Physiological Mechanism of Nitrogen Mediating Cotton

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722 Physiological Mechanism of Nitrogen Mediating Cotton Gossypium hirsutum L Seedlings Growth. under Water Stress Conditions, wheat Shangguan et al 13 found that water use effi erance in cotton Gossypium hirsutum L seedlings. ciency decreased more with high N fertility than in. plants in a low N treatment due to a larger decrease in 2 Materials and Methods. photosynthetic rate than in transpiration rate Increasing. A pot experiment was conducted in a growth chamber. soil N supply decreased the growth of pearl millet Pen. Conviron PGR35 Conviron Winnipeg Canada at the,nisetumglaucum L R Br under soilwater deficit 14. University of Arkansas Altheimer Laboratory in Fayette. In recent years information has been accumulating on. ville USA Cotton Gossypium hirsutum L cultivar DPL. plant biochemical physiological morphological anato. 444B2R was planted on October 1 2007 The growth, mical and metabolic responses to waterlogging in wheat. chamber study was repeated at Nanjing Agricultural Uni. maize and winter rape 15 16 The adverse effects of wa. versity in Nanjing China using a similar transgenic cotton. terlogging on terrestrial plants are a complex phenomena. and appear to vary with genotype pretreatments plant cultivar NuCOTN33B planted on May 15 2008 When. developmental stage and the duration and severity of the cotton seedlings had two true leaves individual healthy. flooding Such inhibitory effects may occur due to the rapid and uniform plants were transplanted into 1 L pots 1 5 L. development of anoxic or hypoxic conditions in water pots in Nanjing China containing washed sand and nu. logged soils Considerably low amounts of oxygen in the trient solution In both experiments the growth chambers. root zone hampers root respiration resulting in a limited were set for a 12 h photoperiod with day night tempera. supply of energy required for nutrient uptake and trans ture of 30 C 20 C The experiment was arranged in a com. port 17 This nutrient deficiency ultimately detriment pletely random design with three treatments of water ma. tally disturbs a range of physiological processes such as nagement and three rates of applied N fertilizer Each treat. root stem and leaf growth stomatal closure photosyn ment had 9 replications where one pot with a single plant. thesis and respiration chlorosis and necrosis resulting in represented one replication. premature leaf senescence and increased susceptibility to Three water treatments included 1 a well watered. diseases in plants subjected to waterlogged conditions control WW water utilization was 66 7 ml day 1 plant 1. 18 19 In addition some oxygen dependent biochemi 2 a drought stressed treatment DS the water utilization. cal substances such as cytochromes oxidasesanddesatu was 33 3 ml day 1 plant 1 and 3 a waterlogged treat. rases were damaged Zaidi et al 20 showed that the early ment WL with 2 3 cm water layer in the washed sand. stages of maize development were the most sensitive to surface for 10 days after the seedlings were transplanted. waterlogging Waterlogging for 6 days caused most of into pots The cotton seedlings were waterlogged when. the roots except for some adventitious roots to decom the 5th leaf had emerged and the seedlings were allowed. pose and plants were unable to take up the required at to recover on the evening of the 10th day with a water. mospheric and edaphic nutrients resulting in leaching regime similar to the well watered control Water status. and denitrification and finally in N deficiency was monitored every three days by weighing the pots and. Nitrogen supply and use are the most effective regula then watering the plants accordingly Three N rates were. tory factors in crop growth and yield formation even used Table 1 132 2 mg N pot 1 LN 16 mM approxi. under stress condition such as drought and waterlogging mately 224 mg N l 1 water 246 4 mg N pot 1 MN 24. Nitrogen also enhanced sucrose synthase activity in wheat mM approximately 448 mg N l 1 water and 369 6 mg. grain under water deficit during grain filling Application N pot 1 HN 32 mM approximately 672 mg N l 1 water. of N has been reported to partially alleviate the damage respectively The total N was incorporated into the pots. of waterlogging in maize corn and barley plants 8 21 before waterlogging The other ingredients of the Hoag. 22 and increase the biomass of maize 23 However it lands nutrition solutions were the same When the 5th 6th. is not known whether nitrogen supply could pay a similar and 7th main stem leaves of the cotton seedlings had. role in cotton subjected to seedlings waterlogging emerged the second third and fourth main stem leaves. Nitrogn metabolism protein synthesis and antioxidant respectively which had been labeled were sampled for. metabolism are important plant growth indicators which analysis. related to crop yield formation which have been reported The net photosynthetic rate Pn of labeled leaves were. on drought and waterlogging in the cotton root at the measured with a photosynthesis system Li 6200 Li COR. flowering and boll forming stage 24 However infor Inc Fayetteville Li 6400 Li COR Inc Nanjing under. mation of the effect of N on physiological changesunder 800 mol m 2 s 2 light intensity at 9 30 11 00 am Photo. water stressin cotton seedlings is not documented yet It synthesis measurements were taken on the fourth fully. is still unclear whether N plays a positive role in allevi expanded main stem leaf four nodes from the terminal. ating the adverse effects of water stress on the growth of After measurement of photosynthesis three seedlings. cotton seedlings Therefore the objective of this investi from each treatment were cut at the cotyledonary node. gation was to study the effects of N on water stress tol The roots were separated from the sand by washing and. Copyright 2012 SciRes AJPS, Physiological Mechanism of Nitrogen Mediating Cotton Gossypium hirsutum L Seedlings Growth 723. under Water Stress Conditions, Table 1 The concentration of nutrient solutions used for the N treatments.
Treatment N K Ca Mg P S Fe,mM mM mM mM mM mM g l 1. LN 16 0 4 0 1 5 1 0 2 0 1 0 5 0,MN 24 0 4 0 1 5 1 0 2 0 1 0 5 0. HN 32 0 4 0 1 5 1 0 2 0 1 0 5 0, samples of 0 5 g of white young root were immediately at 532 nm and 600 nm Measurement of soluble protein. used to assay root activity The labeled leaveswere stored content was according to the method of Zhang 26 using. at 70 C for subsequent enzyme activity analysis The 1000 ml G 250 mixture containing 100 mg coomassie. remaining leaves were collected to measure leaf area brilliant blue G 250 50 ml 90 grain alcohol and 100 ml. with a portable area meter Li 3000 A Li COR Inc Fa 85 W V phosphoric acid 1ml enzyme extract was in. yetteville Li 3100 Li COR Inc Nanjing after which jected in 5 ml G 250 mixture The test tubes were shaken. leaves stem and branches were dried in an oven to a con for 2 minutes and the absorbance of the reaction mixture. stant weight and the biomass and the biomass per unit was measured at 595 nm. area were determined After enzyme activity analysis the Measurement of root vigor was according to the tri. soluble sugar and amino acid were measured by utilizing phenyltetrazolium chloride TTC method 25 The sur. the remaining tagged leaves and the C N ratio was deter face moisture on the white young roots was blotted with. mined tissue paper and their fresh weights were measured. For determination of soluble protein content antioxi Roots with weights 0 5 g were placed in tubes filled. dant enzyme activity and malondialdehyde MDA con with 5 ml of 0 4 triphenyltetrazolium chloride TTC 5. tent frozen leaves segments 0 3 g were crushed into ml phosphate buffer 0 06 mol L 1 pH 7 0 The tubes. fine power in a mortar in an ice bath and 5 0 ml of 0 05 were incubated at 37 C for up to 3 hours The chemical. mol L 1 phosphate buffer pH 7 8 with 1 polyvinylpy reaction was stopped by adding 2 ml of 1 mol L 1 sulfu. rrolidone PVP was used as an extraction buffer The ric acid in the tubes This step was followed by extraction. homogenate was centrifuged at 15 000 rpm for 15 min with triphenyl formazan TPF which consisted of taking. utes at 4 C then the liquid was used to measure antioxi the roots out of the tubes and placing them in a pestle. dant enzyme activities MDA content and soluble protein filled with 3 4 ml of ethyl acetate and a little quartz. content sand and grinding The liquid phase was removed into a. Superoxide dismutase SOD activity was assayed ac test tube and ethyl acetate was added to the 10 ml level. cording the method of Li 25 One unit of SOD activity and OD values recorded with a UV Vis recording spec. was defined as the amount of enzyme required to cause trophotometer at 485 nm The OD values were used to. 50 inhibition of nitro blue tetrazolium NBT reduction calculate equivalent TPF concentrations with which the. measured with a UV Vis recording spectrophotometer root activity was determined for each fresh root weight as. UV 2401 Shimadzu Corporation Japan at 560 nm follows. Catalase CAT activity was determined by potassium Root vigor TPF g g 1FW hour 1 TPF reduction. permanganate titration The action mixture contained 2 9 g fresh weight g time hour. ml of 50 mM phosphate buffer pH 7 0 1 0 ml 10 mM All measurements were carried out with three repli. H2O2 and 100 l enzyme extract in tubes Peroxidase cates Statistical analysis was performed using the GLM. POD activity was analyzed in 2 9 ml of 0 05 mol L 1 analysis of variance from the SAS Institute 27. phosphate buffer containing 1 0 ml of 0 05 mol L 1 guai. acol and 1 0 ml 2 H2O2 The increase in absorbance at 3 Results. 470 nm was recorded after adding 2 0 ml 20 chloroace. 3 1 Growth of Cotton Seedlings, tic acid All the above procedures of enzyme extraction. were carried out at 0 C 4 C Measurement of MDA Plant height of the WW plants was higher than that of the. content was according to the method of Zhang 26 using WS and DL treatments and the DL plants were taller. 500 ml TCA TBA basic mixture containing 101 25 g than WS plants Table 2 The effects of N application. chloroacetic acid TCA and 2 5 g thiobarbituric acid on plant height of the DS treatment wasnon significant p. TBA 1 ml enzyme extract was injected in 4 ml TCA 0 05 while in WS plants the effect was highest in HN. TBA basic mixture Then the reaction mixture was incu and lowest in LN Plant height showed a rapid recovery. bated in boiling water for 20 minutes After cooling the in the WS treatment Application of N especially HN and. reaction mixture was centrifuged at 4000 g for 10 min MN helped to increase the plant height of the waterlogged. utes The absorbance of supernatant liquid was measured WS treatment The effects of the three water treatments. Copyright 2012 SciRes AJPS, 724 Physiological Mechanism of Nitrogen Mediating Cotton Gossypium hirsutum L Seedlings Growth.
under Water Stress Conditions, Table 2 Growth parameters of cotton seedlings in Fayetteville 2007 and Nanjing 2008. Plant height Biomass Leaf biomass per unit area,Water treatments N rates. DAT 22 DAT 29 DAT 36 DAT 22 DAT 29 DAT 36 DAT 22 DAT 29 DAT 36. cm g seedling mg cm,LN 8 7b1 15 3b 20 8b 0 8b 1 5b 2 5b 2 5 4a 6 3a. MN 9 7a 17 7a 23 5a 1 3a 2 3a 3 0a 5 4a 5 6b,HN 9 7a 16 7a 22 0a 0 6b 1 6b 2 7b 5 8a 5 9b. Mean 9 4 16 6 22 1 0 7 1 8 2 7 5 5 5 9,LN 10 5a 12 3a 14 5a 0 7a 1 2a 1 8a 5 5a 5 9a.
MN 10 2a 11 8a 14 5a 0 6b 1 1a 1 5a 5 8a 5 4a,Fayetteville DS. HN 9 9a 11 0a 14 3a 0 5c 1 1a 1 6a 5 7a 5 7a,Mean 10 2 11 7 14 4 0 6 1 1 1 6 5 7 5 7. LN 11 2a 11 6a 13 1a 0 7a 1 2a 1 6a 5 5c 5 6c,MN 9 5b 9 7b 12 3a 0 6b 0 8b 1 6a 7 0a 7 7a. HN 7 9c 8 3c 10 5b 0 5c 0 6b 1 3a 6 0b 6 4b,Mean 9 5 9 9 12 0 0 6 0 9 1 5 6 2 6 6. LN 10 5b 16 7a 21 1b 1 2b 2 3b 3 2b 4 4a 5 6a,MN 12 6a 18 5a 26 3a 1 8a 3 4a 5 3a 4 1a 4 9b.
HN 13 1a 19 3a 27 0a 1 8a 2 8b 5 0a 4 8a 5 1b,Mean 12 1 18 2 24 8 1 6 2 8 4 5 4 4 5 2. LN 9 6a 14 7a 18 1a 0 9a 1 8a 3 0b 4 9b 4 8b,MN 10 1a 15 2a 17 5a 1 2a 2 1a 3 2b 5 5a 5 6a. Nanjing DS,HN 10 0a 15 8a 18 3a 0 7b 1 9a 4 1a 4 7b 4 5b. Mean 9 9 15 2 18 0 9 1 9 3 4 5 0 5 0,LN 8 4c 10 5a 14 1a 1 1a 1 5a 2 1a 3 2b 4 1b. MN 11 1a 11 0a 13 7a 1 2a 1 7a 2 0a 4 6a 5 3a,HN 9 9b 8 1b 9 5b 0 5c 0 9b 1 5b 3 5b 4 4b.
Mean 9 8 9 9 12 4 0 9 1 4 1 9 3 8 4 6, Means followed by the same letters within the column for each location are not significantly different at p 0 05 2data not recorded. on plant biomass was similar to the effects on plant nitrogen level LN generally increased the soluble pro. height with WS the lowest and WW the highest Table tein content. 2 Increasing application of N helped to increase the. biomass per plant in the DS and WL treatments espe 3 3 Antioxidant Enzyme Activity. cially during the water stressed stage Specific leaf weight. There were differences in antioxidant enzymes activities. leaf biomass per unit area increased p 0 05 in the WS. among the three water treatments Table 4 and these. treatment compared to the WW and DS treatments Ta, differences changed according to the sampling date Ap. ble 2 but there was no difference between WW and DS. plication of N played a significant role in adjusting the. treatments Nitrogen application did not change the leaf. antioxidant enzymes activities The SOD activity was at. biomass per unit area of DS however increasing appli. DAT 22in the DSS treatment and lowest in the WLS, cation of N helped increase the leaf biomass per unit area. Physiological Mechanism of Nitrogen Mediating Cotton Gossypium hirsutum L Seedlings Growth under Water Stress Conditions Zhigou Zhou 1 2 Derrick M Oosterhuis 2 1Key Laboratory of Crop Physiology amp Ecology in Southern China of Ministry of Agriculture Nanjing Agricultural University Nanjing

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