Seed productivity of plants in the cenopopulations of species of the genus Tulipa in the conditions of the Republic of Kalmykia

The article deals with the study of the variability of the biometric features of the fruit and the seed productivity of the cenopopulations of Tulipa biflora and T. biebersteiniana in the Republic of Kalmykia. The species are listed in the Red Books in several regions of Russia, in Kalmykia they belong to category III of «rare species». The two cenopopulations of species Tulipa biflora and T. biebersteiniana investigated in the Caspian lowlands grow in the brown desert-steppe alkaline soils; and the three cenopopulations investigated on the Ergeninsky hill (on the territory of Kalmykia) grow in the light chestnut soils of a different degree of alkalinity. In the study period the species showed variability of the biometric features of their fruit depending on the weather conditions during their growing season. Notably, the analysis of the length and width of the boxes shows that in 2018 both parameters of the fruit of T. biflora and T. biebersteiniana were significantly lower and this dynamics is particularly correlated with a decrease in the total precipitation in April, which is the time of active vegetation of both species. The potential seed productivity during the period of the study varied in the cenopopulations of T. biflora from 43.3 to 83.1 pcs. per box, in the cenopopulations of T. biebersteiniana it varied from 59.4 to 109.5 pcs. per box. The actual seed productivity in this period changed from 34.2 to 67.8 pcs. per box in the cenopopulations of T. biflora and from 48.4 to 88.5 pcs. per box in the cenopopulations of T. biebersteiniana. Most of the cenopopulations of T. biflora and T. biebersteiniana have shown a decrease in the seed productivity in 2018 as compared with that in 2017, but in T. biflora this was also accompanied by a decrease in the percentage of seminification, while in T. biebersteiniana, on the contrary, there was an increase in the indicator values. The potential bank of mature seeds (per square m) formed during the growing season in T. biflora cenopopulations, ranged from 253.2 to 3212.8 pieces in 2017 and from 368.0 to 1121.2 pieces in 2018; and T. biebersteiniana cenopopulations it was between 351.2 and 2186.0 pcs in 2017 and between 652.0 and 2719.2 pcs in 2018.