Morphogenesis and vitality of seedlings of Ginkgo biloba in outdoor conditions

Abstract

Ginkgo biloba L. is a relic tree that is preserved in natural conditions only in China. In the North-East Ukraine ginkgo is only in the process of introduction, but in certain places ginkgo trees are grown for decorative purposes which show high vitality. Therefore a relevant and promising task is the creation of industrial plantations of ginkgo for collection of its leaves. The objective of the study was morphological peculiarities of ginkgo plants and their vital condition depending on the calendar age of the seedlings at the stage when they were transplanted into the soil. For growing ginkgo, in our studies, a combined two-stage system was approbated, accor­ding to which seedlings were grown in greenhouses during 2–3 years, and then moved into soil outdoors. In our study, as planting material we used seedlings of ginkgo from a plant nursery (greenhouse) of Sumy National Agrarian University planted in 2014 and 2015. Seedlings were planted in the soil in early spring. Seedlings for growth completion were planted in rows with inter-row distance of 0.8 m and distance between the plants measuring 2.5–3.0 m. We studied the condition of the seedlings in two variants: variant 1 – three-year old seedlings obtained in the greenhouse were transplanted in spring 2018; variant 2 – two-year old seedlings obtained in greenhouse were transplanted in spring 2017. Comparative morphometric analysis and evaluation of vitality of these plants was performed in August 2019. Both groups of seedlings were five years old at the time of survey. For evaluation of morphometric structure of the ginkgo seedlings and their vital condition we used randomized selections of specimens in amount of up to 30 from plantations of variants 1 and 2. Analysis of the plants was conducted during the end of the vegetative period of 2019, when active growth of the plants stopped. Four main parameters of the plants were recorded: height, value of annual increment, diameter of the stem near the root neck and the number of leaves. Vital condition of the seedlings was evaluated on the basis of algorithm of vital analysis. Vitality of each seedling was evaluated by the coefficient of Q vitality, value of which was in interval from 0 to 1.0. Depending on the value of Q the seedlings were divided into five classes of vitality: 0–0.2 – cc (specimens of the lowest vitality), 0.2–0.4 – c (low vita­lity), 0.4–0.6 – b (average vitality), 0.6–0.8 – a (high vitality), 0.8–1.0 – aa (specimens with highest vitality). Comparative analysis of morphological peculiarities of the ginkgo seedlings revealed that two-year plants transplanted outdoors from the greenhouse had higher annual increment of the main stem, diameter of stem and number of leaves. Vital condition of such seedlings was the highest and was evaluated using Q index, which ranges between vitality of classes b to aa. This allows recommending a two-stage scheme of growing seedlings of ginkgo in North-East Ukraine. The optimum age for transplanting seedlings from greenhouses to open soil is two years.