The influence of abiotic factors on the growth and development of parsnip plants

The main drivers influencing plant growth, yield increase and its quality characteristics are biotic and abiotic factors. Combinations of abiotic stresses, such as drought and heat, have a much greater impact on yields and product quality. Plants' response to these stresses can vary depending on the species and different stages of development. Understanding the mechanisms and how they protect plants from stress has become vital for improving the yield and quality of parsnip products in changing climates. The purpose of the study was to determine the influence of abiotic factors (temperature and precipitation) on the yield, duration of phenological phases of growth and development of plants, the dynamics of leaf and root mass growth of parsnip in the conditions of the Right-Bank Forest-Steppe of Ukraine. The research was carried out in the field experiment of the Department of Vegetable Growing and Closed Ground in the National Research Institute “Fruit and Vegetable Garden” of NUBiP of Ukraine within the conditions of the Right-Bank Forest-Steppe of Ukraine during 2015-2017. The area of the registered plot was 11.3 m2, and the repetition rate of the experiment is four times. The placement of variants is systematic. The research found that the shortest sowing-emergence period lasted 16 days in the variants sown in the 3rd ten-day period of May and the 1st ten-day period of June. A significant delay of 21 days in this period was noted for sowings from 1st to 3rd ten-day periods of April. The duration of the period from the beginning of root crop formation to bunch ripeness was the shortest when sown in the 1st ten-day period of April – 28 days, and the longest when sown in the 1st ten-day period of June – 51 days. The growing season ranged from 110 to 165 days and was characterised by GDD (> 10 °C) of 1102.4-1439.0 °C and precipitation of 128.1-225.2 mm. After sowing in April, intensive growth of root crops from 2.9 to 3.5 g / day was observed in the second half of August. After sowing in May, the greatest increase in root crops from 2.1 to 2.7 g/day was noted in the first half of September. Thus, for sowings in the 1st ten-day period of June, this figure was the highest in the second half of September (1.9 g/day). The variant sown in the 1st ten-day period of April provided a high yield of root crops of 50.3 t/ha, which is 5.3 t/ha or 11.8% significantly more than the control variant. When sowing in the following terms, a significant decrease in yields was observed compared to the control, namely: for 3rd ten-day period of April – by 3.5 t/ha, or 7.7%, for 1st ten-day period of May – by 8.8 t/ha, or 19.6%, for 2nd ten-day periods of May – by 17.4 t/ha, or 38.6%, for 3rd ten-day periods of May – by 23.0 t/ha, or 51.1%, for 1st ten-day period of June – by 31.7 t/ha, 70.6% compared to the control. A strong direct correlation (r = 0.74-0.99) was found between the growing season and yield, root mass, marketability, and biochemical parameters, namely: dry matter, dry soluble matter, sugars, vitamin C. An inverse correlation (r = -0.98) was observed between the duration of the growing season and nitrates. Increasing the growing season by 10 days increases the yield up to 6.9 t/ha, marketability up to 2.7%, root weight up to 31 g, dry matter content up to 0.7%, dry soluble matter up to 0.3%, sugars up to 0.5%, vitamin C up to 0.8 mg/100 g and reduces the nitrate content to 8.4 mg/kg. Leaf area, photosynthetic potential, and net photosynthetic productivity are strongly directly related (r = 0.92-0.98) to yield. For increasing the leaf surface area to 1.0 thousand m2 the yield is also growing up to 0.7 t/ha. Increasing the photosynthetic potential to 0.05 million m2 days/ha increases the yield to 0.2-1.2 t/ha. Also, the yield increases to 0.3-0.7 t/ha with an increase in net photosynthetic productivity to 0.05 g/m2 per day. The molecular knowledge on plant responses to abiotic stress is promising for further study and is likely to advance crop resilience to climate change and increase the economic efficiency of production