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 te mperature, were studied in relation to regrowth after transfer from day/nig ht temperatures of 16/12 degrees C to 25/20 degrees C. Plants were grown fo r 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 genoty pes after a 45-day growth at 16/12 degrees C was lower than at 25/20 degree s C. When the photosynthesis of plants at 16/12 degrees C was measured at 2 5 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 c ontent 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 sucr ose and, to a lesser extent, starch content was observed. Biomass accumulat ion was also reduced in both genotypes. Transfer from 16/12 to 25/20 degree s C increased photosynthesis, partially restored sucrose but not starch con tent and induced a rapid regrowth in VA-36. Conversely, photosynthesis, car bohydrate content and regrowth remained low in A-619. It is suggested that for the two genotypes, regrowth is dependent on the integrity of the photos ynthetic apparatus which contributes to sensitivity to low temperatures.