Roles of plant growth regulators on yield, grain qualities and antioxidant enzyme activities in super hybrid rice (Oryza sativa L.)
- Shenggang Pan†1, 2,
- Fahd Rasul†1, 3,
- Wu Li1, 4,
- Hua Tian1, 2,
- Zhaowen Mo1, 2,
- Meiyang Duan1, 2 and
- Xiangru Tang1, 2Email author
© Pan et al.; licensee Springer. 2013
Received: 3 December 2012
Accepted: 11 April 2013
Published: 16 April 2013
Plant growth regulators play important roles in plant growth and development, but little is known about roles of plant growth regulators in yield, grain qualities and antioxidant enzyme activities in super hybrid rice. In this study, gibberellic acid(GA3), paclobutrazol (PBZ), 6-Benzylaminopurine(6-BA) treatments and distilled water (control) were sprayed to two hybrid rice cultivars (Peizataifeng and Huayou 86) at the heading stage in the field experiments in both early and late season in 2007. Treatments were arranged in a split-plot design with four replications. Cultivars treatments with two newly developed super hybrid rice Peizataifeng and Huayou86 were the main plots and plant growth regulators treatments were the subplots. Subplot treatments included (1) plots sprayed with distilled water(CK), (2) plots sprayed with 20 mg L-1 GA3 prepared using 95% ethanol as surfactant(GA3), (3) plots sprayed with 50 mg L-1 PBZ(PBZ), (4) plots sprayed with 30 mg L-1 6-BA(6-BA).
Spraying PBZ with 50 mg L-1 or 6-BA with 30 mg L-1 at the heading stage could increase the number of spikelets per panicle, seed setting rate and grain yields in Peizataifeng and Huayou86 in both seasons. PBZ treatment also significantly improved head rice rate and amylose content in Peizataifeng and Huayou86 in early season. Furthermore, it was observed that spraying PBZ or 6-BA could increase super oxide dismutase (SOD) and peroxidase (POD) activities, decrease accumulation of malendialdehyde (MDA) in flag leaves at the late growth stage.
Application of PBZ or 6-BA partially alleviated the detrimental effects of rice senescence by modulating the activity of enzymatic antioxidants, and improving antioxidant system, which helped in sustaining plant growth. Therefore, spraying PBZ with 50 mg L-1 or 6-BA with 30 mg L-1 at the heading stage could increase grain yields and improve grain qualities in the two super hybrid rice.
KeywordsExogenous hormone Protective enzyme Rice (Oryza sativa L.)
Rice is the most important staple food in Asia, providing average 32% of total calorie uptake (Maclean et al., 2002). Mainly because of a still-growing population, demand for rice is expected to keep increasing in the coming decades (Pingali et al., 1997). At the current growth of population rice requirement increases dramatically and many nations are facing second-generation challenge of producing more rice at less cost in a deteriorating environment. Thus, improved technologies are required to achieve the goal of ensuring food security which is a challenging task. Therefore, enhancing productivity of rice through novel genetic approaches and exogenous plant growth regulators will be necessary.
Rice hybrids with a yield advantage of 20% were developed in China in the 1970s and are now planted in about 57% of the rice area in the country (Yuan, 2011). Plant growth regulators play vital roles in coordination of many growth and behavioral processes in rice, which regulates the amount, type and direction of plant growth (Rajendra and Jones Jonathan 2009; Anjum et al., 2011). The use of plant growth regulators, as GA3, PBZ, 6-BA or their compounds, is becoming popular to ensure efficient production. Remarkable accomplishments of plant growth regulators such as manipulating plant growth and crop yield have been actualized in recent years (Sarkar et al., 2002; Sakamoto et al.,2005; Morinaka et al., 2006; Yan et al., 2011; Zvi and Eduardo 2011). Plant growth regulators modify growth and development in various ways under different growth conditions. GA3 is responsible for stimulating the production of mRNA molecules in the cells, which in turn improves the chances of fast growth (Richards et al., 2001; Olszewki and Gubler 2002; Emongor, 2007). Nonstructural carbohydrates (NSC) and crude protein (CP) contents in rice straw were significantly increased by spraying GA3, especially on the 15th d after anthesis, and the fermentation quality of rice straw silage was improved with the increase of NSC and CP contents. Single panicle weight was also significantly increased by spraying GA3 after anthesis (Dong et al., 2012). Priming with GA3 was very effective in improving salinity-induced decrease in number of grains per ear on main stem in both wheat cultivars, which can alter the uptake and pattern of accumulation of different ions between shoots and roots in the adult plants of wheat under saline conditions. PBZ is a member of the triazole plant-growth inhibitor group. Like many plant growth regulators, triazoles have plant growth regulatory effects. Triazoles also increase tolerance of various plant species to biotic and abiotic stresses, including fungal pathogens, drought, air pollutants, and low and high temperature stress, by reducing oxidative damage via elevation of antioxidants or reducing the activity of oxidative enzymes (Lin et al., 2006; Baninasab Bahram, 2009). PBZ normally is applied as a foliar spray (Still and Pill, 2004). As one kind of cytokinin, 6-BA can reduce ethylene sensitivity of cut flowerers (Yuan et al., 2012). Exogenous 6-BA is able to inhibit the effects of ethylene, inhibit ethylene biosynthesis, induce 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene expression and is involved in the early regulation of ethylene signal transduction in plants(Hall et al., 2001; Gapper et al., 2005). Zhang et al. (2007) reported that spraying external 6-BA on the leaves at late growth period of the late-season rice could increase seed setting rate and grain yield by delaying leaves senescence.
Two new super hybrid rice, Peizataifeng and Huayou86, were developed by College of Agriculture, South China Agricultural University (SCAU). Peizataifeng (Peiai64S × taifengzhan), which is a two-line hybrid rice. Its whole growth period is about 125 and 115 days for early and late planting in southern area of China, respectively. Huayou86 is the new combination of late maturity-temperate three-line hybrid rice which has growth period of 130 days for early growing season and 115–120 days for late growing season in southern China, respectively. These two varieties have become important and popularized because of better growth characteristics in recent years (Jiang, 2008).
Published data have addressed effects of different plant growth regulators on rice growth and development (Yang et al., 2000; Bahram 2009; Yan et al., 2011). However, Southern China is one of the biggest double rice areas in China. Peizataifeng and Huayou86 are the important popularized varieties in Southern China. Knowledge of plant growth regulation on these two newly developed rice hybrids is quite less in regional and international scientific literature. Therefore, the purpose of this study was to investigate the comparative effects of plant growth regulators (GA3, PBZ and 6-BA) on yield, grain quality and antioxidant enzyme activities in super hybrid rice.
Grain yield and its components
Effects of plant growth regulators on yield and its components of cultivars of Peizataifeng and Huayou 86 in both early and late seasons in 2007
Panicle number (m-2)
No. of Spikelets per panicle
Grain filling percentage (%)
Yield (kg ha-1)
2007 early rice
2007 late rice
Higher grain yield under GA3, PBZ and 6-BA treatments was mainly ascribed to the significant higher spikelets per panicle and grain filling percentage (Table 1). On average, grain yield of Huayou 86 was higher than that of Peizataifeng. Average grain yield was higher in late season than that in early season.
Effects of plant growth regulators on brown rice rate, milled rice rate, head rice rate, chalkiness and amylose content of cultivars Peizataifeng and Huayou 86 in both early and late seasons in 2007
Brown rice (%)
Milled rice (%)
Head rice (%)
Amylose content (%)
2007 early rice
2007 late rice
Anti-oxidant enzyme activities
The same trend appeared for both cultivars Peizataifeng and Huayou 86 during late growing season. MDA value in flag leaves of cultivar Peizataifeng for CK ranged from 2.31 μmol g-1 to 8.73 μmol g-1 at 7, 14 and 21DAH, while those for treatments PBZ and 6-BA decreased from 1.95 μmol g-1 to 6.07 μmol g1, and 1.93 μmol g-1 to 6.68 μmol g-1, respectively. The leaf MDA contents of all treatments started to increase progressively with the passage of time until 21 DAH after which MDA contents became almost stable. Overall, higher leaf MDA contents were observed for Peizataifeng than for Huayou 86 depicting a genotypic difference for leaf MDA contents. Seasonal variation was also evident from the MDA contents values as average MDA contents were comparatively high at the late growing season when compared with the early growing season.
Plant growth regulators (GA3, PBZ and 6-BA) play important roles in plant growth, development, yield and qualities formation (Ekamber and Kumar 2007; Rajendra and Jones Jonathan 2009). Zheng et al. (2011) found that suitable application of plant growth regulators (such as NAA-Na,GA3 or 6-BA) could improve the photosynthetic capacity, delay the leaf senescence and promote the rate of rice seed-setting.In this study, we observed that spraying PBZ with 50 mg L-1 or 6-BA with 30 mg L-1 at the heading stage could also increase number of spikelets per panicle, seed setting rate and grain yields in both cultivars of Peizataifeng and Huayou 86 in both seasons. There was more noticeable effect on yield in Huayou 86 than in Peizataifeng with foliar application of PBZ or 6-BA. This result agrees with the findings of Peng et al. (2011), who found that spraying PBZ in rice had more effective grain number, seed setting rate, 1000-grain weight, and yield was increased by 11.89% under PBZ treatment compared with the CK. Furthermore, the application could enhance the lodging resistance and obviously increase root biomass and root activity to improve phosphorus and potassium accumulation in rice stem, leaves and grains. SOD and POD are important antioxidant enzymes that detoxify active oxygen species. Antioxidant enzymes aid cells in removing harmful oxygen species. We also found that spraying PBZ or 6-BA could increase SOD and POD activities, and decrease accumulation of MDA in flag leaves at the late growth stage. This result suggested that PBZ or 6-BA application partially alleviated the detrimental effects of rice senescence by modulating the activity of enzymatic antioxidants, improving antioxidant system, which helped in sustaining plant growth and yield.
Grain quality is one of the most important traits in evaluating planting rice’s benefit. There were significant effects on grain qualities by spraying exogenous plant growth regulator. Du et al. (2010) studied that the inferior grains plumpness in rice was enhanced 9.7% and 5.5% by spraying exogenous 6-BA and GA3 at 5 days before flowering, respectively. Application of 6-BA decreased the chalky rice rate and chalky area of grain and chalk degree compared to the CK, respectively. Furthermore, exogenous hormones had greater effects on grain qualities of inferior spikelets than superior spikelets. Dong et al. (2009) reported that the effects of exogenous hormones on rice quality varied with exogenous hormone varieties and different grain positions by spraying GA3 (57.7 μmol -L) at earlier filling stage in rice. The exogenous GA3 decreased 1000-grain-weight and head rice rate and protein content, but increased chalkiness and amylose content. In present study, the effect of spraying GA3 on 1000-grain-weight and head rice rate of the earlier-flowered spikelets was greater than that of the later-flowered spikelets. PBZ treatment significantly increased head rice rate and amylose content in the cultivars Peizataifeng and Huayou86 in early season, however, the chalkiness of grains was not increased significantly. Our results did not agree with previous studies fully (Dong et al., 2009). Variations may have arose due to experimental materials, plant growth regulator concentration and application time. It is, therefore, possible that foliar plant growth regulator could be a useful tool in promoting grain yield and bettering quality in rice. Whether or not this would be sufficient to promote adequate rice production for the whole cycle would require further more detailed and longer-term investigation in the aspects of a diverse group of rice genotypes and physiological and biochemical mechanism arising from plant growth regulator’s influence.
Spraying PBZ with 50 mg L-1 or 6-BA with 30 mg L-1 at the heading stage could increase spikelets per panicle, seed setting rate and grain yields in the cultivars Peizataifeng and Huayou 86 in both seasons. PBZ treatment also significantly improved head rice rate and amylose content in two cultivars of Peizataifeng and Huayou 86 in early season. Furthermore, it was observed that spraying PBZ or 6-BA could increase SOD and POD activities, decrease accumulation of MDA in flag leaves at the late growth stage. Application of PBZ or 6-BA partially alleviated the detrimental effects of rice senescence by modulating the activity of enzymatic antioxidants, improving antioxidant system, which helped in sustaining plant growth.
Field experiments were conducted in the early season (March-July) and repeated in the late season (July to November) in 2007, at the College of Agriculture’s Experimental Farm, South China Agricultural University (SCAU), Guangzhou, Guangdong province, China (113.18′E, 23.10′N, elevation 18 m). The properties of soil collected from the upper 20 cm are as follows, 22.0 g kg-1 organic C, available N 105.7 mg kg-1, available P 128.3 mg kg-1(water as extract), available K 112.5 mg kg-1(ammonium acetate(1 mol l-1) as extract).
Treatments were arranged in a split-plot design with four replications. Main plots were varieties with two newly developed super hybrid rice Peizataifeng and Huayou86. Peizataifeng was developed by College of Agriculture, South China Agricultural University (SCAU), (Peiai64S × taifengzhan), which is a two-line hybrid rice. Its whole growth period is about 125 and 115 days for early and late planting, respectively. Huayou86 is new treatment combination of late maturity-temperate three-line hybrid rice. Whole growth period in Guangdong province is 130 days for early growing season and 115–120 days for late growing season, respectively. Subplot treatments included (1) the CK, (2) GA3 treatment, (3) PBZ treatment, and (4) 6-BA treatment. All plant growth regulators above were purchased from Xiamen Top using Chemical Co., Ltd (Fujian, P.R. China).
Twenty-day-old seedlings from wet bed nurseries were transplanted at the rate of 2 seedlings per hill at a spacing of 20.0 cm × 20.0 cm (2.5×105 hills ha-1) on 5th of April and 12th of August, respectively. Phosphorus in the form of single superphophate (SSP) was applied at the rate of 67.5 kg P2O5 ha-1 as basal dose. Potassium (potassium chloride) at 162 kg K2O ha-1 was applied with a split of 60% as basal dose and 40% at panicle initiation stage (PI). Nitrogen (urea) was applied with 50% as basal dose, 30% at mid-tillering (MT) and 20% at PI. The area of each sub-plot was 10 m2. The field was kept flooding from transplanting until 10 days before maturity when the field was drained. Disease and weeds were intensively controlled to avoid yield loss.
Foliar application of growth regulators
The solution of GA3 (20 mg L-1), PBZ (50 mg L-1), and 6-BA (30 mg L-1) was prepared, respectively. Foliar application of growth regulators was carried out at the heading stage by spraying plants uniformly to the point of run-off (approximately 100 mL m-2) using a Gloria type hand sprinkler (Guangzhou, P.R. China) with constant flow. Each plot was sprayed with 1.0 L of the specific solution. Control plot was treated with water. The treatments were applied late in the afternoon. The concentration of each substance was selected on the basis of previous experiments conducted since 2005 by our laboratory to establish optimum dosages for various rice cultivars, including the the two cultivars used in this study, and on actual practices employed by farmers in Guangzhou.
Plant samplings and enzymes activities measurement
Twenty flag (Top) leaves from each treatment were sampled at random and treated with liquid nitrogen for 1 min. Then they were stored at −80°C for enzymes activities measurements i.e. SOD, POD and MDA at 7, 14, 21 and 28 days after heading. The level of leaf senescence was determined by measuring the amount of MDA, which is the end product of lipid peroxidation, following the method of De Vos et al. (1991). Leaf samples (0.5 g) were homogenized in 5 mL of 5% trichloroacetic acid. The homogenate was centrifuged at 4 000× g for 10 min at 25°C and 3 mL of 2-thiobarbituric acid in 20% trichloroacetic acid was added to a 2 mL aliquot of the supernatant. The mixture was heated at 98°C for 10 min and cooled rapidly in an ice bath. After centrifugation at 4 000× g for 10 min, the absorbance was recorded at 532 nm. Measurements were corrected for non-specific turbidity by subtracting the absorbance at 600 nm. Concentration of MDA was determined by extinction coefficient MDA (ε= 155 μm cm-1).
SOD was measured according to the method described by Beauchamp and Fridovich (1971) using nitro blue tetrazolium (NBT). The assay mixture comprised of 1.5 mL of 0.1 mol L-1 phosphate buffer(PB, pH=7.5), 0.3 mL of 1.3 mol L-1 Methionine, 0.3 mol of 750 umol L-1 NBT, 0.3 mL of 100 umol L-1 EDTA-Na2, 0.3 mL of Riboflavin and 0.25 mL of distilled water. A total volume of 3.0 mL of assay mixture was reached by adding 0.05 mL of enzyme extract (0.05 mL of phosphate buffer saline (PBS) for the blank test). The assay mixture was exposed later uniformly under a light source of 4000×g for 20 min. Under these conditions riboflavin was excited by a photon and was able to oxidize an electron donor molecule in this case methionine. This donation of an electron results in the production of a superoxide molecule (O2-). The O2- molecule was able to reduce the NBT, giving an insoluble purple formazan. This colour change can be measured by spectrophotometer at A560 nm. The presence of SOD leads to a reduction in the level of formazan being produced. One unit of SOD was defined as the amount of enzyme necessary to produce a 50% inhibition of the maximum value of inhibition. It should be noted that even extremely concentrated forms of the enzyme never lead to a 100% inhibition, and so the 50% mark was defined as being the midpoint between no inhibition and the point where maximal (but not complete) inhibition takes place.
The peroxidase (POD) activity was determined using the method of Cai et al. (2008). Fresh leaf segments(<2 mm, 0.25 g) were homogenized in an ice bath in 5 mL of 50 mM borate buffer(pH 8.7) containing 5.0 mM sodium hydrogen sulfite and 0.1 g polyvinylpyrrolidone (PVP) The homogenate was centrifuged at 9000 g for 15 min at 4°C. The supernatant was used as enzyme extract. POD activity was assayed by adding 0.1 mL of the enzyme extract to a substrate mixture containing acetate buffer (0.1 mol L-1, pH 5.4), ortho-dianisidine (0.25% in ethyl alcohol) and 0.1 mL 0.8% H2O2 was added to 0.1 mL of the enzyme extract. Absorbance change of the brown guaiacol at 460 nm was recorded for calculating POD activity. One POD unit of enzyme activity was defined as the absorbance increase because of guaiacol oxidation by 1 unit min-1 (U g-1 FW min-1).
Harvesting and grain quality measurements
Yield and its components were determined according to the method described by Peng et al. (2006) with minor modification. At maturity, 30 hills of plants from each sub-plot were investigated for calculation of the average valid panicle numbers per hill. Then, six representative hills of the plants were separately sampled and investigated for yield components. Panicles were hand-threshed and ripened grains were separated from unripe grains by submerging them in tap water. Three subsamples of 30 g of ripened grains and 5 g of unripe grains were taken to count the number of spikelets. The ripened grains were then oven-dried at 70°C until constant weight for determining grain weight. Percentage of ripened grains (100 × ripened grains number/total grain number), and harvest index (100 × ripened grains weight /aboveground total biomass) were calculated. Grain yield was determined by harvesting an area of 5 m2 in the centre of each sub-plot (excluding the border lines) and adjusted to the standard moisture content of 0.14 g H2O g-1.
Grain quality measurements were determined according to the method described by Zhang et al. (2008). About 500 g of grains harvested from each subplot were dried at 40°C in a forced-air oven for quality analysis. A 150 g sample of rice grains were twice passed through a dehusker, polished, then separated into broken and unbroken grains. The brown rice rate, milled rice rate, and head rice rate were expressed as percentages of total (150 g) rice grains. Chalkiness was evaluated visually on 100 milled grains per subplot. Grains containing 20% or more white belly, white centre, and white back or a combination of these were considered chalky. Amylose content and protein content were measured according to Rice Quality Measurements Standards (Ministry of Agriculture, PR China, 1988).
Analyses of variances (ANOVA) were made with the General Linear Model Procedure of SAS statistical software version 8.1 (SAS Institute 2003). ANOVA was used to determine the treatment effects on each variable and confidence intervals derived from these analysis used to establish significant effects. Tukey’s test was used for comparison of significant effects.
Days after heading
Super oxide dismutase
The present research was financially supported by Agriculture Study Foundation of Guangdong Province (2004B20101007), Extended Demonstration Foundation of Production-Study-Research in Super Hybrid Rice of the Ministry of Agriculture of China (4100-F07063), Science Technology Foundation of Guangdong Province (2011AO20202001) and the Natural Science Foundation of Guangdong Province, China (S2011040004466). The authors are obliged to the anonymous reviewers and editors who we would also like to thank for their thoughts, comments and suggestions.
- Anjum SA, Wang LC, Farooq M, Hussain M, Xue LL, Zou CM: Brassinolide application improves the drought tolerance in maize through modulation of enzymatic antioxidants and leaf gas exchange. J Agron Crop Sci 2011, 197: 177–185. 10.1111/j.1439-037X.2010.00459.xView ArticleGoogle Scholar
- Bahram B: Amelioration of chilling stress by paclobutrazol in watermelon seedlings. Sci Hortic-Amsterdam 2009, 121: 144–148. 10.1016/j.scienta.2009.01.028View ArticleGoogle Scholar
- Beauchamp C, Fridovich I: Superoxide dis mutase: improved assays and an assay applicable to acrylamide gels. Anal Biochem 1971, 44: 276–287. 10.1016/0003-2697(71)90370-8View ArticlePubMedGoogle Scholar
- Cai KZ, Gao D, Luo SM, Zeng RS, Yang JY, Zhu XY: Physiological and cytological mechanisms of silicon-induced resistance in rice against blast disease. Phys Plasmas 2008, 134: 324–333.Google Scholar
- De Vos CH, Schat MD, Waal VR, Ernst W: Incrreased resistance to copper-induced damage of the root cell plasmalemma in copper tolerant Silena cucubalis. Plant Physiol 1991, 82: 523–528. 10.1111/j.1399-3054.1991.tb02942.xView ArticleGoogle Scholar
- Dong MH, Liu XB, Lu CQ, Zhao BH, Yang JC: Effects of exogenous ABA and GA on the main quality characteristics of grains at different positions of panicle in rice. Sci Agric Sin 2009,35(5):899–906. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Dong CF, Gu HR, Ding CL, Xu NX, Liu NQ, Qu H, Shen YX: Effects of gibberellic acid application after anthesis on the feeding value of double-purpose rice (Oryza sativa L.) straw at harvest. Field Crops Res 2012, 131: 75–80.View ArticleGoogle Scholar
- Du YX, Lu QL, Zhang J, Li JZ, Zhao QZ: Effects of exogenous hormones on grain plumpness and quality of rice. J Henan Agric Sci 2010, 12: 22–25. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Ekamber K, Kumar MP: Hormonal regulation of tiller dynamics in differentially-tillering rice cultivars. Plant Growth Regul 2007, 53: 215–223. 10.1007/s10725-007-9221-zView ArticleGoogle Scholar
- Emongor V: Gibberellic acid (GA3) influence on vegetative growth, nodulation and yield of cowpea (Vigna unguiculata L). J Agron Sci 2007, 6: 509–517.View ArticleGoogle Scholar
- Gapper NE, Coupe SA, McKenzie MJ, Sinclair BK, Lill RE, Jameson PE: Regulation of harvest-induced senescence in broccoli (Brassica oleracea var. italica) by cytokinin, ethylene, and sucrose. J Plant Growth Regul 2005, 24: 153–165. 10.1007/s00344-005-0028-8View ArticleGoogle Scholar
- Hall MA, Moshkov IE, Novikova GV, Mur LAJ, Smith AR: Ethylene signal perception and transduction: multiple paradigms? Biol Rev 2001, 76: 103–128.View ArticlePubMedGoogle Scholar
- Jiang ZR: Main popularized cultivars and techniques in agricultural area in Guangdong province in 2008. Guangdong Agric Sci 2008, 1: 63–64. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Lin KH, Pai FH, Wang SY, Lo HF: Pre-treating paclobutrazol enhanced chilling tolerance of sweet potato. Plant Growth Regul 2006, 49: 249–262. 10.1007/s10725-006-9135-1View ArticleGoogle Scholar
- Maclean JL, Dawe DC, Hardy B, Hettel GP: Rice Almanac(Third edition). IRRI, WARDA, CIAT and FAO: Philippines; 2002.Google Scholar
- Ministry of Agriculture, PR China: Standard of ministry of agriculture, PR China (NY83–88)-Methods for rice quality measurement. Chinese Standard Press, Beijing; 1988:4–6. (in Chinese) (in Chinese)Google Scholar
- Morinaka Y, Sakamoto , Yoshiaki I, Masakazu A, Hidemi K, Motoyuki A, Makoto M: Morphological alteration caused by Brassinosteroid insensitivity increases the biomass and grain production of rice. Plant Physiol 2006, 141: 924–931. 10.1104/pp.106.077081PubMed CentralView ArticlePubMedGoogle Scholar
- Olszewki SNT, Gubler F: Gibberellins signaling: biosynthesis, catabolism and response pathways. Plant Cell 2002, 14: S61–80.Google Scholar
- Peng S, Buresh RJ, Huang JL, Yang JC, Zou YB, Zhong XH, Wang GH, Zhang FS: Strategies for overcoming low agronomic nitrogen use efficiency in irrigated rice systems in China. Field Crop Res 2006, 96: 37–47. 10.1016/j.fcr.2005.05.004View ArticleGoogle Scholar
- Peng ZP, Huang JC, Yu JH, Yang SH, Li WY: Effects of PP333 and nutrient elements applied on yields and root growth of rice. Chin Agric Sci Bull 2011,27(05):234–237. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Pingali PL, Hossain M, Gerpacio RV: Asian Rice Market: Demand and Supply Prospects, Asian Rice Bowls: The Returning Crisis? CAB International, Wallingford, UK, and International Rice Research Institute, Los Baños, Philippines. 1997, 126–144.Google Scholar
- Rajendra B, Jones Jonathan DG: Role of plant hormones in plant defence responses. Plant Mol Biol 2009, 69: 473–488. 10.1007/s11103-008-9435-0View ArticleGoogle Scholar
- Richards DE, King KE, Ali AT, Harberd NP: How gibberellins regulates plant growth and development: a molecular genetic analysis of gibberellins signaling. Plant Mol Biol 2001, 52: 67–88.Google Scholar
- Sakamoto K, Komatsu T, Kobayashi T, Rose MT, Aso H, Hagino A, Obara Y: Growth hormone acts on the synthesis and secretion of alpha-casein in bovine mammary epithelial cells. J Dairy Res 2005, 72: 264–270. 10.1017/S0022029905000889View ArticlePubMedGoogle Scholar
- Sarkar PK, Haque MS, Karim MA: Effects of GA3 and IAA and their frequency of application on morphology, yield contributing characters and yield of soybean. J Agr Sci 2002, 1: 119–122.Google Scholar
- SAS Institute: SAS Version 9.1.2# 2002–2003. SAS Institute, Inc, Cary, NC; 2003.Google Scholar
- Still JR, Pill WG: Growth and stress tolerance of tomato seedlings (Lycopersicon esculentum Mill.) in response to seed treatment with paclobutrazol. J Hortic Sci Biotech 2004, l79: 197–203.Google Scholar
- Yan W, Zhang XX, Yuan A: Effects of two plant growth regulators on the growth and recovery of alfalfa seedlings exposed to Aluminum stress. J Shanghai Jiaotong Univ (Agric Sci) 2011,29(2):75–82. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Yang JC, Peng SB, Visperas Romeo M, Sanico Arnel L, Zhu QS, Gu SL: Grain filling pattern and cytokinin content in the grains and roots of rice plants. Plant Growth Regul 2000, 30: 261–270. 10.1023/A:1006356125418View ArticleGoogle Scholar
- Yuan GF: Development of hybrid rice and its prospect. Chin Agric Sci Bull 2011,27(15):6–11. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Yuan Y, Qian HM, Wang Y, Shi YM, Tang DQ: Hormonal regulation of Freesia cutflowers and FhACS1. Sci Hortic-Amsterdam 2012, 143: 75–81.View ArticleGoogle Scholar
- Zhang WX, Peng CR, Sun G, Zhang FQ, Hu SX: Effect of different external phytohormones on leaves senescence in late growth period of late-season rice. Acta Agric Jiangxi 2007,19(2):11–13. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Zhang ZC, Zhang SF, Yang JC, Zhang JH: Yield, grain quality and water use efficiency of rice under non-flooded mulching cultivation. Field Crop Res 2008, 108: 71–81. 10.1016/j.fcr.2008.03.004View ArticleGoogle Scholar
- Zheng LY, Wu WG, Yan C, Zhang YH, Xu YZ, Xu RM, Wang HY, Cui N, Chen ZQ: Effects of plant growth regulators on photosynthetic rate and yield components of rice. Crops 2011, 3: 63–66. (in Chinese with English abstract) (in Chinese with English abstract)Google Scholar
- Zvi P, Eduardo B: Hormone balance and abiotic stress tolerance in crop plants. Curr Opin Plant Biol 2011, 14: 290–295. 10.1016/j.pbi.2011.02.001View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.