A possible scenario for the end of the 21st century is that the atmospheric CO2 concentration will be in the range of 510 - 760 μl·L -I and that the mean global temperature will be 1.5°C - 4.5°C higher than present day. One of the pre-eminent manifestations of climate change is the increase in atmospheric CO2 concentration. Both CO2 and temperature are the key variables of global climate and may cause significant changes in crop productivity. An experiment was conducted inside open top chamber (OTCs) in kharif season 2014 to evaluate the effects of CO2 enrichment and temperature rise with condition OTC1 (ambient condition), OTC2 (25% higher CO2 than ambient), OTC3 (25% higher CO2 + 2°C > ambient temperature) and OTC4 (2°C >ambient temperature) on physiological traits and yield of rice genotypes to identify the suitable genotypes for changing climatic conditions. The study revealed that rice genotypes performed better under elevated CO2, with slight changes in development, such as growth and in yield attributing traits, depending on the genotypes. However, the beneficial direct impact of elevated (CO2) on crop yield can be counteract by elevated temperatures. Rice genotype IR83376-B-B-24-2 was highly responsive while IR84895- B-127-CRA-5-1-1 was least responsive toward elevated CO2. Physiological traits like relative water content (RWC %), membrane stability index (MSI %), chlorophyll content, photosynthetic rate and TSS content were improved under elevated CO2. However, responses of these traits were negative with elevated temperature. We point out that studies related to changes in crop physiology and *Corresponding author. S. K. Dwivedi et al. 2340 yield as a consequence of global climatic changes should be a priority due to their association with food security.
One of the greatest manifestations of climate change is the increase in atmospheric CO2 concentration. During the last twelve years, the rate of increase of CO2 is 1.9 ppm yr−1 and is forecasted to be as high as 570 ppm by the middle and may reach 700 ppm or more by the end of this century [
This study was conducted in the experimental farm of ICAR Research Complex for Eastern Region, Patna located at 25˚35'37"N latitude and 85˚05'E longitude and at an altitude of 51.8 m above mean sea level. The land area of open-top chambers (OTCs) had a level topography. The climate of the experimental site is semi-arid with dry hot summer and mild winters. The crop season of rice crop is from July to Oct. (kharif season). The soil at the experimental site belongs to the major group of Indo-Gangetic alluvium (
Year | Sand (%) | Silt (%) | Clay (%) | Organic carbon (%) | Soil pH | Bulk density (mg/m3) | Electrical conductivity (dSm−1) | Available nitrogen (kg/ha) | Available phosphorus (kg/ha) | Available potassium (kg/ha) |
---|---|---|---|---|---|---|---|---|---|---|
2013-14 | 29.5 | 41.5 | 28.0 | 0.67 | 7.3 | 1.45 | 0.26 | 237 | 27.0 | 203.2 |
Four rice genotypes (R. Bhagwati, IR64, IR83376-B-B-24-2 and IR84895-B-127-CRA-5-1-1) were evaluated inside open top chambers (OTCs) at ICAR-RCER, Patna, in Kharif season 2014 with an objective to assess the impact of elevated CO2 and temperature (2˚C ˃ ambient) on morpho-physiological traits and yield. The treatment condition in each OTC was OTC1 (ambient condition), OTC2 (25% higher CO2 than ambient), OTC3 (25% higher CO2 + 2˚C ˃ ambient temperature) and OTC4 (2˚C ˃ ambient temperature). Fields (inside the OTCs) were dry ploughed and leveled but not puddled during land preparation. Twenty one days (21 days) old seedlings from wet bed nursery were transplanted at the rate of 2 seedlings per hill at a spacing of 20 cm × 15 cm in plots. In each plot a uniform plant stand was maintained and standard agronomic practices were followed for raising and maintenance of plants. Plots were fertilized at the rate of 90:60:40 kg N:P:K ha−1. Nitrogen was applied on three occasions (1/3each at sowing/transplanting as a basal, at 30 days and at 60 days after transplanting), while the P2O5 and K2O were applied as a basal application. The experimental plots were kept weed free by hand weeding. Three replications were maintained for each genotype in each open top chamber. Replications were randomized within the OTCs. The plot size for each replication was 1 m2 and about 33 plants per square meter were available. The observations were recorded on ten randomly selected plants per genotype per replication for all the traits, plant height (cm), as well as grain yield (t/ha).
All the OTCs were equipped with humidity, temperature and CO2 sensors. Each open top chamber was divided into four equal quadrants with water proof brick partitioning. In each quadrant 3 replications were maintained. Pure CO2 (99.7%, v/v CO2 and less than 10 ppm CO) was released from a commercial grade cylinder fitted with a regulator. Carbon dioxide concentration of air within the elevated CO2 chambers was maintained around the target concentration by a PC-based real-time data acquisition and control (DAC) system designed based on the principles described in [
Daily maximum and minimum temperatures, maximum and minimum relative humidity, daily rainfall were recorded from the meteorological observatory of the ICAR Research Complex, Patna. Mean daily maximum and minimum temperatures and relative humidity (RH) inside the OTC were recorded using data-logger (
Rice plants with uniform development process were tagged in each replication at heading stage in each plot. Tagged plants of three hills from each plot were sampled at anthesis stage, with flag leaves removed from plants for physiological parameter measurements as follows:
Leaf relative water content (RWC %) was estimated by recording the fresh weight, turgid weight of 0.5 g fresh leaf samples by keeping in water for 4 h, followed by drying in hot air oven till constant weight was achieved [
Membrane stability index (MSI %) was estimated as per [
Estimation of chlorophyll content in plants is based on the absorption of light by chlorophyll extracts prepared by incubating the leaf tissues in DMSO (Dimethyl sulfoxide). DMSO renders plasmalemma permeable thereby, causing the leaching of the pigments [
Total chlorophyll = (20.2 × OD645 + 8.02 × OD663) × V/1000 × w
Rate of photosynthesis was measured on leaves using portable Infrared Gas Analyzer (IRGA LI-6400 Model). The rate of photosynthesis was measured by operating the IRGA in the closed mode. The photosynthetic rate was determined at anthesis stage in the upper most fully expanded leaf between 10 a .m and 11.30 a .m by providing artificial light source of light intensity 1200 µmol∙m−2∙S−1. The net photosynthetic rate was expressed as µmol∙m−2∙s−1.
Total sugar was determined the by Anthrone reagent method [
One ml of sugar sample was taken and to this 4 ml solution of anthrone regent was added. The mixture is heated on a boiling water bath for 8 min followed by cooling. The optical density of green to dark green colour was read at 630 nm in UV-visible spectrophotometer (model Specord Bio-200, Analytik Jena, Germany). A blank and two freshly prepared glucose standards were also included with each set of samples.
The data were analyzed statistically using factorial complete randomized design (CRD) and CD at 5% (p = 0.05) and ANOVA were calculated. The analysis was done using Statistics 8.1 software programme.
The concentration of CO2 changed from morning to evening. The concentration of CO2 was higher during morning hour after that due to increase in consumption by plants as the day progresed led to decrease in concentration inside the OTCs. Moreover, during evening hour the concentration of CO2 again rises (
Relative water content of rice genotypes was measured to assess the water status of the plants inside open top chambers (
Days after transplanting | OTC 1 | OTC 2 | OTC 3 | OTC 4 | Field condition |
---|---|---|---|---|---|
45 DAT | 28.3 | 28.7 | 31.0 | 30.2 | 28.0 |
60 DAT | 28.1 | 28.5 | 30.1 | 29.8 | 27.3 |
75 DAT | 29.4 | 29.7 | 31.3 | 30.7 | 28.9 |
Membrane stability index (%) was measured to assess the stability of the cell membrane of the plants leaf inside open top chambers under elevated CO2 and temperature condition (
The mean chlorophyll content was increased under elevated CO2 across the genotypes while there was decline in mean chlorophyll content under elevated temperature condition (
Bhagwati grown under elevated CO2 conditions showed enhancement in chlorophyll content by around 24% and 23% while there was decline in chlorophyll content by around 16% and 15% when grown under elevated temperature. While, in IR84896-B-127-CRA-5-1-1 and IR 64 it was 6% and 12%, respectively. However under elevated temperature condition the decline in chlorophyll content in rice genotypes IR84895-B-127-CRA-5-1-1 and IR 64 was 27% and 18%, respectively. [
Study revealed that photosynthetic rate of rice genotypes under elevated CO2 treatment was significantly (p < 0.05) greater than the ambient condition (
across the genotypes, however rice genotypes IR83376-B-B-24-2 was least affected due to elevated temperature. Elevated temperature have pronounced negative effect on the genotypes IR84895-B-127-CRA-5-1-1 and showed maximum decline (32%) in photosynthetic rate as compared to ambient condition. [
Total soluble sugar content of the elevated CO2 treatment was significantly (p < 0.05) greater than the control OTC at all times (
Results revealed that yield and yield attributes traits of all the genotypes of rice showed positive response with elevated CO2 and negative with elevated temperature (
Cultivar | Treatment | Plant height (cm) | Panicle length (cm) | Grains panicle−1 | 1000 grain weight (g) | Grain yield (t∙ha−1) | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
R. Bhagwati | Ambient CO2 | 129 | 28.12 | 198 | 22.19 | 3.91 | ||||||||||
Elevated CO2 (25% higher > Ambient | 137 | 30.48 | 215 | 23.90 | 4.52 | |||||||||||
Elevated CO2 + Elevated Temp (2˚C) | 157 | 29.94 | 207 | 22.91 | 4.26 | |||||||||||
Elevated Temp (2˚C) > Ambient | 149 | 27.96 | 194 | 17.48 | 3.19 | |||||||||||
IR64 | Ambient CO2 | 132 | 28.56 | 218 | 23.68 | 3.78 | ||||||||||
Elevated CO2 (25% higher > Ambient | 142 | 30.74 | 242 | 25.03 | 4.23 | |||||||||||
Elevated CO2 + Elevated Temp (2˚C) | 160 | 29.46 | 219 | 24.14 | 4.02 | |||||||||||
Elevated Temp (2˚C) > Ambient | 155 | 28.6 | 198 | 18.69 | 3.42 | |||||||||||
IR83376-B-B-24-2 | Ambient CO2 | 153 | 31.32 | 228 | 24.09 | 4.18 | ||||||||||
Elevated CO2 (25% higher > Ambient | 166 | 35.14 | 245 | 27.01 | 4.81 | |||||||||||
Elevated CO2 + Elevated Temp (2˚C) | 177 | 32.16 | 233 | 25.08 | 4.49 | |||||||||||
Elevated Temp (2˚C) > Ambient | 170 | 28.96 | 231 | 20.52 | 3.9 | |||||||||||
IR84895-B- 127-CRA-5-1-1 | Ambient CO2 | 93 | 19.88 | 109 | 21.77 | 3.56 | ||||||||||
Elevated CO2 (25% higher > Ambient | 95 | 20.42 | 115 | 22.07 | 3.88 | |||||||||||
Elevated CO2 + Elevated Temp (2˚C) | 104 | 20.14 | 113 | 22.04 | 3.70 | |||||||||||
Elevated Temp (2˚C) > Ambient | 103 | 19 | 104 | 17.10 | 2.91 | |||||||||||
Factors | O | V | OXV | O | V | OXV | O | V | OXV | O | V | OXV | O | V | OXV | |
LSD (p = 0.05) | 3.57 | 3.57 | 7.14 | 1.14 | 1.14 | 2.29 | 8.97 | 8.97 | 17.94 | 0.53 | 0.53 | 1.06 | 0.10 | 0.10 | 0.20 | |
SEm+ | 1.78 | 1.78 | 3.57 | 0.57 | 0.57 | 1.15 | 4.49 | 4.49 | 8.98 | 0.24 | 0.24 | 0.49 | 0.04 | 0.04 | 0.09 | |
CV (%) | 4.06 | 6.60 | 7.39 | 2.23 | 2.47 |
O―OTC; V―Variety; OXV―Interaction.
elevated temperature. [
Improved physiological traits (RWC, membrane stability, chlorophyll content, photosynthetic rate and TSS) may benefit rice genotypes under elevated CO2 and temperature conditions. By virtue of greater membrane stability and photosynthetic rate, IR83376-B-B-24-2 and Rajendra Bhagwati may be assumed as tolerant among the studied rice genotypes for growing in changing climatic conditions. Since rice is a staple food crop, long term studies may provide better understanding on the efficiency of such genotypes which are increasingly associated with food security.
Sharad KumarDwivedi,SantoshKumar,VedPrakash,SurajitMondal,Janki SharanMishra, (2015) Influence of Rising Atmospheric CO2 Concentrations and Temperature on Morpho-Physiological Traits and Yield of Rice Genotypes in Sub Humid Climate of Eastern India. American Journal of Plant Sciences,06,2239-2249. doi: 10.4236/ajps.2015.614237