RELATIONSHIPS BETWEEN CARBON DIOXIDE EXCHANGE RATE, PHOTOSYNTHETIC AREA AND BIOMASS IN PEA

Compensation between carbon dioxide exchange rate per unit photosynthetic area (CER) and total photosynthetic area (TPA) of a plant was examined in field-grown pea (Pisum sativum L.). Eight near-isogenic lines of cv. Alaska, representing all possible phenotypes of the genes af (leaflets transformed to tendrils), st (reduced stipule area) and tl (tendrils transformed to leaflets), were examined. The CER was measured on the leaflets (AfAf), tendrils (afafTlTl) or minute leaflets (afaftltl). The TPA was significantly reduced by the st gene in AfAf types (normal leaflets) with an apparently associated increase in CER. The st gene also significantly reduced the TPA in afaf types but there was no associated increase in CER. Tendrils had a lower CER than normal leaflets and comprised 22% of the TPA of the semi-leafless (afafStStTlTl) type. Crosses were made between a semi-leafless pea and four normal-leafed types previously selected for high or low CER. The CER means (normal leaflets) of the F1 progeny showed va...