[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.
Journal of Plant Physiology 08/2009; 167(1):1-9. · 2.77 Impact Factor
[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.
Journal of Agronomy and Crop Science 02/2009; 195(3):213 - 224. · 2.62 Impact Factor
[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 50mM NaCl (sublethal
dose) for 7days followed by half strength Hoagland solution containing 100mM NaCl (lethal dose) for another 7days. The
non-pretreated 29days old rice seedlings maintained in half strength Hoagland solution were directly transferred to half
strength Hoagland solution containing 100mM NaCl (lethal dose) solution for 7days. 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.
Plant and Soil 01/2006; 284(1):363-373. · 3.24 Impact Factor
[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.
[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.
[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: 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 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.
[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.