BIOLOGICAL PECULIARITIES OF SOME REPRESENTATIVES OF THE RUTACEAE FAMILY IN CONDITIONS OF THE DNU BOTANICAL GARDEN

Abstract

In the open field citrus grow only in the southern regions of Ukraine, where the combination of heat and moisture makes them a successful growing season.Adaptive gardening questions are particularly relevant in Ukraine, where environmental factors restrict the variety of crops grown and the stability of their fruiting. Taking into account the biological characteristics of the species and varieties and the study of some environmental factors (light, temperature and water regimes, causing the plant to the generative development it is possible to grow citrus outside of the subtropics in special constructions.

Thereby, the aim of the study was to study the biological characteristics of growth and fruiting of citrus, as well as a selection of perspective variety of grapefruit (Citrus paradisiMarf.), Orange (Citrus cinensisOsb), lemon (Citrus limon L.), kinkana (FortunellaSwingle ) mandarin - (Citrus reticulata Blanco) which are suitable for cultivation in the greenhouse of the DNU Botanical garden  in natural light.

It was assumed the following tasks:

• to determine the dynamics of temperatures throughout the year;
• to identify the timing and duration of passage of the main phenological phases;
• to conduct biometric measurements of aboveground parts;

The main experimental work carried out in 2015-2016 in greenhouse conditions of the Dnepropetrovsk Botanical garden. All records and observations were carried out in accordance with the requirements of the methodology of experimental work, according to the standard methods.

Phenological observations were conducted on all species and varieties. The observations were carried out during the vegetation through a day.

In December, using the measuring rods in all the studied plants were measured the height of trees, width along and across rows. The increase in trunk diameter was measured by caliper, at a 20 cm height from the root collar. The amount of increase was determined by linear measurements of all of the shoots. The average length of the shoots was determined by dividing the amount of increase in number of shoots. The leaf area was determined by the conventional method.

The statistical processing of the results was carried out. The results of experiments processed at the 95% level of confidence.

According to our results the annual cycle of growth and development of citrus plants (phenophases) in our environment occur at different times, depending on the species, varietal characteristics and climatic conditions of different years. They can either increase or decrease, while the difference can reach two weeks or even more.

In the study of the aerial parts we have found that depending on the heating of air and soil in the greenhouse, the growth of the shoots starts much earlier than recorded by different researchers in natural conditions. However, steady temperatures decline in the night leads to delayed development of plants.

The air temperature in the greenhouse is characterized by daily and annual fluctuations. The average daily temperatures during the warm period of the year mainly changes in the range of 20-24°C in the tropical zone and 20-22°C in the subtropical zone. Short-term minimum temperature for the entire observation period was up to 4°C and the maximum was 40 - 45°C. The highest temperature was in July, and the temperature is below 10°C were recorded in December and January. In general, a fluctuation in the average monthly temperature during the year ranges from 10°C to 24°C. The temperature during the day (from 7 to 16 h) was higher and in the night hours (from 16 to 7 h) was always lower: in winter at 1.5 - 4.0 °C, while in summer of 6.0 - 8.0 ° C. Biological, biochemical and physiological processes in plants subject to the Vant-Goff temperature coefficient. They double their intensity when the temperature increases by 10°C. Citrus plants are a typical poikilothermic organisms, i.e. their body temperature is completely determined by the ambient temperature. The heat distribution throughout the greenhouse should be uniform. Do not adhere to the allowable or maximum temperatures. The average temperature should be maintained within the statutory regime.

In greenhouses it depends on the time of year, the phase of biological development of plants are taken into account – the period of rapid or slow growth, a period of rest. The average temperature in winter of the subtropical zone is maintained in the range of 8°-14°S, the tropical zone of 16°-22°C, in summer - 20°-22°C and 22°-26°C. Phenological phases of rutaceae family in a greenhouse conditioned varietal and species composition. From early periods to the later types of citrus are placed in the following order: lemon, Mandarin, orange, grapefruit, kumquat, Poncirus.

In the varietal composition of lemons growing season starts early modern Georgian, followed by Meyer and Ponderosa. Duration of flowering in the studied conditions is for varieties of lemon from 29 (modern Georgian) to 36 (of Ponderosa) days, in orange – 34 days, kumquat – 20 days, which is significantly higher than in the wild – from 11 to 22 days. Tangerine, grapefruit and Poncirus in our conditions did not create generative buds, which testify to the insufficient level of introduction.

The timing of maturation of citrus fruit is divided into early, middle and late. Special attention is paid to the first and the last to extend the period of delivery of the fruit to the final consumer.

The maturation of citrus, unlike other plants, is not pronounced and the fruit can stay on the tree after ripening, however, with this gradually reduced their quality.

Citrus plants under the influence of low temperature pass into a state of forced peace. The longer the period of a forced peace state, the better adaptation of plants to low temperatures. Varieties of lemons are not fundamentally different from each other for the duration of the rest and it takes 91 days. The longest it was the Mandarin and grapefruit state – for 124 days and the shortest one - in orange – 78 days.

Thus, phenological phases of development of citrus in the greenhouse are longer than natural. Total vegetation period in different taxa is: lemon varieties – from 268 days in Ponderosa to 286 in Meyer, orange – 285 days, Mandarin – 259, grapefruit – 252, kumquat – 287 and Poncirus – 226 days.

As a result of the experiment the influence of temperature regime on the growth processes of citrus, such as the distribution of heat throughout the greenhouse evenly, is investigated. It is shown that one should maintain an average temperature within the statutory regime. The average temperature in winter of the subtropical zone is maintained in the range of 8°-14°S, the tropical zone of 16°-22°C, in summer - 20°-22°C and 22°-26°C. The main terms of passing phenological phases rue are determined in a greenhouse. They are entirely dependent on the species and varietal composition of citrus. From the early timing of the onset of the growing season to late in the species of citrus are in the following order: orange, lemon, Mandarin, grapefruit, Poncirus, kumquat.

In citrus varietal composition of the average for 2015 - 2016 rr. earlier the growing season begins among lemon varieties of Ponderosa (08.01), from oranges – the variety is pear-shaped Bead (05.02), mandarins (01.02), grapefruits (09.02). Citrus fruits are characterized by a long vegetation period, which is for lemon varieties 264 - 287 days, orange 281 – 289 days, Mandarin 242 – 270 days, grapefruit cincan242 days.

In the study of the aerial parts we have found that depending on the heating of air and soil in the greenhouse, the growth of the shoots starts much earlier than recorded by different researchers in natural conditions, however, a steady decline in temperatures in the night leads to delayed development of plants.