductase (DHAR) enzyme activity, the ascorbate was able to replenish reducing equivalents to phenoxyl radicals, resulting in an increase of phenolic compounds. The increased phenolic acid content may be involved in scavenging the ROS produced in developing cotton boll. The role of DHAR and glutathione reductase (GR) in keeping higher levels of reduced ascorbate and low levels of endogenous H(2)O(2) in the developing cotton boll may be the prerequisite for boll retention. Based on the present work, we conclude that nitrophenolate-sprayed plants counteracted the deleterious effects of ROS by the peroxide/phenolics/ascorbate system, which causes reduced boll abscission and increased yield.
Full-text · Article · Aug 2009 · Journal of Plant Physiology
[Show abstract][Hide abstract] ABSTRACT: Leaf senescence is an oxidative process, and most of the catabolic processes involved in senescence are propagated irreversibly once initiated. An experiment was conducted to test the hypothesis that nitrophenolates (Atonik, a plant growth regulator) spray can delay the leaf senescence through reduced oxidative damage. Atonik 3.75 g a.i. ha−1 was sprayed during boll filling stage on cotton, and the senescence process was evaluated by quantifying total chlorophyll contents, photosynthetic rate, Fv/Fm ratio, various reactive oxygen species (ROS) content, antioxidant content and antioxidant enzyme activity from 90 days after sowing (DAS) to 130 DAS. The result indicated that nitrophenolate spray reduced the hydrogen peroxide (H2O2), superoxide anion (O2−) accumulation, lipid peroxidation (malondialdehyde), lipoxygenase activity and membrane permeability over unsprayed control. The antioxidant enzyme activity (superoxide dismutase, SOD; ascorbate peroxidase, APX; peroxidase, POX; glutathione peroxidase, GSH-Px) were significantly increased by the nitrophenolate spray. POX (118.1 %) and GSH-Px (143.3 %) activities were enhanced to a higher level compared to APX (8.5 %) activity at 130 DAS. Enhanced accumulation of ascorbate (144.9 %), phenol (154.7 %) and proline (50 %) was seen in nitrophenolate-sprayed plants compared with unsprayed control plants at 130 DAS. Ascorbate content is increased by higher dehydroascorbate reductase enzyme activity. Ascorbate was thus able to replenish reducing equivalents to phenoxyl radicals resulting in an increase in phenolic compounds. The increased phenolic acid content may be involved in scavenging the ROS produced during senescence process. The higher level of reduced ascorbate and low level of endogenous H2O2 in the leaves may be the prerequisite for delayed leaf senescence in the nitrophenolate-sprayed plants. Based on the present work, it can be concluded that nitrophenolate-sprayed plants can postpone the leaf senescence by peroxide/phenolic/ascorbate system which is involved in scavenging the ROS produced during leaf senescence.
No preview · Article · Feb 2009 · Journal of Agronomy and Crop Science
[Show abstract][Hide abstract] ABSTRACT: The physiological ability to adapt for various environmental changes is known as acclimation. When exposed to sublethal level of stress, plants develop the ability to withstand severe stress, as acquired tolerance. The present study was conducted to explicate the physiological basis of acquired tolerance in rice. Rice seedlings (variety IR 20) were grown in half strength Hoagland solution, and after 22nd day, they were kept in half strength Hoagland solution containing 50 mM NaCl (sublethal dose) for 7 days followed by half strength Hoagland solution containing 100 mM NaCl (lethal dose) for another 7 days. The non-pretreated 29 days old rice seedlings maintained in half strength Hoagland solution were directly transferred to half strength Hoagland solution containing 100 mM NaCl (lethal dose) solution for 7 days. The control plants were maintained in half strength Hoagland solution without NaCl. Various morphological and physiological parameters were recorded on 29th and 36th days old seedlings from control, pretreated and non-pretreated plants. The results revealed significant reduction in growth parameters (shoot length, root length, leaf area and total dry matter production) of non-pretreated plants below that of pretreated plants. The pretreated plants showed increased values to the extreme of 19.8 per cent in leaf water potential (ψw), 9 per cent in relative water content (RWC), 26 per cent in photosynthetic rate (P
N), 28 per cent in leaf stomatal conductance, and 47 per cent in chlorophyll a over non-pretreated plants. The same trend was also observed in chlorophyll a/b ratio (6.6%) and F
m ratio (19.3%). However, a reverse trend was seen in F
o value. The pretreated plants showed improved ionic regulation as evident from low Na+, Cl− and high K+ contents, which is attributed to enhanced plant water status and photosynthesis. Both pretreated and non-pretreated plants had higher contents of osmolytes viz., sucrose, leaf soluble sugars and proline contents than control plants. However, starch content revealed an inverse trend. Therefore, the present study reveals that rice can acclimate to lethal dose of salinity stress by pretreatment with sublethal dose of NaCl.
[Show abstract][Hide abstract] ABSTRACT: Selenium (Se) is regarded as an antioxidant in animals and plants, even though considered as non-essential element in plants. To test its ability to counteract senescence related oxidative stress in soybean a pot culture experiment was conducted. The soybean plant was sprayed with sodium selenate (50 ppm) at 78 days after sowing (DAS). Soybean leaves were harvested at 80 and 90 DAS for analysis of oxidant production and antioxidative enzymes activity. Se positively promoted growth and acted as antioxidant by inhibiting lipid peroxidation and per cent injury of cell membrane. The antioxidative effect was associated with an increase in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes activity. Significant increase in antioxidant enzyme activity was positively related to Se content. The decrease in antioxidative enzymes at 90 DAS was much faster in control plants than Se-sprayed plants. The reduction in SOD and GSH-Px may be associated with senescence-induced oxidative burst.
[Show abstract][Hide abstract] ABSTRACT: A lab experiment was conducted to evaluate the effect of Atonik as seed treatment on germination, establishment, growth and various biochemical parameters of cotton and tomato. Seed treatment of Atonik at 3 ppm in both cotton and tomato was found to be best in recording maximum germination, establishment and enzyme activity on concentration basis. The increase in seedling physiological parameters may be correlated with internal auxin content.
Full-text · Article · Feb 2005 · Journal of Biological Sciences
[Show abstract][Hide abstract] ABSTRACT: A field experiment was conducted in cotton during 2002-2003, in the experimental field of Tamil Nadu Agricultural University, to study the response of cotton plant to Atonik (a nitrophenolic compound) and TIBA in combination and as individual treatment. The plants were sprayed with Atonik and TIBA at 0.25% and 100 ppm during flowering and boll set stages. The results revealed that application of Atonik increased the growth parameters viz., plant height and leaf area, while TIBA reduced it. In combination the effect of TIBA on morphological characters has been reverted by Atonik spray. Catalase, peroxidase and superoxide dismutase enzyme activity were increased by Atonik spray, whereas TIBA decreased the enzyme activity. The treatment combination of Atonik and TIBA resulted in a better performance than control. Both TIBA and Atonik increased the yield per plant over control. The yield increase was mainly due to increase in more number of bolls per plant.
Full-text · Article · Feb 2005 · Journal of Biological Sciences
[Show abstract][Hide abstract] ABSTRACT: Leaf leachate of Eucalyptus globulus was evaluated for alleopathic effect on rice, sorghum and blackgram. Leaf leachate was tried at 5, 10 and 20% concentrations. Seed germination, shoot length, seedling dry matter and vigour index were significantly reduced by leaf leachate and highest inhibition was observed in 20% concentration. The magnitude of inhibition followed the order of blackgram > rice > sorghum. Germination and root length was inhibited to a tune of 18.6 and 75.8, and 14.7 and 60.0% for blackgram and sorghum, respectively at 20% concentration. The leaf leachate application also influenced the metabolism of seedlings viz., chlorophyll a, b and total chlorophyll, soluble protein, proline and phenol content. In general, leaf leachate increased the proline and phenol content, and decreased the chlorophyll and soluble protein contents, in all the test crops over control. Among the parameters studied, proline was found to be associated with higher seedling growth of rice (200% increase over control), blackgram (94% increase over control) and sorghum (183% increase over control).
[Show abstract][Hide abstract] ABSTRACT: A field investigation was conducted on cotton during 2002-2003 at Tamil Nadu Agricultural University, Coimbatore, India to study the influence of Atonik (nitro phenolic compound) on quality improvement in cotton var. MCU 12. The quality parameters viz., fibre length, uniformity ratio, fibre fineness, bundle strength and elongation ratio was significantly influenced by Atonik treatments. Among the stages of application, Atonik applied during square formation, flowering and boll set stages was found to be superior, followed by application during flowering and square formation stages. Among the concentrations used, application of Atonik at 0.25% was found to be highly effective in increasing all the quality attributes. Increased fibre length in Atonik treated plants (0.25%) may be attributed to the increased internal auxin pool or due to modulation in the turgor of cell wall altered by cell elasticity, as it is the mode of action of auxin.
Full-text · Article · May 2004 · Asian Journal of Plant Sciences
[Show abstract][Hide abstract] ABSTRACT: A field investigation was conducted on tomato and cotton during 2002-2003 at Tamil Nadu Agricultural University, to study the harvest time residue of Atonik (nitro phenolic compound) in soil, leaf and fruit/boll. The mean recovery percent of various constituents of Atonik ranged between 85-97%. The harvest time residual level was found to be below detectable limit and it is safe for consumption. The applied nitrophenols may be degraded by various microorganisms by providing carbon and nitrogen sources or by photo oxidation.
Full-text · Article · May 2004 · Asian Journal of Plant Sciences
[Show abstract][Hide abstract] ABSTRACT: An experiment was conducted to study the effect of selenium on senescence phenomenon in soybean. Selenium was applied both as seed treatment at 5 ppm and as foliar spray at 50 and 100 ppm on 45, 60 and 75 DAS. The impact of selenium on delaying senescence was well established by increased activity of antioxidant enzymes such as, catalase and peroxidase and more numbers of leaves. Improved source strength by retaining more leaf number and area with better partitioning efficiency was considered as the contributing factor for significant yield improvement in selenium-treated plants.
No preview · Article · Apr 2004 · Journal of Food Agriculture and Environment
[Show abstract][Hide abstract] ABSTRACT: The rice plant at any point in time is composed of leaves of physiologically different ages, so it follows that the leaves differ in their contributions to the growth of the whole plant and its grain yield. As the leaf chlorophyll content (Soil Plant Analytical Division value) is the best indicator of photosynthetic activity in rice, the chlorophyll content of rice before and after flowering was determined in a weed management field experiment on direct wet seeded rice. The results indicated that the leaf chlorophyll content at 79 days after sowing correlated well with the grain yield of rice. Multiple regression models also indicated the dependence of rice yield on leaf chlorophyll content before and after flowering.
Chlorophyll Dynamiken bei Reis (Oryza sativa) vor und nach der Blüte basierend auf SPAD (Clorophyll) – meter-monitoring und seine Bedeutung für den Kornertrag
Reispflanzen weisen während ihrer Lebensdauer Blätter physiologisch unterschiedlichen Alters auf; dies läßt vermuten, dass die Blätter unterschiedliche Beiträge zum Wachstum der Gesamtpflanze und des Kornertrages leisten. Der Blattchlorophyllgehalt (SPAD-Wert) ist der beste Indikator der photosynthetischen Aktivitäten bei Reis; Untersuchungen des Chlorophyllgehaltes bei Reis vor und nach der Blüte in einem Feldexperiment mit Unkrautbekämpfung und direkten Wasseraussaat wurden durchgeführt. Die Ergebnisse weisen darauf hin, dass der Blattchlorophyllgehalt zum 79 DAS mit dem Kornertrag von Reis korreliert ist. Multiple Regressionsmodelle weisen ferner darauf hin, dass eine Abhängigkeit des Reisertrages vom Blattchlorophyllgehalt vor und nach der Blüte besteht.
Full-text · Article · Mar 2002 · Journal of Agronomy and Crop Science