Increased co2 effect on crop production tam 2013-25

1. Submitted by: S. Shaheda Nasreen TAM/13- 25 Increased concentration of Co2 effects on crop production

2. Effect of elevated carbon dioxide on crops Carbon dioxide  is essential to plant growth. Rising CO 2  concentration in the atmosphere can have both positive and negative consequences. Increased CO 2  is expected to have positive physiological effects by increasing the rate of  photosynthesis . ( 'carbon dioxide fertilisation ‘) . Currently, the amount of carbon dioxide in the atmosphere is 380  parts per million and oxygen  is 210,000 ppm . Plant physiological and biochemical responses (Bowes 1993) to elevated CO 2 , known as the CO 2 -fertilization effect ( Dhakhwa et al. 1997), have been studied in plants with different photosynthetic pathways, mostly in C3 species, but also in C4

3. Effects of Rising Atmospheric Concentrations of Carbon Dioxide on Plants Atmospheric concentrations of carbon dioxide have been steadily rising, 315 ppm (parts per million) in 1959 to 385 ppm (Keeling  et al. ,2009). R ising CO 2  concentrations are also likely to have profound direct effects on the growth, physiology, and chemistry of plants, independent of any effects on climate ( Ziska 2008). Our knowledge of plant responses to future CO 2  concentrations rests on the results of experiments that have experimentally increased CO 2  and then compared the performance of the experimental plants with those grown under current ambient CO 2  conditions.

4. Change in climate.

5. Physiological effects of plant due to elevated CO 2 Behavior of stomata Effects on the leaf Effects on photosynthesis & photorespiration Water use and water use efficiency Changes in rooting pattern Effect of CO2 on Nitrogen content Germination Decrease in crop duration Effects on seed yields Consequences on quality of food and forage

6. Effect of stomata Elevated concentrations of CO 2 –partial stomatal closure. Reductions stomatal conductance in crops would translate into reductions of <10% in evapotranspiration , partly because of increases in temperature and decreases in humidity in the air around crop leaves. Due narrowing the stomata has additional benefit that a lesser amount of pollutants in the air will make it through the narrower openings.

7. Effects on the leaf Growing plants at elevated concentration leads to increased leaf area, leaf area index , leaf area duration and leaf thickness as indicated by decreased specific leaf area (SLA) (Bowes 1993; Bray and Reid 2002), which is partly related to the accumulation of non-structural carbohydrates ( Lambers et al. 1998). Accumulation starch increased steadily at a rate of about 6 g/kg dry matter/hour. Elevated CO2 causes plants to produce more number of mesophyll cells and chloroplasts

8. Effects on photosynthesis & photorespiration Photosynthesis :- 6CO 2   + 6H 2 O → C 6 H 12 O 6  + 6O 2 photosynthetic capacity per unit leaf area is increased under CO 2  enrichment. The CO 2  fertilization effect begins with enhanced photosynthetic CO 2  fixation. Non-structural carbohydrates tend to accumulate in leaves and other plant organs as starch, soluble carbohydrates or polyfructosans , depending on species. This may be because the CO 2 -enriched plants do not have an adequate sink (inadequate growth capacity), or lack capacity to load phloem and translocate soluble carbohydrates. Hence Improvement of photoassimilate utilization should be one goal of designing cultivars for the future (Hall and Allen, 1993).

9. Photograph of representative plants that we carefully removed from each of our three experimental units.  The mid- and high-CO 2  plants appear to have nearly identical root systems, while the root system of the low-CO 2  plant is not much smaller.  In terms of aboveground growth, however, there are considerably larger differences .  The low-CO 2  plant is much smaller than the others ; and the plant from the high-CO 2  unit is significantly larger than the plant from the mid-CO 2  unit.

10. Water-use efficiency: effects of CO 2 Water-use efficiency is the ratio of the net gain in dry matter over a given period, divided by the water loss (from the vegetation alone or from soil and vegetation together) over the same period. Stomatal conductance decreases with increasing CO 2  concentration which can cause a reduction of both leaf and whole canopy transpiration. WUE increased with increasing CO 2 due to the decline in ET

11. CO 2 effect on Nitrogen content Plants with nitrogen-fixing symbionts (e.g., peas, beans, alfalfa), under favorable environmental conditions for both symbiont and plant, tend to benefit more For most plants, growth under elevated CO 2  can alter the internal balance between carbon and nitrogen. The content of nonstructural carbohydrates generally increases under high CO 2 , while the concentrations of mineral nutrients and proteins are reduced (Mooney and Koch, 1994; Rogers et al., 1994 ). Decrease in tissue nitrogen is likely due to several factors: Dilution of nitrogen from increased carbohydrate concentrations; Decreased uptake of minerals from the soil, as stomatal conductance decreases and plants take up less water Decreases in the rate of assimilation of nitrate into organic compounds

12. Changes in rooting pattern High carbon gain might increase root length, diameter and number (Lee-Ho et al. 2007), and stimulate lateral root production in plants grown under elevated CO 2 (Pritchard and Rogers 2000). A shift in biomass allocation from leaves to roots can occur under CO 2 enrichment ( Stulen and Den Hertog 1993). longer stems and extended large roots with altered branching patterns (Rogers et al. 1992; Bowes 1993). Root/shoot ratios often increase under elevated CO 2 levels favouring root crops and also contribute to soil organic matter build-up ( Mauney et al., 1992; Mitchell et al., 1993)

13. Decrease in crop duration Duration of crop  growth   cycles  are above all, related to temperature. An increase in temperature will speed up developmen . Sylvan Wittwer , quoted above, states that under most circumstances the availability of CO 2 is the factor which limits growth. Thus with a higher level of CO 2 in the air plants can grow faster with a higher temperature. Germinatio n Increased CO 2 concentration will decrease the rate of germination.

14. Effects on seed yields Reproductive biomass growth as well as vegetative biomass growth are usually increased by elevated CO 2 . However, the harvest index, or the ratio of seed yield to above-ground biomass yield, is typically lower under elevated CO 2  conditions (Allen, 1991; Baker  et al.,  1989), which may also be evidence of the lack of capacity to utilize completely the more abundant photoassimilate . C 3 plants exhibit an increased production averaging about 30% at doubled (700 ppm ) CO 2 concentrations; both biomass and seed production show an increase in almost all experiments under controlled conditions (Cure and Acock , 1986; Rogers and Dahlmann , 1993). Plant growth and yield of soybean were increased by 45% with 1200ppm CO 2 .

15. Quality of food and forage Protein concentrations in plant tissues are closely tied to plant nitrogen status Apart from an overall decrease in N and protein concentrations, as shown under elevated CO 2 , the nutritional value and the quality of the edible products of most food and forage crops are largely unknown. For wheat, barley and rice, the reduction in grain protein ranged from 10% to 15% of the value of ambient CO 2 (315–400 ppm ). Overall decrease for most macronutrients and micronutrients such as Fe, Zn, Mn and Cu under high CO 2 , with nutrient concentrations more affected in straw than in grains, although the responses to elevated CO 2 were species- and cultivar-dependent. Quality of forage crops decreases due higher c:n ratio

16. Rising atmospheric CO 2 may affect oil quality and seed yield of sunflower (Helianthus annus L.) Quality and yield in a sunflower hybrid DRSH 1 and variety DRSF 113, raised inside open top chambers and exposed to elevated CO 2 (550 ± 50 ). Elevated CO 2 exposure significantly influenced the rate of photosynthesis, seed yield and the quality traits in both hybrid and variety. Plants grown under elevated CO 2 concentration showed 61–68 % gain in bio-mass and 35–46 % increase in seed yield of both the genotypes, but mineral nutrient and protein concentration decreased in the seeds. Fatty acid compo- sition in seed oil contained higher proportion of unsatu -rated fatty acids (oleic and linoleic acid) under elevated CO 2 treatment, which is a desirable change in oil quality for human consumption.

17. Positive effects of CO 2 on crop production • Elevated carbon dioxide increases the productivity and water use efficiency of nearly all plants. • Higher levels of atmospheric CO 2 improve, and sometimes fully compensate for, the negative influences of various environmental stresses on plant growth. • Health promoting substances found in various food crops and medicinal plants have been shown to benefit from rising atmospheric CO 2 . • Elevated CO 2 reduces, and frequently completely overrides , the negative effects of ozone pollution on plant photosynthesis, growth and yield. • On the whole, CO 2 -enrichment does not increase the competitiveness of weeds over crops; higher atmospheric CO2 will likely reduce crop damage from insects and pathogenic diseases. • In addition to enhancing forage productivity , atmospheric CO 2 -enrichment will likely not alter its digestibility by animals.

18. Negative effects CO 2 is currently responsible for over 60% of the enhanced greenhouse effect . A new study, the first of its kind, performed by researchers at the University of California, Davis, demonstrated the inhibition of wheat crops to convert nitrate into a protein, due to increased CO2 levels, which affects its nutritional value. Increased CO 2 concentration will decrease the rate of germination Food quality is declining under the rising levels of atmospheric carbon dioxide that we are experiencing The results showed that not only are amino acids like protein affected, but trace elements as well as, There was a 14 percent increase in lead and an eight percent drop in the iron content of the crop. If carbon dioxide levels continue to rise and negatively effect plants and crops, the amount of food proteins in the whole world could drop as much as three percent in just a few decades. There are already people all around the world without enough food or proper nutrition, especially protein.

19. Effect of CO 2 on C3 and C4 plants Experiments concerning crop performance at elevated CO 2 concentrations in general show a positive but variable increase in productivity for annual crops (Kimball, 1983; Strain and Cure, 1985; Cure and Acock , 1986; Allen et al) C3 plants exhibit an increased production averaging about 30% at doubled (700 ppm ) CO 2 compaired to C4 plants 49% for C3 cereals, 20% for C4 cereals and 15% for CAM plants ( Idso and Idso , 2000). The extent and occurrence of physiological adaptations of the photosynthetic apparatus, particularly of perennial plants, to long-term exposure to high CO 2 concentrations—which is more directly relevant to long-term climate change—are still unreported.

20. Graph showing effect on photosynthesis

21. The Effect of Temperature on Plant Response to Higher Levels of CO 2 Duration of crop  growth   cycles  are above all, related to temperature. An increase in temperature will speed up development . In the case of an annual crop, the duration between  sowing  and  harvesting  will shorten (for example, the duration in order to harvest corn could shorten between one and four weeks). The shortening of such a cycle could have an adverse effect on productivity because  senescence  would occur sooner.

22. It is seen that the extra CO 2 increases the optimum temperature for net photosynthesis by about 11 o C: from 25 o C in air of 325 ppm CO 2 to 36 o C in air of 1935 ppm CO 2 The CO2 – Temperature- Growth interaction

23. IPCC (FACE) The most widely used experimental system is the open-top chamber. Free-air CO2 enrichment (FACE) experiments are more expensive but attempt to create conditions close to those likely to be experienced in an open field . Initial results from these experiments confirm the basic positive response of crops to elevated CO2 but studies have been conducted only for a few crops ( Mauney et al., 1992). Crop traits are selected and bred into different varieties to produce high yields for different climate and resource conditions. The separate and combined effects of elevated CO2 and high temperature on plants have been studied , either in growth chambers, in greenhouses or in the field

24. Free-air carbon dioxide enrichment (FACE) allows experiments with controlled atmospheric concentrations of carbon dioxide to be conducted in the field phytotrons

25. FACE system The FACE system has six octagonal plots located in different places having similar soils and agronomic histories. Three plots were randomly allocated for the elevated CO 2 treatments (hereinafter called FACE plots) and the other three for the ambient treatments (hereinafter referred to as ambient plots). In the FACE plots, the plants were grown within 14-m-diameter ‘rings’ which sprayed pure CO 2 both day and night towards the plot centre from eight peripheral emission tubes (5mlong) located about 0.5m above the canopy (Okada, 2001). The ambient plots had no ring structures, and plants were grown under ambient [CO2] without ring structures. The target [CO2] in the FACE plots throughout the growth season was controlled to 200 mmol /mol above that of ambient by computer system platform.

26. Elevated CO 2  also leads to changes in the chemical composition of plant tissues . Due to increased photosynthetic activity , leaf nonstructural carbohydrates (sugars and starches) per unit leaf area increase on average by 30–40% under FACE elevated CO 2  (Ainsworth 2008; Ainsworth & Long 2005 ). Leaf nitrogen concentrations in plant tissues typically decrease in FACE under elevated CO 2 , with nitrogen per unit leaf mass decreasing on average by 13% (Ainsworth & Long 2005). Crop yield in FACE also appears to be enhanced by elevated CO 2  to a lesser extent under low-N than under high-N (Ainsworth & Long 2005; Ainsworth 2008; Long  et al.  2006).

27. Estimated future level of CO 2 year CO 2 ppm 2015 389-399 2050 463-623 2100 700-1099

28. Adaptation / mitigation actions could include the following: 1. Selection of plants that can better utilize carbohydrates and produce less structural matter and more reproductive capacity under CO 2  enrichment . 2. Search for germplasms that are adapted to higher day and night temperatures, and incorporate those traits into desirable crop production cultivars to improve flowering and seed set. 3. Change planting dates and other crop management procedures to optimize yields under new climatic conditions. 4. Shift to species that have more stable production under high temperatures or drought. 5. Determine whether more favourable N:C ratios can be attained in forage cultivars adapted to elevated CO 2 . 6. Where needed, and where possible, develop irrigation systems for crops.

29. 7. Micro-algae can fix carbon dioxide from different sources, which can be categorised as: CO2 from the atmosphere. CO 2 from industrial exhaust gases (e.g., flue gas and flaring gas). Fixed CO 2 in the form of soluble carbonates (e.g., NaHCO3 and Na2CO3). Can be grown in closed systems, which could result in savings of precious freshwater resources.

30. Summary and conclusions Elevated CO 2   increases the size and dry weight of most C 3  plants and plant components. The harvest index tends to decrease with increasing CO 2  concentration and temperature . Selection of plants that could partition more photoassimilates to reproductive growth should be a goal for future research . C 4  plants include most tropical and sub-tropical grasses and several important crops, including maize (corn), sugar cane, sorghum, and the millets. There has therefore been considerably more research on the responses to elevated CO 2  in C 4  than in CAM plants.

31. Rising CO 2  over the next century is likely to affect both agricultural production and food quality. Elevated CO 2  concentration generally compensates for the negative effects of warming temperatures on production. Moreover, positive effects of elevated CO 2  concentration on grain yield increase with warming temperatures. The findings could be critical for climate change-driven agricultural production that ensures global food security.

32. Thank you....