The primary assessment of the red oak seeds quality and prospects for its bioinvasive potential realization in the Samara region urban environment

Abstract

The world population growth postulates a necessity for food increase to provide mankind with edible products. A growing number of archaeobotanical finds of acorns indicates that they were important as a staple food for some regions. According to its characteristics, red oak is one of the promising species that can increase the resource potential of oak forests in the Middle Volga region. Compared to local oak one, red oak wood is more resistant to vascular and necrotic-cancerous pathologies. The red oak is also more resistant to oak powdery mildew. On the territory of the Middle Volga region, red oak is still rare, because of its limited use in plantations. The subject of the study is the quality of red oak seeds formed by trees from the arboretum of the Institute of Ecology of the Volga Basin (Togliatti city), where they were collected in an amount enough to assess the quality of seeds formed by an introduced species on a territory new to it. The study of the internal structure of oak seeds with dense shells was carried out by digital microfocus radiography using a PRDU installation. This method is included in international standards, primarily for assessing the formation of the seeds internal structure and grain damage by phytophages. X-ray screening allowed to categorize the red oak seeds: 1) seeds, fully formed, filled and not damaged by insects; 2) seeds that, when falling from a tree, retain their cupula (do not have a developed content); 3) seeds damaged by insects during the formation of cotyledons; 4) seeds without a cupula, but with varying severity of underdevelopment; 5) seeds with partial underdevelopment of the cotyledons, which do not fill the entire volume of the seed coats. The weight and size parameters of seeds formed in the Samara region correspond to the indicators from other regions of red oak growth and are: diameter 1,76 0,01 cm; length 2,48 0,02 cm; weight of 1000 seeds 4224 62,65 g (harvest 2021). At the same time, only from 55 to 39% of red oak seeds (harvests in 2021 and 2022, respectively) were of a sufficiently high quality to be used for sowing. Considering the prospects of red oak as an agent of biological invasion, the authors point to the variability of its seed harvest by years, the formation of a high proportion of low-quality seeds, as well as a small amount of self-seedings with increased demands to soil moisture.