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Effects of different cropping patterns on the physiology and quality of Pseudostellariae heterophylla.

Byline: Sheng Lin Jingjing Huangpu Ting Chen Linkun Wu Zhongyi Zhang and Wenxiong Lin

Abstract

Pseudostellariae heterophylla has the problem of continuous cropping obstacle resulting in significant reductions in yield and quality. In this study different cropping patterns were designed to investigate the effects on the physiology yield and medicinal quality of P. heterophylla. Continuous cropping resulted in significant decline in the production and quality the output and pharmacological components of two-year monoculture than of one-year monoculture of P. heterophylla. Compared with two-year monoculture the rice -P. heterophylla and bean -P. heterophylla rotation increased the production and pharmacological components of P. heterophylla. These rotation patterns improved the photosynthetic capacity of P. heterophylla and reduced the activity of protective enzymes and malondialdehyde content of P. heterophylla. The results indicated that rotation cropping can alleviate continuous cropping obstacles and improve the yield and quality of P. heterophylla. The rice- P. heterophylla rotation is more effective than bean- P. heterophylla to abate the continuous cropping obstacles of P. heterophylla. Copyright 2014 Friends Science Publishers

Keywords: Pseudostellaria heterophylla; Continuous cropping obstacles; Rice -P. heterophylla rotation; Bean -P. heterophylla rotation; Physiology.

Introduction

The Pseudstellariae heterophylla belongs to family Caryophyllaceae and is used as common and highly demanded traditional Chinese medicine. It is mainly planted in Fujian Guizhou Shandong Jiangsu and Anhui provinces and source of major economic income to local farmers. However like other medicinal plants such as Rehmannia glutinosa Panax ginseng Radix notoginseng and Coptis chinensis Angelica sinensis P. heterophylla suffers from continuous cropping obstacles (Lin et al. 2005; 2012; Zeng et al. 2012). Most of medicinal plants with their roots used as medicine have more serious problem of continuous cropping obstacle than plants with their tissues used as medicines (Zhao 2000). For example the continuous cropping of Salvia miltiorrhiza resulted in exterior deformation of root decreased tuberous products and low content of active ingredient (Zhang et al. 2005).

And the field was used to plant some medicinal plants where same medicinal plants cannot be grown in next couple of years or for a long time. This phenomenon exists in the cultivation of R. glutinosa P. ginseng and Codonopsis pilosula. Two-year monoculture R. glutinosa had small plants imbalanced root- shoot ratio and shortened growth period. The tuberous roots of R. glutinosa were unable to develop into enlarged and commercial product form (Zhang et al. 2010; Wu et al. 2011; Li et al. 2012a). The emergence rate of ginseng fell below 30% in the field with two-year monoculture and the periderm of most roots were lousy red and full of disease scar (Jian et al. 2008). The problem is also very serious in the P. heterophylla continuous cropping which showed weak plant growth aggravating diseases decreased yield and poor quality (Zeng et al. 2012).

Due to the limited farmland planting conditions and economic incentive factors continuous cropping area of medicinal plants is growing in recent years (Zhang et al. 2011). And the problem of continuous cropping obstacle is becoming more serious. Therefore to solve continuous cropping obstacle of medicinal plant is a critical issue. To curb the continuous cropping obstacle some methods are used such as soil disinfection application of chemical and organic fertilizer adding biological agents or activated carbon breeding disease-resistant varieties and improving cultivation system (Wei et al. 2009). However there is need of effective method to decrease continuous cropping obstacle.

This study designed rice -P. heterophylla and bean -P. heterophylla rotation cropping modes in the GAP (Good Agriculture Practice) experimental field and analyzed physiological indexes yield and quality of P. heterophylla under different cropping patterns. The results aimed to explore the effect of different rotation cropping modes on abatement of P. heterophylla continuous cropping obstacle and might provide a theoretical reference for resolving the problems associated with P. heterophylla continuous monoculture.

Materials and Methods

Experimental Conditions and Crop Husbandry

The experiment was conducted in the GAP (Good Agriculture Practice) experimental field of P. heterophylla Zherong County Ninde Municipality Fujian Province P.R. China in 2009-2011. The P. heterophylla cultivarZheseng-2' was used for this study planted in December and harvested in July every year. The field trial with three replications consisted of five treatments including one-year monoculture (NP) two-year consecutive monoculture (CM) rice -P. heterophylla rotation (RP) bean -P. heterophylla rotation (BP) and fallow treatment (CK kept uncultivated). The experimental plot was 5 A- 5 m (25 m2) in each treatment. Individual P. heterophylla root was planted in plots at 5 A- 10 cm among plants. One-year monoculture was made on December 23 2010. The planting of two-yearconsecutive monoculture rice -P. heterophylla and bean -P.heterophylla rotation was made on December 23 2009 and2010. The rice and bean were respectively planted in July2010 and harvested in November 2010. The P. heterophylla completely germinated in March 2011 and were harvested in July 2011. The soil properties are shown in Table 1.

Determination of Different Component in P. heterophyllaRoot

Root moisture contents total ash acid insoluble ash content water soluble extract and alcohol soluble extract content of P. heterophylla were determined.

Determination of Leaf Photosynthesis Indexes andChlorophyll Content of P. heterophylla

In May 2011 of P. heterophylla growth peak period three plants of P. heterophylla were selected for photosynthesis indexes measurement. The chlorophyll content was measured by SPAD-502 chlorophyll meter. The LI-6400 photosynthetic apparatus was used to measure net photosynthetic rate (Pn) intercellular CO2 concentration (Ci) and stoma conductance (gs). Three plants of P. heterophylla were used to determine the biomass and physiological indicators.

Antioxidants Enzyme Activity and MalondialdehydeContent Assays

The 0.5 g of P. heterophylla leaf was weighed and grinded into homogenate using 2 mL phosphate buffer (50 mMphosphate pH 7.0 1% w/v PVP). The homogenate was moved into 10 mL centrifuge tube and centrifuged at 1000 g for 10 min. The supernatant was used to detect superoxide dismutase (SOD) peroxidase (POD) catalase (CAT) activity malondialdehyde (MAD) and protein content. The methods were referred to the book of plant physiology experiment (Wang 2006).

Polysaccharide and Saponin Content in P. heterophyllaRoot

The polysaccharide and saponin content were determined. The 100 mg glucose was dissolved by distilled water and diluted to 100 mL volume. Glucose solution was used to make standard curve. The 10 20 40 60 and 80 L glucose solution was removed into 15-mL tube and respectively added distilled water to 2 mL volume. Each concentration of glucose solution had three replications. The 2.0 mL of distilled water was used as blank control. In every tube 1.0 mL of phenol and 5 mL of concentrated sulfuric acid were added and kept for 5 min. After incubation in boiling water for 15 min the tubes were removed and cooled to room temperature. The optical absorption of the mixture was obtained at 490 nm. The standard curve was made by using glucose concentration levels as abscissa and absorbance as ordinate and linear regression equation was y = 0.0081 x - 0.0039 R = 0.9999.

The saponin content in P. heterophylla root wasdetermined by using Agilent HPLC system (Agilent HPLC system USA). The chromatographic system consisting of Agilent 1260 HPLC system with a reversed-phase column Zorbax Extend-C18 (150 mmA-4.6 mm 5 m column) was used at a flow rate of 1.0 mL min-1. The solvent system was solvent A (30% acetonitrile) and solvent B (70% water). The injected volume was 10 L. The UV detector was performed at 203 nm. The chromatographic data were recorded and processed with Agilent empower workstation. The standard of ginseng saponin Rb1 was dissolved in methanol and diluted into 0.1 0.2 0.3 0.4 0.5 and 1.0 mg mL-1. The standard curve was made by using saponin concentration levels as abscissa and area as ordinate and linear regression equation was y=0.0026x+0.0318 R2=0.9999.The polysaccharide and saponin content were extracted from P. heterophylla root and determined as described by Zeng et al. (2012).

Results

Photosynthetic Indexes and Biomass of P. heterophylla

The discretion of photosynthetic rate showed the ability of plant to produce assimilates. Different photosynthetic indexes can directly reflect the strength of photosynthesis. The increase of chlorophyll contents in leaves of newly planted P. heterophylla was 137% and photosynthetic rate was 200% of one year monoculture (Table 2).

Table 1: Soil physicochemical properties of experimental area

Treatments###Organic matter###Total N###Total P###Total K###Available N###Available K###Available P###pH

###(g kg-1)###(g kg-1)###(g kg-1)###(g kg-1)###(mg 100 g-1)###(mg kg-1)###(mg kg-1)

Fallow###38.31###5.01###0.47###19.77###19.78###21.07###185.89###5.7

One-year monoculture###38.88###2.02###0.47###20###18.2###30.09###174.52###5.18

Two-year consecutive monoculture###30.53###4.48###0.60###24.31###20.3###61.23###197.27###5.49

Rice -P. heterophylla rotation###26.74###1.90###0.54###19.55###23.8###38.42###242.79###5.24

Bean -P. heterophylla rotation###33.38###1.68###0.76###23.85###15.4###54.94###211.18###5.59

Table 2: Effects of different cropping patterns on the photosynthetic parameters biomass and yield of P. heterophylla

Treatment###Chlorophyll Net photosynthesis###Stomatal###Ci###Transpiration rate###Biomass###Yield

###(mg g-1 FW-1) (mol CO2 m-2 s-1)###conductance###(mol m-2 s-1)###(mol CO2 m-2 s-1)###(g plant-1)###(kg ha-1)

###(mol H2O2 m-2 s-1)

One-year monoculture###44.835.8a###8.6982.79a###0.240.016a###2830.58a###3.910.21a###4.010.6298a###7103.55241.50a

Two-year consecutive monoculture###32.746.3b###4.24131.79d###0.110.005c###2570.93b###2.120.06c###3.031.1489c###4082.10193.50bc

Rice -P. heterophylla rotation###47.114.9a###8.0221.82b###0.190.016b###2810.73a###3.690.15b###3.711.2984b###6555.90271.20ab

Bean -P. heterophylla rotation###44.914a###6.46871.85c###0.120.019c###2590.48b###2.340.14c###3.121.1212c###4602.15198.00b

Stoma conductance intercellular CO2 concentration and transpiration rate of newly planted P. heterophylla were higher than of one year monoculture. This indicates that monoculture reduces photosynthesis and restrains growth of P. heterophylla (Table 2). The chlorophyll content and photosynthetic rate of RP rotation was respectively 140% and 200% of one year monoculture P. heterophylla and other photosynthesis indexes of RP rotation were also higher than of one year monoculture. The effect of rice -P. heterophylla rotation to improve photosynthesis was more significant than of bean - P. heterophylla rotation. The increase of chlorophyll content and enhance of photosynthesis indexes were beneficial to plant growth and biomass accumulation. Compared with the biomass of one year monoculture P. heterophylla the increase of biomass in rice -P. heterophylla reached significant level (Table 2).

Antioxidants Enzymes Activity and MalondialdehydeContent

The consecutive monoculture increased the activity of protective enzyme and content of MAD. The activity of SOD in leaves of two-year consecutive monoculture was significantly higher than of one-year monoculture and reached 272% of one-year monoculture (Table 3). Activity of POD and CAT of two-year consecutive monoculture was also significantly higher than of one-year monoculture. The MAD content of two-year consecutive monoculture was130% of one-year monoculture (Table 3).Compared with protective enzymes activity and MAD content of two-year consecutive monoculture SOD POD and CAT activity in leaves of P. heterophylla significantly decreased under different rotation patterns. The SOD POD and CAT activity of rice -P. heterophylla rotation were respectively 54.81 90 and 65.48% of two-year consecutive monoculture (Table 3). And SOD POD and CAT activity of bean -P. heterophylla rotation were respectively 83.6596.33 and 86.28% of two-year consecutive monoculture (Table 3). It indicates that rotation can effectively alleviate the effects of superoxide anion free radical caused by P. heterophylla consecutive monoculture.

Yield of P. heterophylla under Different CroppingPatterns

There was significant difference of P. heterophylla yield between different cropping patterns (Table 2). The P. heterophylla yield of two-year consecutive monoculture was the lowest and 57.46% of one-year monoculture indicates that consecutive monoculture resulted in sharp decline of P. heterophylla yield. The P. heterophylla yield of rice -P. heterophylla rotation was 92.29% slightly lower than of one-year monoculture. The yield of P. heterophylla roots in bean -P. heterophylla rotation was 64.79% of one-year monoculture and lower than of rice -P. heterophylla rotation. It showed that compared with bean -P. heterophylla rotation rice -P. heterophylla rotation was more effective to increase the yield of P. heterophylla after consecutive monoculture.

Quality of P. heterophylla under Different CroppingPatterns

For the quality of P. heterophylla the national pharmacopoeia stipulated that water content is not more than 14% aqueous extract not less than 25% ethanol- soluble extract not less than 6% and ash content not more than 4% of dry weight (Table 4). The quality of different samples is according to the stipulation of national pharmacopoeia. The main medicinal components of P. heterophylla were polysaccharides and saponin (Fig. 1). The polysaccharides and saponin of two-year consecutive monoculture were significantly lower than of one-year monoculture respectively 81.5% and 73.3% of one-year monoculture. In rice -P. heterophylla rotation polysaccharides and saponin were respectively 116% and

Table 3: Antioxidants activities and MDA content in leaves of P. heterophylla

Treatments###SOD (U min-1 g-1)###POD (U min-1 g-1)###CAT (H2O2 mg g-1)###MAD (nmol g-1)

One-year monoculture###0.0080.0007c###0.240.01d###41.600.82c###1.380.09b

Two-year consecutive monoculture###0.0210.0009a###0.310.03a###58.121.12a###1.640.18a

Rice -P. heterophylla rotation###0.0110.0011c###0.270.02c###37.780.65c###1.390.09b

Bean -P. heterophylla rotation###0.0170.0006b###0.290.04b###50.010.73b###1.400.26b

Table 4: The quality of P. heterophylla under different cropping patterns

Treatment###Moisture (%)###Water-soluble###Alcohol-soluble###Total ash (%)###Polysaccharide###Total saponin (%)

###extract (%)###extract (%)###(%)

One-year monoculture###8.940.0007a###43.50.0012a###8.460.0051c###3 0.0024a###9.941.6b###0.38130.0042b

Two-year consecutive monoculture###8.370.0007b 43.30.0044a###9.08 0.0031b###3.220.0022a###8.100.14d###0.27770.0075d

Rice -P. heterophylla rotation###7.960.0006c###39.40.0007b###8.790.0019c###3.290.0019a###11.511.9a###0.33170.0076c

Bean -P. heterophylla rotation###8.3 0.0004b###43.70.0083a###10.880.0012a###2.980.004a###8.991.6c###0.5130.0105a

86.8% of one-year monoculture and higher than of two- year consecutive monoculture. The polysaccharides and saponin of bean -P. heterophylla rotation were respectively90.4% and 134% of one-year monoculture. Two rotation patterns could increase medicinal ingredients and alleviatethe effect of continuous cropping obstacle on P. heterophyllaquality (Table 4).

Discussion

Continuous cropping destroyed the protective mechanism of photosynthetic system and reduced non-photochemical quenching coefficient (NPQ) causing light energy absorbed by PSII system not to be used for photosynthesis or dissipated (Zeng et al. 2012). In addition the cell density of leaves and roots declined and leaves emerged abnormal morphology and internal structure which resulted in decline of photosynthetic rate (Zeng et al. 2012). It was found that the chlorophyll content photosynthetic rate stoma conductance intercellular CO2 concentration andtranspiration of one-year monoculture were higher than of two-year consecutive monoculture. It concludes that continuous monoculture significantly reduced leaf photosynthetic capacity of P. heterophylla.The SOD POD CAT activity and MAD contentincreased indicating that protective enzyme system was disturbed membrane lipid was seriously destroyed and growth of P. heterophylla was inhibited in two-year consecutive monoculture. Yu et al. (2003) studied cucumber continuous cropping and found that chlorophyll content transpiration and photosynthetic rate decreased in cucumber leaves of continuous cropping the activity of POD and SOD increased and the growth of leaves was hindered. Other studies on medicinal plants also concludes that continuous cropping had direct negative effect on photosynthetic efficiency root and protective enzymes activity which were major causes of continuous cropping obstacles (Zhang et al. 2010).After crop rotation the chlorophyll content photosynthetic rate and other parameters related to photosynthesis of P. heterophylla were higher than of two- year consecutive monoculture. The total biomass of one- year monoculture increased and activity of protective enzymes MDA content and damage of membrane lipid all decreased which alleviate continuous cropping obstacles of P. heterophylla to a certain extent (Table 3).Crop rotation promoted the recovery of photosynthetic capacity and stability of physiological state in P. heterophylla plant which had positive effect on biomass yield and quality. The yield polysaccharide and saponin contents of rice -P. heterophylla were respectively 92.29%116% and 86.8% of one-year monoculture. Under bean -P. heterophylla rotation the production polysaccharide content and total saponin content of P. heterophylla amounted to 64.79% 90.4% and 134.6% of one-year monoculture. It indicate that rice -P. heterophylla rotation had more significant abatement effect on continuous cropping obstacles than bean -P. heterophylla rotation. And several studies showed the crops rotating with rice have the advantages for soil quality and crop yield such as soybean- rice (Popp et al. 2005) rape-rice (Li et al. 2012b) and wheat-rice rotations (Ma et al. 2013).The results of this study showed that crop rotation could reduce the continuous cropping obstacle to a certain extent and improve the yield and quality of P. heterophylla. However it is very complicated to study mechanisms of continuous cropping obstacles and related abatement which is comprehensive to external performance ofmultiple factors between P. heterophylla and rhizospheresoil. More research through the coordination of different crops rotation are needed which can reduce the accumulation of autotoxic substances and improve the structure and functional diversity of microbial community to restore ecosystem function of rhizosphere soil and overcome the obstacles of continuous cropping. Therefore on the basis of results of field observation and different index measurement further studies for the abatement effect of different cropping patterns on P. heterophylla auto- toxicity and improvement of soil rhizosphere micro- ecological system are needed.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant no. 2012CB126309 U1205021 and 81303170).

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Author:Sheng Lin; Jingjing Huangpu; Ting Chen; Linkun Wu; Zhongyi Zhang; Wenxiong Lin
Publication:International Journal of Agriculture and Biology
Article Type:Report
Date:Oct 31, 2014
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