Diurnal changes in leave photosynthesis at the late development stage o f winter wheat were examined.The results indicated that the photosynthetic rate was parallelly changed with,but not totally dependent on the vari...Diurnal changes in leave photosynthesis at the late development stage o f winter wheat were examined.The results indicated that the photosynthetic rate was parallelly changed with,but not totally dependent on the variation of st omatic conductance.At 10∶00 am, the photosynthetic rate reached its highest le ve l,then gradually decreased along with the stomatic conductance.Before 12∶00 am, the decrease in photosynthetic rate was mainly caused by stomatic limitation s.Following it,stomatic limitations (Ls) were decreased,and the intercellu ler CO 2 concentration (Ci) was increased.Inhibition of photosynthesis,in cluding the decrease of leaf photosynthetic capacity (J max ) and Rubisco ca rboxy lic activity and efficiency (A/Ci) was mainly resulted from nonstomatic limitations,not stomatic limitations.展开更多
Three winter wheat cultivars ( Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features w...Three winter wheat cultivars ( Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features were investigated. Daily changes of net photosynthetic rate (P-n), transpiration (T-r) in different growth stages were measured in order to find the relationship between leaf photosynthesis and yield. Instantaneous water use efficiency (WUE) of leaf was calculated from P-n/T-r. It is suggested that relationship between photosynthetic rate and yield changed with the developing stages of wheat. High yield wheat cultivar Jingdong 8 (released in the 1990s) had a higher photosynthetic rate ( the maximal P-n increased by 77%) and transpiration rate (the maximal T-r increased by 69%), but a lower WUE than the low yield cultivar Yanda 1817 (released in the 1940s) during the day time at stem elongation stage. However; difference of P-n among the three cultivars changed with wheat growth process. Before 10 o'clock P-n in leaves of Jingdong 8 usually was the highest of the three cultivars, but P-n of Yanda 1817 was the highest after 10 o'clock. At dough ripe stage, P-n in leaves of Yanda. 1817 was the highest among the three cultivars during the whole day. The difference of changing trend of transpiration in three wheat cultivars was similar to P,, but WUE of Yanda 1817 was the highest in those three cultivars, indicating that the higher yield of Jingdong 8 was achieved via a greater consumption of water. Contrary to the cultivars released in the later period, midday depression of photosynthesis was small in Yanda 1817, which might suggest that Yanda 1817 was resistant to photoinhibition. It is possible that photosynthetic potential in leaves of wheat increased as wheat cultivars was improved over the past six decades. However, it became less resistant to photoinhibition.展开更多
文摘Diurnal changes in leave photosynthesis at the late development stage o f winter wheat were examined.The results indicated that the photosynthetic rate was parallelly changed with,but not totally dependent on the variation of st omatic conductance.At 10∶00 am, the photosynthetic rate reached its highest le ve l,then gradually decreased along with the stomatic conductance.Before 12∶00 am, the decrease in photosynthetic rate was mainly caused by stomatic limitation s.Following it,stomatic limitations (Ls) were decreased,and the intercellu ler CO 2 concentration (Ci) was increased.Inhibition of photosynthesis,in cluding the decrease of leaf photosynthetic capacity (J max ) and Rubisco ca rboxy lic activity and efficiency (A/Ci) was mainly resulted from nonstomatic limitations,not stomatic limitations.
文摘Three winter wheat cultivars ( Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features were investigated. Daily changes of net photosynthetic rate (P-n), transpiration (T-r) in different growth stages were measured in order to find the relationship between leaf photosynthesis and yield. Instantaneous water use efficiency (WUE) of leaf was calculated from P-n/T-r. It is suggested that relationship between photosynthetic rate and yield changed with the developing stages of wheat. High yield wheat cultivar Jingdong 8 (released in the 1990s) had a higher photosynthetic rate ( the maximal P-n increased by 77%) and transpiration rate (the maximal T-r increased by 69%), but a lower WUE than the low yield cultivar Yanda 1817 (released in the 1940s) during the day time at stem elongation stage. However; difference of P-n among the three cultivars changed with wheat growth process. Before 10 o'clock P-n in leaves of Jingdong 8 usually was the highest of the three cultivars, but P-n of Yanda 1817 was the highest after 10 o'clock. At dough ripe stage, P-n in leaves of Yanda. 1817 was the highest among the three cultivars during the whole day. The difference of changing trend of transpiration in three wheat cultivars was similar to P,, but WUE of Yanda 1817 was the highest in those three cultivars, indicating that the higher yield of Jingdong 8 was achieved via a greater consumption of water. Contrary to the cultivars released in the later period, midday depression of photosynthesis was small in Yanda 1817, which might suggest that Yanda 1817 was resistant to photoinhibition. It is possible that photosynthetic potential in leaves of wheat increased as wheat cultivars was improved over the past six decades. However, it became less resistant to photoinhibition.
