Chin J Plan Ecolo ›› 2004, Vol. 28 ›› Issue (1): 39-46.doi: 10.17521/cjpe.2004.0006
• Research Articles •
WANG Qiang, WEN Xiao-Gang, LU Cong-Ming, ZHANG Qi-De
In order to improve rice yields to feed a growing population, China has carried out a `Super High-Yield Rice Project’ since 1996. Tremendous progress was made during the `Ninth Five-Year Plan’and several new varieties of rice hybrids were released. `Hua-an 3’(`X07S’×`Zihui100’) is a new high yield variety that has yields of more than 10 500 kg·hm－2; this compares with yields of 7 500-8 500 kg·hm－2 in the traditional hybrid rice `Shanyou 63‘ (‘Zhenshan 97A‘×‘Minghui 63‘). The photosynthetic functions and pigments of the upper most 5 senescing leaves of the canopy of `Hua-an 3‘ were studied by techniques of fluorescence induction kinetics, low temperature (77K) fluorescence emission spectrum and HPLC. The results showed that the maximal quantum yield of PSⅡ photochemistry (Fv/Fm), efficiency of excitation energy captured by open PSⅡ reaction centers (Fv′/Fm′), quantum yield of PSⅡ electron transport (ΦPSⅡ), photochemical quenching coefficient (qP), and the content of photosynthetic pigments, especially chlorophyll (Chl), neoxanthin (N), lutein (L) and β-carotene (β-Car), of the flag leaf were higher than those of other leaves but its excitation pressure (1-qP) was lower. It was shown that the content of the core antenna complex CP47 in photosystemⅡ (PSⅡ) and photosystem Ⅰ (PS Ⅰ) of the flag leaf also was higher than in other leaves, but the content of its non-active aggregate of light harvesting complex in PSⅡ (LHCⅡ) derived from the Gaussian analysis of low-temperature (77K) fluorescence emission spectra was lower than that of the other leaves. Our research results are as follows: 1) at later growth and development stages of rice, the dry matter of grain was mainly provided by most photosynthesis occurred in the uppermost 3 leaves in the canopy; 2) in the course of leaf senescence, the senescence of photosynthetic reaction centers was quicker than that of the antenna system; 3) one of the photoprotective pathways in hybrid rice may be through an increase in the content of PS Ⅰ, absorption of more light energy, and stimulating a high speed electron transport cycle in order to protect the photosynthetic apparatus under photoinhibitory conditions; 4) in the course of leaf senescence of rice, partial chlorophyll b was probably reduced to chlorophyll a, to decrease the content of LHCⅡ, thus reducing the amount of energy absorbed by LHCⅡ and decreasing the amount of photoinhibitory damage.
WANG Qiang, WEN Xiao-Gang, LU Cong-Ming, ZHANG Qi-De. Photosynthetic Functions of Different Senescing Leaves in the Canopy of Super high-yield Rice ‘Hua-An3’[J].Chin J Plan Ecolo, 2004, 28(1): 39-46.
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