Effects on photosynthesis, carbohydrate accumulation, and regrowth induced by temperature increase in maize genotypes with different sensitivity to low temperature

Photosynthesis and carbohydrate accumulation in maize genotypes (Zea mays L.) VA-36 and A-619, ranked as possessing low and high sensitivity to low temperature, were studied in relation to regrowth after transfer from day/night temperatures of 16/12 degrees C to 25/20 degrees C. Plants were grown for 45 days at 25/20 or 16/12 degrees C, or transferred after 45 days from 16/12 degrees C to 25/20 degrees C for 27 days. Photosynthesis of both genotypes after a 45-day growth at 16/12 degrees C was lower than at 25/20 degrees C. When the photosynthesis of plants at 16/12 degrees C was measured at 25 degrees C it was as high as the photosynthesis of plants at 25 degrees C in VA-36, while it remained lower in A-619. A strong reduction of rubisco content was observed in the sensitive genotype and is suggested as the cause of photosynthesis limitation that was still observed after recovery at 25/20 degrees C. After a 45-day growth at 16/12 degrees C, a reduction of sucrose and, to a lesser extent, starch content was observed. Biomass accumulation was also reduced in both genotypes. Transfer from 16/12 to 25/20 degrees C increased photosynthesis, partially restored sucrose but not starch content and induced a rapid regrowth in VA-36. Conversely, photosynthesis, carbohydrate content and regrowth remained low in A-619. It is suggested that for the two genotypes, regrowth is dependent on the integrity of the photosynthetic apparatus which contributes to sensitivity to low temperatures.