Response of rice to p(CO2) enrichment: the relationship between photosynthesis and nitrogen metabolism
Rice (Oryza sativa L.) is grown in many different agro-ecological zones and it assimilates CO 2 directly through C 3 photosynthesis. At current CO 2 partial pressure [p(CO 2 )], rice is not photosynthetically saturated but immediately after exposure to 100 p(CO 2 ), photosynthetic rates are increase...
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Published in | Journal of crop improvement Vol. 13; no. 1-2; pp. 31 - 53 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Taylor & Francis Group
01.01.2005
|
Subjects | |
Online Access | Get full text |
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Summary: | Rice (Oryza sativa L.) is grown in many different agro-ecological zones and it assimilates CO
2
directly through C
3
photosynthesis. At current CO
2
partial pressure [p(CO
2
)], rice is not photosynthetically saturated but immediately after exposure to 100 p(CO
2
), photosynthetic rates are increased by 48 percent on an average. However, this increase is not sustained during prolonged exposure and is associated with reduced amounts of ribulose-1-5-bisphospate carboxylase/oxygenase (Rubisco) content and its maximum potential activity (V
cmax
). Rubisco content and V
cmax
were reduced by 33 and 22%, respectively, at elevated p(CO
2
) and this has an additive effect on leaf photosynthesis.
Activation state of the Rubisco is also decreased by elevated p(CO
2
) but no deactivation of Rubisco occurs in rbc S antisense rice with 40% wild type Rubisco suggesting that deactivation is an optimize response. Large amounts of Rubisco (about 80-90%) is synthesized prior to full expansion of leaf when sugar accumulation is minimal. After the leaf has fully expanded, very little Rubisco (about 10-20%) is synthesized and a large amount of sugar accumulates during this period. Therefore, it is unlikely that downregulation of Rubisco at elevated p(CO
2
) is caused by decreasing the mRNA transcripts for Rubisco small subunit (rbcS) and Rubisco large subunit (rbcL) through soluble sugars. It is more likely that elevated p(CO
2
) mediated decline in Rubisco is due to rapid degradation of protein and lower nitrogen (N) allocation to Rubisco due to reduced N afflux. Leaf N content was reduced by 16% in plants grown at elevated p(CO
2
) though leaf N to Rubisco ratio remained consistently unchanged regardless of growth p(CO
2
) suggesting that N assimilation, distribution and remobilization at the whole plant level is tightly controlled at elevated p(CO
2
). Further, changes in N and C metabolisms at elevated p(CO
2
) are likely to reduce the critical N concentration by 30% at elevated p(CO
2
). |
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Bibliography: | http://www.haworthpress.com/web/JCRIP/ |
ISSN: | 1542-7528 1542-7536 |
DOI: | 10.1300/J411v13n01_03 |