In order to obtain high yields and good quality of products, as well as to preserve natural resources and biodiversity, the production of medicinal plants is becoming more popular. It is known that it can be raised either by direct seeding or by transplantation from the nursery plant. A two-year research study (1998 and 1999) included a number of variants for nursery plant production of eight medicinal plant species with relatively tiny seed, which rarely propagate after direct seeding. Following species were investigated: Melissa officinalis, Angelica archangelica, Lavandula vera, Valeriana officinalis, Thymus vulgaris, Ehinacea and Klamath weed (Hypericum perforatum).

The seeding was carried out in eight variants. First four variants were covered by peat, and the remaining four by earth. The seedbeds were regularly watered, twice a day with 5mm water sediment.

The best results of all (eight) investigated plant species in both investigation years were obtained in the variant four. That seed was sown randomly and covered with peat. The same seed was previously cooled for 72 hours on 4°C. The plants of this variant emerged (appeared) first and their emergency rate (rate of appearance) was the highest.

The poorest results of all eight plant species in both investigation years were obtained in variant five. Uncooled seed was sown in rows and covered with earth. This variant needed the longest time to emerge and showed the lowest percentage of seedlings.

Key words: Nursery plant, seeding, cool seedbeds, emerging.

The natural resources of the medicinal plants are decreasing rapidly, especially over the last several decades. Excessive, and particularly nonprofessional exploitation accelerated even more this decrease. In order to protect and preserve the biodiversity, as well as to achieve high yields and good and standard quality of products, the production of medicinal plants is increasing. The incidence of increased production of medicinal plants is typical for certain more developed West European countries but also for ours.

Like certain plow and vegetable cultures, medicinal plants can be raised by direct seeding on the production lot, or by transplantation from the nursery plant. As a rule, plants with larger seed are produced by direct seeding, while plants with smaller seeds by transplantation from the nursery plants.

In this research study, eight variants of the nursery plant production and eight medicinal plant species with relatively small seeds, therefore rarely produced by direct seeding, were investigated. All of them endure summer conditions of nursery plant productions, therefore the possibility of the production in cooled seedbeds was also investigated. The transplantation of the nursery plants to the permanent spot in all eight investigated species is, as a rule, conducted during the fall. Exceptionally, should the seeding during the fall be unsuccessful, for any reason, the transplantation can be carried out in the spring, but with poorer results and lower yields.

The objective of the two-year researches was to obtain the most favorable variant of the medicinal nursery plant production in cooled seedbeds.

In these researches the seed material for eight plant species produced in the Institute for medicinal plants, Pančevo, was used: Melissa officinalis, Angelica archangelica, lavender (Lavandula officianlis L.), valerian (Valeriana officinalis L.), thyme (Thymus vulgaris L.), marsh mallow (Althaea officinalis L.), echinacea (Ehinacea purpurea) and St. John's wort (Hypericum perforatum L.). Natural seed material was processed up to the standard, germination checked (Jevđović and Maletić, 1998). For further investigations the seed with 97% of germination rate was used.

The seeding was carried out in cooled seedbeds, depth of 0.5cm (Jevđović et al., 2000). 600 seeds of each species (eight) were sown per 1m² of seedbeds. The date of seeding: July 20, 1998 and July 22, 1999. The seeding was carried out in eight variants (same method applied by Jevđović et al., 2000):

I variant - uncooled seed sown in rows, covered with peat;
II variant - broad casting of uncooled seed, covered with peat;
III variant - cooled seed sown in rows (cooled for 72 hours on temperature of 4°C), covered with peat;
IV variant - broad casting of cooled seed (cooled for 72 hours on temperature of 4°C), covered with peat;
V variant - uncooled seed sown in rows, covered with earth;
VI variant - broad casting of uncooled seed, covered with earth;
VII variant - cooled seed sown in rows (cooled for 72 hours on temperature of 4°C), covered with earth, and
VIII variant - broad casting of cooled seed (cooled for 72 hours on temperature of 4°C), covered with earth.

Seedbeds were watered regularly twice a day, in the morning and evening, with 5mm water sediment (Jevđović, 2000). The mechanical weed extermination was carried out regularly. The control of the plant emergency and counting of the emerged plants was carried out each three days, since the day when the first plant emerged (July 26, 1998 and July 27, 1999).

The relative structure of the emerging of certain variants of each plant species, in both investigation years, was determined by statistical analysis of obtained data (Hadživuković, 1991).

The percentage of emerged plants according to variants, in both investigation years, is presented in Table 1.

General impression regarding all plant species (based on Table 1.) is that there was greater number of emerged plants in 1999 compared to previous year 1998. This is primarily the result of greater quantities of water sediment during the emerging period of nursery plants (in 1998 - 94 mm, in 1999 - 350 mm), as well as higher average-monthly temperatures in the same period, in year 1998 21.9°C, in year 1999 22.4°C. Also, the emerging dynamics according to certain seeding variants of each plant species was identical in both investigation years, with the exception of marsh mallow in the fifth seeding variant (in year 1998 the same variant gave the nursery plant material three days later compared to the next year).

The investigated plant species had different structure and emerging times in different seeding variants.

Melissa officinalis shows the identical emerging dynamics in regard to the investigation years, and similar emerging structure in regard to certain seeding variants within investigation years. The fourth seeding variant, broad casting of cooled seed covered with peat, in both investigation years, showed the greatest number of emerged plants (571 in 1998, and 580 in 1999). Since it is known that the seed used in this investigation had germination rate of 97%, and that the maximum number of new plants was 582, obviously the fourth seeding variant gave extremely good results, exceptionally great number of new plants. Besides, this seeding variant provided the quickest (earliest) emerging time. Broad casting of the cooled seed covered with earth (VIII variant) provided the similar emerging period as in the previous, IV seeding variant, however, smaller number of emerged plants (502 in 1998 and 510 in 1999). Remaining seeding variants expressed later time of plant emerging (three days), as well as less emerged plants (from 402 to 501 in 1998, and 364 to 503 in 1999). Seeding in rows of uncooled seed, covered with soil, V seeding variant, in both investigation years, showed the lowest emergency percentage (67% in 1998 and 61% in 1999). Obviously, the most favorable procedure/method for the plant species Melissa officinalis is broad casting of cooled seed, primarily covered with peat, followed by soil.

Plant species Angelica archangelica has the same emerging dynamics of certain seeding variants, in both investigation years, and similar emerging structure of seeding variants according of investigation years. In relation to other investigated plant species the lowest emergency percentage in all variants in both investigation years was observed in case Angelica archangelica. The quickest emerging and the greatest number of emerged nursery plants was obtained from the broad casting of cooled seed, covered with peat - IV seeding variant (302 plants or 50% of sown seed in 1998, and 311 plants or 52% in 1999). In regard to the emerging time and number of emerged plants, follows the VIII variant - broad casting of the cooled seed, covered with earth (264 in 1998 and 286 in 1999), than the VII variant - cooled seed sown in rows, covered with earth (34% of sown seed in 1998 and 36% in 1999). The last seed to emerge was the seed sown by the first, second, fifth and sixth seeding variant. So, for this plant species, the most favourable method was broad casting of cooled seed covered with peat, since it provided the earliest and the largest emerging of nursery material (14% more emerged plants compared to the following variant, broad casting of cooled seed, covered with earth - VIII variant).

Lavender (Lavandula vera) shows identical emerging dynamics of plants in all seeding variants in both investigation years, as well as almost the same emerging structure of the seeding variants in both investigation years. Broad casting of the cooled seed, covered with peat - IV seeding variant expressed the quickest (earliest) emerging as well as the greatest number of emerged plants (423 in 1998 and 425 in 1999). The difference between two investigation years was established only in regard to the time of emerging of plants: in this seeding variant, in 1999, the emerging of plants started three days later than in 1998. The broad casting of uncooled seed, covered with peat (second seeding variant) provided in sequence the emerging of plants as follows, providing 14% less nursery plants in comparison to the best, fourth seeding variant (371 plants in 1998 and 376 in 1999), followed by V and VII seeding variant. The poorest results, the last emerging of plants and the least emerged nursery plants of lavander was obtained by the first seeding variant, uncooled seed sown in rows, covered with peat (54% of emerged seed in 1998 and 55% in 1999), and the sixth seeding variant, broad casting of uncooled seed, covered with earth (57% in 1998 and 58% in 1999).

Valerian (Valeriana officinalis) as a plant species expressed the same emerging dynamics in all variants in both investigation years, as well as the same emerging structure of certain seeding variants within the same investigation year. Broad casting of cooled seed, covered with peat, gave the quickest (earliest) emerging of plants as well as the greatest number of plants. In this seeding variant, 95% of sown seed emerged, that is 571 plants in 1998, and 574 in 1999. Remaining seeding variants showed later emerging of plants with lower percentage of emerged plants. The number of emerged plants decreased with the longer period of emerging. The seeding variant V (uncooled seed sown in rows, covered with earth), VI (broad casting of uncooled seed, covered with earth) and VII (cooled seed sown in rows, covered with earth) had the latest emerging time, in average 64%, 64% and 65%, respectively. It is apparent that all seeding variants in which the seed was covered with earth, the emerging time was prolonged which reproduces (as a result has) less emerged plants.

Thyme (Thymus vulgaris) has the same emerging time of all seeding variants in both investigation years, and almost the same total number of emerged plants per year. The quickest (earliest) emerging time and the greatest number of emerged plants were recorded in the seeding variant IV, that is broad casting of cooled seed covered with peat (530 plants in 1998, and 528 in 1999), followed by emerging of plants sown by broad casting of uncooled seed and covered with peat - seeding variant II (74% of emerged seed in both investigation years), and the seeding variant III, cooled seed sown in rows and covered with peat (84% in 1998 and 85% in 1999). These two seeding varianrs induced three days late emerging of plants compared to the IV seeding variant, which is the most favourable variant. Uncooled seed sown in rows and covered with earth (V seeding variant) provided the least emerged plants (408 in 1998 and 411 in 1999), as well as the latest emerging of plants, therefore in regard to the production of nursery thyme plants recorded the poorest results.

All seeding variants in the production of marsh mallow (Althaea officinalis) showed in the most favourable (earliest) period simultaneous emerging of plants in both investigation years. Differences among seeding variants are present only in regard to the total number of emerged plants. So, the IV seeding variant provided the most of young plants (575 in 1998 and 579 in 1999), followed by seeding variant VIII (570 in 1998 and 572 in 1999), than seeding variant III, and so on. The lowest percentage of emerged plants was established in the seeding variant V, uncooled seed sown in rows and covered with earth, only 68% per investigation year.

Echinacea (Ehinacea purpurea) has the same emerging dynamics of the nursery plants of all seeding variants. The quickest (earliest) plant emerging was established in the method of broad casting of the cooled seed, covered by peat. In the first investigation year in this seeding variant, there were 551 emerged plants or 92% of sown seed, and in 1999 567 plants or 94.5%. The latest emerging time influenced less emerged nursery plants, which was observed in 1998 in the seeding variant V, uncooled seed sown in rows and covered with earth - 67%, seeding variant VI, broad casting of uncooled seed covered with earth - 68%, and in 1999, only in the seeding variant V, uncooled seed sown in rows and covered with earth - 67%. Remaining seeding variants were three days late in regard to the emerging compared with the best seeding variant - IV, therefore the number of emerged plants was slightly lower compared to the seeding variant VI. The eight, followed by the third seeding variant, gave also high percentage of emerged plants (92% and 90%).

St. John's wort (Hypericum perforatum), in relation to previous plant species, showed relatively the latest emerging time in all eight variants which was reflected negatively on the quantity of the emerged plants. The cooled seed sown in rows, covered with peat (seeding variant III) and the uncooled seed sown in rows, covered with earth (seeding variant VII) in both analysed years gave the quickest (earliest) emerging of plants (August 4^th and 5^th). It is obvious that for this plant species the seeding of cooled seed in rows is most adequate regardless of the cover (peat and earth). The third seeding variant gave 465 and 479 plants respectively in 1998 and 1999, and the VII seeding variant 461 plants in 1998 and 454 in 1999. The latest emerging of the nursery Klamath weed plants was observed in I, II, V and VI seeding variant which reflected drastically on the quantity of emerging plants. In these seeding variants only 35 to 41% of the sown material emerged.

The investigation of the seeding method as a factor of the timely production of the medicinal nursery plants gave following results:

1. The favorable climatic conditions in 1999 induced more emerged plants in all seeding variants;

2. The emerging dynamics of seeding variants within a single plant species per investigation year recorded the same trend;

3. Plant species showed a different emerging structure in certain seeding variants;

4. The broad casting of cooled seed (cooled for 72 hours on temperature of 4°C), covered with peat - IV seeding variant, expressed in all plant species (except Klamath weed) the quickest (earliest ) emerging of nursery plants and the most emerged plants;

5. The broad casting of cooled seed, covered with earth, also showed exceptional quantity of emerged plants in all plant species (except in case of Klamath weed), but often with three days delay in emerging in comparison with the most favorable IV seeding variant;

6. The uncooled seed sown in rows, covered with earth (V seeding variant) expressed in all plant species (except lavender) the latest and the poorest results in regard to the quantity;

7. The late emerging induced less emerged plants of the nursery material in all plant species.

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4. Jevđović R. (in press): Vreme setve faktor proizvodnje kvalitetnog rasada belog sleza.