Diurnal Variation of Photosynthesis and Its Influencing Factors in Four Cassava Varieties (Lines)

Purpose To clarify the diurnal variation of photosynthesis and its interaction with influencing factors in four new cassava varieties (lines), 1-3-4, SG-2, Shatian (ST), and South China No. 9 (SC9), and to provide a theoretical basis for further guiding the breeding of new varieties (lines) and their northward expansion for increased cultivation area.

Methods A random block field experiment design was used to determine the dynamic changes of key photosynthetic parameters and environmental factors in four cassava varieties (lines).

Results The diurnal variations of the net photosynthetic rate (P_n) and transpiration rate (T_r) of the four new cassava varieties (lines) generally presented a bipeak curve, reaching their peaks around 9: 30 and 13: 30, and all showed a distinct midday depression of photosynthesis at noon. Among them, the average daily P_n ranking of the four new varieties (lines) was as follows: SG-2>SC9>1-3-4>ST. The stomatal conductance and intercellular CO₂ concentration showed a continuous downward trend starting from 7: 30 on a daily basis. The line SG-2 was superior to other varieties (lines) in terms of instantaneous light energy utilization rate and average daily carboxylation efficiency (CE). The P_n of the four varieties (lines) was significantly positively correlated with T_r and CE.

Conclusion The cassava variety SG-2 exhibits superior photosynthetic performance compared to other varieties (lines), with excellent yield and starch content. It has good adaptability and high production potential, making it an ideal germplasm for the northward promotion and cultivation of cassava.