| Abstract: | Grange, R. I. 1987. Carbon partitioning in mature leaves ofpepper: Effects of transfer to high or low irradiance.—J.exp. Bot. 38: 77–83. Pepper plants were grown at an irradiance of either 55 W m–2or 90 W m–2 PAR. Changes in net photosynthesis, carbonexport, starch and sugar contents in a single mature leaf weremeasured at intervals for 8 d following transfer of plants betweenthe two irradiances. On transfer from low to high irradiance,the net photosynthesis rate increased immediately but exportrate increased only slowly, to a maximum after 3 d. While assimilationexceeded export more starch and sucrose accumulated in the dayand remained in the leaf at the end of each night. Hexose contentsat the end of night remained low and constant, but the daytimemaximum rose during the first 2 d from transfer, thereafterreturning to pre-transfer contents. Following transfer of leaves from high to low irradiance starchpresent in the leaf provided sufficient reserves to maintainthe rate of export for one day. Subsequently, the sucrose contentfell and the export rate declined to near that in leaves grownin low irradiance. Sucrose and hexose accumulation following transfer from lowto high irradiance suggests a limitation to export ‘downstream’from sucrose synthesis, probably in the loading step from mesophyllto phloem. Key words: Pepper, export, starch, loading |
