Abstract
There is still a lack of knowledge about the photosynthetic activity of semi-leafless peas and the most important factors determining pea productivity during the growing season. The aim of the study was to evaluate and compare the photosynthetic parameters of three semi-leafless pea varieties in different nutritional backgrounds at different growth stages and to evaluate the relationship between photosynthetic indicators and pea (Pisum sativum L.) seed yield. The test involved three semi-leafless pea varieties, one of which was a new variety, and five NPK fertilization treatments were used, as follows: (1) without fertilizers-NPK 0:0:0, (2) without N fertilizers NPK 0:40:80, (3) NPK 30:40:80, (4) NPK 60:40:80, and (5) NPK 60:80:160. Photosynthetic indicators were assessed three times during the growing season. It was found that the physiological characteristics of peas differed significantly between cultivars and between growing seasons. The most intensive photosynthesis occurred in the middle of pea flowering and slowed down at the end of this stage. According to the photosynthetic characteristic's values (A, gs, Ci), the varieties were arranged in the following descending order: Ieva DS, Simona, Respect. The application of the highest NPK fertilizer rates in most cases resulted in the highest photosynthesis rate, which, compared to the control, increased by 22.8-72.3%. Meteorological conditions in most cases had a significant relationship with physiological indicators.