Effects of Bicarbonate and High ph Conditions on Zinc and Other Nutrients Absorption in Rice

Transcription

1 290 Rice Science, 2004, 11(56): Effects of Bicarbonate and High ph Conditions on Zinc and Other Nutrients Absorption in Rice MENG Fanhua, WEI Youzhang, YANG Xiaoe, LIN Jianjun, LIU Jianxiang (College of Environmental and Resource Sciences, Zhejiang Universtiy, Hangzhou ) Abstract: Zinc deficiency was widely observed in calcareous soil where bicarbonate and high ph were always related with low zinc availability. In a hydroponic experiment, one zincefficient rice (IR36) and one zincinefficient rice (IR26) genotypes were employed to investigate the effects of bicarbonate and high ph conditions on absorption, transport of zinc and other nutrients (P, K, Ca, Mg, Fe, Cu, Mn) in rice. As compared with the control, high ph inhibited absorption, translocation and accumulation of zinc and other nutrients in both rice genotypes. Bicarbonate had minor effect on zincefficient rice genotype (IR36) whereas it could decrease zinc and other nutrient absorption in zincinefficient rice genotype (IR26). These results implied that increasing rice tolerance to bicarbonate is one of the most important strategies to improve rice adaptation for zincdeficit calcareous soil. Key words: rice; zinc efficiency; ph; bicarbonate; nutrient absorption Soil zinc deficiency is prevalent in the world. It is estimated that more than 40% of the soils surveyed in 19 countries [1], and more than 40% of the total land area in China are zinc deficient. The severe zinc deficiency had been observed in the calcareous soil [2]. High concentration HCO 3 had been considered to play an important role in zinc deficiency mechanism in calcareous soil [36]. Large genotypic differences in Znefficiency in rice have been identified [4, 5]. The previous experiments indicated that 5 to 10 mmol/l HCO 3 was not only harmless, but also enhanced the growth of Znefficient rice genotype (IR36), increasing the absorption and transport of zinc. Presently, the research about the effects of bicarbonate and high ph on zinc and other nutrients absorption of rice differing in zinc efficiency is rare. In this paper, the absorption and accumulation of Zn, P, K and other nutrition elements responding to bicarbonate and high ph in Zn efficient rice IR36 and Zn inefficient rice IR26 were investigated in order to further unravel the physiological mechanism of zinc efficiency difference in different rice genotypes. MATERIALS AND METHODS Plant growth and treatment One zincefficient (IR36) and one zincinefficient Received: 11 June 2004; Accepted: 15 September 2004 Corresponding author: WEI Youzhang (IR26) rice genotypes were selected for this study, which were kindly provided by the International Rice Research Institute. Rice seedlings were grown in nutrient solution with the following composition [7] : NH 4 NO mmol/l, CaCl mmol/l, MgSO mmol/l, KH 2 PO mmol/l, K 2 SO mmol/l; MnSO µmol/l, H 3 BO µmol/l, CuSO µmol/l, (NH 4 ) 6 Mo 7 O µmol/l. Iron was supplied as FeEDDHA with EDDHA (ethylene bis[2(ohydroxyphenyl)glycine]) at 0.01 mmol/l and 0.1 mmol/l during preculture and treatment, respectively. Nutrient solution was replaced every three days interval. Three treatments included control (ph 6.0); high ph level (), buffered with N2 hydroxyethylpiperazinn2ethansulfonate (HEPES); Bicarbonate, supplied as NaHCO 3 at 10 mmol/l. There were three replicates for each treatment. Rice seeds were germinated in the dark on filter paper, transferred onto a nylon net and precultured in distilled water containing 0.02 mmol/l CaSO 4 for 5 days. Then the selected rice seedlings with similar size were transplanted into 3.0 L plastic pots. Every pot had 7 clusters with 6 plants each. These rice seedlings were precultured in 0.25 and 0.50fold nutrition solution for 2 and 5 days sequentially. Solution ph of control was adjusted to 6.0 using 0.1 mmol/l NaOH or 0.1 mmol/l HCl, whereas solution

2 MENG Fanhua et al. Effects of Bicarbonate and High ph on Zinc and Other Nutrients Absorption of Rice 291 ph of the high ph treatment was maintained at 8.0. The nutrition solutions were replaced every 3 days interval. Measurements Six plants were randomly sampled from each pot for zinc determination at 2, 4, 6 and 8 days after posttreatments. The other elements (P, K, Ca, Mg, Fe, Cu, Mn) were determined at 8 days after posttreatments. The shoot and root parts of these rice plants were dried by heat separately. The dried plant materials were weighed and finely ground (60 mesh). Later, they were ashed in muffle furnace for 6 h at 550, dissolved in 1:3 HCl and analyzed with Atomic Absorption Spectrophotometry [8] for the Zn, P, K, Ca, Mg, Fe, Cu, and Mn contents. RESULTS Effect of bicarbonate and high ph conditions on dry weight of the Zninefficient and Znefficient rice cultivars Table 1 revealed that, the growth of both shoot and root in the Znefficient rice genotype (IR36) was enhanced by, especially the root part. For instance, the shoot and root biomasses were 0.75% and 7.79%, 4.95% and 8.10%, 7.38% and 14.69% higher in Znefficient rice genotype (IR36) than those in the control at 4, 6, 8 days after treatments, respectively. The fast growth of root was Table 1. Effect of bicarbonate and high ph on dry weight of the Zninefficient and Znefficient rice cultivars. mg/plant for 2 days for 4 days Shoot Root Root/Shoot Shoot Root Root/Shoot IR36(Znefficient) bcab aa a 0.38 aa bb bb 0.46 bb cb aa 0.41 aa cc cb 0.48 aab (92.31) (89.12) (93.88) bcab aa 0.37 aa bb aa 0.49 aa (99.72) (100.03) (100.75) (107.79) IR26(Zninefficient) aa aa 0.38 aa aa aa 0.42 cc abab aa 0.39 aa bb bb 0.42 cc (93.76) (95.89) (89.59) (89.19) abab aa 0.40 aa bb bb 0.42 cc (92.86) (95.65) (88.27) (87.96) for 6 days for 8 days Shoot Root Root/Shoot Shoot Root Root/Shoot IR36(Znefficient) bb bb 0.53 abab ba cb 0.54 cbc dd (83.61) cc (87.31) 0.56 aa db (78.93) dc (91.22) 0.63 aa abab (104.95) aa (108.10) 0.55 aab aa (107.38) aa (114.69) 0.58 bb IR26(Zninefficient) aa bb 0.48 cb aa bb 0.53 cc cc (84.62) cc (87.52) 0.49 bcab cb (80.50) ed (81.77) 0.54 cbc ccd (81.52) cc (86.91) 0.51 abcab db (75.48) 23.21eD (79.14) 0.55 bcbc a Data in the parentheses represent the percentage of the treatment to CK. Data followed by the same uppercase and lowercase letters within a column indicate no significant difference at 1% and 5% levels in a genotype, respectively.

3 292 Rice Science, Vol. 11, No. 56, 2004 propitious to the absorption of nutrients and water to maintain the plant growth. The root and shoot growth, especially the shoot, in Zninefficient rice genotype (IR26) was inhibited by. Similarly, the growth of the root and shoot in both rice genotypes was decreased by high ph, and the shoot was more sensitive than the root. Bicarbonate and high ph regime could affect the root to shoot ratio (Table 1). As a response of rice against the stress, the ratio of root to shoot of both rice genotypes increased with the prolongation of treatment time. Briefly, Zn deficiency inhibited the growth of rice shoot and root, but the effect on root was less apparent than that on shoot relatively, which ensured the basic nutrition for rice growth. The studies displayed that in both rice genotypes, the ratios of root to shoot were increased by 10 mmol/l HCO 3 and high ph with different degree. As to Znefficient rice genotype (IR36), the increase ratio of root to shoot by high ph was larger than that by 10 mmol/l HCO 3, indicating that could enhance the even growth of roots and shoots in the Znefficient rice (IR36). As a response to high ph,znefficient rice genotype (IR36) displayed the significant resistance to the stress. In opposition, in Zninefficient rice genotype (IR26), the ratio of root to shoot was larger under treatment, than under high ph, indicating that high concentration HCO 3 could display a more inhibition on the growth of the Zninefficient rice genotype than high ph in calcareous soil. Effect of bicarbonate and high ph on the zinc absorption and accumulation in rice Effect of bicarbonate and high ph on the zinc content in root and shoot of Zninefficient and Znefficient rice genotypes As shown in Table 2, Zn content in the roots of both rice genotypes, IR26 and IR36, was decreased gradually with the increase of treatment time. According to ANOVA, as compared with the control, had no significant effect on the root Zn content in the Znefficient rice genotype (IR36), but had a significant impact on Zninefficient rice genotypes (IR26) at 6, 8 days after treatment. There was no significant difference in root Zn content of both rice genotypes by the treatment of. Contrasted with the control under treatment, no pronounced difference was observed for shoot Zn concentration in Znefficient rice genotypes (IR36), but shoot Zn content in Zninefficient rice genotypes (IR26) was significantly or wondrously significantly reduced. After treatment for 2, 4, 6, 8 days, Zn contents of the shoot were decreased by 2.97%, 8.12%, 12.63% and 20.37%, respectively. After treatment for 2 to 8 days, shoot Zn concentrations of both rice genotypes were dramatically reduced (4.13% to 23.70% and 2.97% to 20.37%) under high ph (8.0), respectively. Effect of bicarbonate and high ph on the ratio of zinc content of shoot to root in the Zninefficient and Znefficient rice genotypes The effect of was variable on Table 2. Effect of bicarbonate and high ph on the zinc content (mg/kg) in root and shoot of Zninefficient and Znefficient rice genotypes. 2 days after treatment 4 days after treatment 6 days after treatment 8 days after treatment Shoot Root Shoot Root Shoot Root Shoot Root IR36 (Znefficient) aa aa aa aa aa aa aa aa aa ba bb aa bb aa bb bb aa aa aa aa aa aa aa aa IR26 (Zninefficient) aa aa aa aa aa aa aa aa aa ba ba aa bb ba bb bb aa ba aba aa bb ba bb bb Data followed by the same uppercase and lowercase letters within a column indicate no significant difference at 1% and 5% levels in a genotype, respectively.

4 MENG Fanhua et al. Effects of Bicarbonate and High ph on Zinc and Other Nutrients Absorption of Rice 293 Table 3. Effect of bicarbonate and high ph on the ratio of zinc content in shoot to root of the Zninefficient and Znefficient genotypes. Ratio of Zn content in shoot and root 2 days after 4 days after 6 days after 8 days after IR36(Znefficient) IR26(Zninefficient) 0.51 a 0.58 aba 0.66 aa 0.67 aa 0.50(98.49) 0.54 ba(91.61) 0.57 bb(85.99) 0.56 bb(83.69) 0.51(99.98) 0.61 aa(104.74) 0.66 aa(100.88) 0.71 aa(104.77) aa 0.60 aa 0.66 aa 0.53(101.71) 0.52 aa(92.94) 0.55 bb(91.49) 0.56 bb(84.17) 0.53(101.87) 0.53 aa(94.75) 0.55 bb(92.11) 0.57 bb(85.71) a Data in the parentheses represent the percentage of the treatment to CK. Data followed by the same uppercase and lowercase letters within a column indicate no significant difference at 1% and 5% levels in a genotype, respectively. Zn availability in rice genotypes (Table 3). As for an example 10 mmol/l HCO 3 enhanced the ratio of zinc content of shoot to root in the Znefficient rice genotype (IR36), and the effect was increased with the prolongation of treatment time. In contrast, the ratio of zinc content of shoot to root in the Zninefficient rice genotype (IR26) was decreased by 10 mmol/l HCO 3. The decreasing degree was significantly depended upon the increased duration of the treatment time. This revealed that under Zndeficiency stress, possibly enhanced Zn absorption in Znefficient rice genotype (IR36) roots. However, the transportation of Zn from root to shoot was inhibited by 10 mmol/l HCO 3, inducing the Zn deficient symptom in shoots. As a rule, rice genotypes had the similar reaction to high ph, i.e. the ratio of zinc content of shoot to root reduced gradually with the prolonged treatment time. On the contrary, the decreasing degree of the Znefficient rice genotype (IR36) was larger than that of the Zninefficient rice genotype (IR26). In brief, under high concentration HCO 3 (10 mmol/l) stress, Znefficient rice genotype (IR36) may be stimulated the zinc transportation to shoot to resist zinc deficient stress. Effect of bicarbonate and high ph (8.0) on the absorption and accumulation of other nutritive elements Absorption and accumulation of P Compared with the control, P absorption and accumulation in root and shoot of both two rice genotypes were significantly reduced by high ph (8.0) treatment, the inhibition to the absorption and accumulation in root was more significant than that of shoot (Fig. 1, Table 4). Under stress, P absorption and accumulation in root and shoot of Znefficiency rice genotype (IR36) increased, on the contrary, that in root of Zninefficient rice genotype (IR26) decreased. But compared with the control, P absorption and accumulation of shoot both were enhanced, respectively. Absorption and accumulation of K HCO 3 (10 mmol/l) enhanced K absorption of Znefficient rice genotype (IR36), and increased the K accumulation in plant. In contrast, the same concentration of HCO 3 inhibited K absorption and transportation in Zninefficient rice genotype (IR26), resulting in reduction of K content and accumulation in plant. Under high ph stress, K absorption and accumulation in both two rice genotypes were inhibited, and significantly lower than those of the control (Table 4, Fig. 1). Absorption and accumulation of Ca, Mg, Fe, Cu and Mn HCO 3 (10 mmol/l) promoted Ca absorption and accumulation in Znefficient rice genotype (IR36), whereas dramatically restrained that in Zninefficient rice genotype (IR26), especially in root. Compared with the control, Ca accumulation in root and shoot of Znefficient rice genotype (IR36) was increased by 28.34% and 11.39% respectively, while Ca

5 294 Rice Science, Vol. 11, No. 56, 2004 Table 4. Effect of bicarbonate and high ph on the P, K, Ca, Mg, Cu, Mn, Fe content of plant of the Zninefficient and Znefficient rice cultivars. P (mg/kg) K (mg/kg) Ca (mg/kg) Shoot Root Shoot Root Shoot Root Znefficient IR36 Zninefficient IR26 CK (ph 6.0) CK (ph 6.0) Cu (mg/kg) Mn (mg/kg) Fe (mg/kg) Mg (mg/kg) Shoot Root Shoot Root Shoot Root Shoot Root Znefficient IR36 Zninefficient IR26 CK (ph 6.0) CK (ph 6.0) accumulation in root and shoot of Zninefficient rice genotype (IR26) was significantly decreased by 71.38% and 45.74%, respectively. High ph regime reduced significantly both Ca absorption and accumulation in the two rice genotypes (Fig. 1, Table 4). The effect on Mg content and accumulation in two rice genotypes was the same to that of Ca under different treatments, such as Fig. 1. Effect of bicarbonate and high ph on the P, K, Ca, Mg, Cu, Mn and Fe accumulation in plant of the Zninefficient and Znefficient rice cultivars. On the abscissa, number 1, 2, 3, and 4 represent shoot of IR36, shoot of IR26, root of IR36, and root of IR26, respectively.

6 MENG Fanhua et al. Effects of Bicarbonate and High ph on Zinc and Other Nutrients Absorption of Rice 295 enhanced Mg absorption and accumulation in Znefficient rice genotype (IR36); but decreased that in Zninefficient rice genotype (IR26), the reducing extent was larger in root than in shoot. High ph inhibited Mg absorption and accumulation in two rice genotypes (Fig. 1, Table 4). HCO 3 (10 mmol/l) stimulated Znefficient rice genotype (IR36) to absorb Fe, Cu, Mn, and increased Fe, Cu, Mn content in plants, especially in shoots. On the contrary, 10 mmol/l HCO 3 restrained the Fe, Cu and Mn absorption and transportation in Zninefficient rice genotype (IR26), reduced the content of shoot and root. Compared with the control, high ph reduced Fe, Cu and Mn absorption and accumulation in two rice genotypes (Fig. 1, Table 4). DISCUSSION Zinc deficiency of rice was observed mainly in calcareous soil where bicarbonate and high ph conditions were associated with low zinc availability [2]. Znefficient rice genotype (IR36) was more tolerant to zincdeficiency than Zninefficient rice genotype (IR26) under bicarbonate stress as disclosed in previous results [6, 7]. In this paper, the results revealed that there did not exist genotypic difference in Zn absorption between two Zn efficiency rice cultivars under stress, but the effect on the two rice genotypes by was significantly variable. Znefficient rice genotype (IR36) was more tolerant to Zn deficiency, in which the normal Zn absorption and transportation could be maintained. The ability of Zn absorption in Zninefficient rice genotype (IR26) was significantly inhibited, causing serious Zndeficient symptoms on shoots. Under high HCO 3 concentration stress, the root morphological characters of Znefficient rice genotype changed greatly, such as the increase of root surface area, root tip number, root length and others, enhancing Zn absorption and utilization. On the contrary, the root growth and elongation of Zninefficient rice genotype were significantly inhibited, which destroyed normal Zn absorption and transportation in rice roots, resulting in Zn deficient symptoms [9]. Being consistent with the previous studies, in shoot of Zninefficient rice genotype (IR26), P accumulation was increased, but the availability of other elements was decreased [1012], the reason for it was still unknown. Welch et al [10] ascertained that root cell would lose the ability to adjust P and Zn transportation to shoot under Zn deficient stress, because Zn is one of the composing ingredients of root cytoplasm membrane. In case of Zn deficiency, cytoplasm membrane will lose integrality, increase penetrability, therefore P transportation from root to shoot will be affected. Some experiments also proved that root cytoplasm membrane penetrability was increased by Zn deficiency stress, resulting in the nutrient loss and the increased nonselectivity absorption, and leading to the cytoplasm membrane peroxidation. Cakmak et al [11, 12] considered the process by which the plants with Zn deficiency accumulated high P in the shoot was not simple, in fact. Their experiments on the cotton showed that it could be related to the damage of the transport mechanism for P from shoot to root. Marscher et al [13] revealed that no P accumulated in the root of the rice plants under the condition of Zn deficiency, however, the P content was high in the shoot. Higher P/Zn in the shoot could affect the normal P, Zn metabolism, finally lead to the declined biomass of the shoot. During the process of plant growth, nutrition balance is required. Lack or excess of a certain nutrients will affect the nutrients uptake and disturb the balance in plant, and later interfere with plant physiological and biochemical process, which will cause the disordered metabolism and, therefore, reduce the quantity and quality of crops. This study demonstrated that under treatment, the Zninefficient genotype rice not only was lack of Zn, but also restrained the uptake and transport of other nutrition element such as potassium, calcium, magnesium, iron, copper and manganese, leading to the disordered metabolism, and the stagnant plant growth. ACKNOWLEDGEMENT This study was financially supported by the Outstanding Young Scientist Grant ( ) from the National Natural Science Foundation of China.

7 296 Rice Science, Vol. 11, No. 56, 2004 REFERENCES 1 Graham R D, Asher J S, Hynes S C. Selecting zincefficient cereal genotypes for soil of low zinc status. Plant Soil, 1992, 146: Liu Z. Regulations of content and distribution of zinc in soils of China. Acta Agric Sin, 1994, 27(1): (in Chinese with English abstract) 3 Forno D A, Youshida S, Asher C J. Zinc deficiency in rice. I. Soil factors associated the deficiency. Plant Soil, 1975, 42: Youshida S, Tanaka A. Zinc deficiency of the rice plant in calcareous soils. Soil Sci Plant Nutr, 1969, 15: Yang X, Römheld V, Marschner H. Effect of bicarbonate and root zone temperature on the uptake of Zn, Fe, Mn and Cu by different rice cultivars (Oryza sativa L.) grown in calcareous soil. Plant Soil, 1993, 155/156: Yang X E, Römheld V, Marschner H. Micronutrient uptake by hybrid and conventional rice cultivars from different types of soils. J Plant Nutr, 1994, 17: Yang X E, Römheld V, Marschner H, Chaney R L. Application of chelatorbuffered nutrient solution technique in studies on zinc nutrition in rice plant (Oryza sativa L.), Plant Soil, 1994, 163: Nanjing Agricultural University. Soil and Agricultural Chemistry Analysis. Beijing: Chinese Agricultural University Publisher, Hajiboland R, Yang X E, Römheld V. Effects of bicarbonate and high ph on growth of Znefficient and Zninefficient genotypes of rice, wheat and rye. Plant Soil, 2003, 250: Welch R M, Webb M I, Loneragan J F. Zinc in membrane function and its role in phosphorus toxicity. In: Scaife A. Plant Nutrition. Proceedings of the 9th International Plant Nutriton Colloquium. Slough, UK: Warwich University, Cakmak I, Marschner H. Mechanism of phosphorus induce zinc deficiency in cotton. Physiol Plant, 1987, 70: Cakmak I, Marschner H. Enhance superoxide radical production in root of zincefficient plants. J Exp Bot, 1988, 39: Marschner H. Zinc uptake from soils. In: Robson A D. Zinc in Soils and Plant. Dordrecht: Kluwer Academic Publishers,