Production characteristics of Papaver somniferum L. cultivars of different origin and vegetation cycles
Author: J. BERNÀTH, P. TETENYI
Pages: 113 to 127
Creation Date: 1982/01/01
Production characteristics of Papaver somniferum L. cultivars of different origin and vegetation cyclesJ. BERNÀTH
Research Institute for Medicinal Plants, Budakalász, Hungary
Poppy cultivars of different origin were investigated in long-term experiments during the period 1976 - 1980. The production ability of plants was established with both spring and autumn sowing, using different plant spacing (20 cm x 20 cm and 50 cm x 20 cm). All important poppy-growing areas within northern and southern Europe were represented by the cultivars brought under investigation ("P-360", "Ankara", "Botosani", "Kompolti-M", "Kék Duna", "Modran", "KM-Ihar" and "Reading").
The extension of the vegetation cycle by autumn sowing and wintering had a generally favourable effect on dry matter and alkaloid production, resulting in a fivefold increase in production. In spite of high production ability, the wintering of the cold-sensitive cultivars, known as spring types, was uncertain. The shortening of the vegetation cycle (spring sowing) seemed to be unfavourable for the production of both spring and autumn cultivars. However, that disadvantage was compensated to some extent by spring cultivars having relatively lower sensitivity and higher alkaloid production levels.
The weight of individual plants was much higher when cultivated in large areas. However, a higher yield could be obtained with 20 cm x 20 cm spacing because more plants could be harvested per square metre. On the basis of production analyses, a negative correlation was established between the total capsule mass (i.e. capsule plus seed) and the ratio of the drug-forming part. In the case of alkaloid production, a positive correlation was established between the accumulation of codeine and the intensification of over-all alkaloid formation.
On the basis of modern biological sicence a poppy-growing system, which provided for cultivation of a large number of crops, was developed in Hungary. However, the average yield and alkaloid content of the poppy varied considerably within this system.
In order to protect the crops and ensure consistency in yields, the reason for these fluctuations as well as the environmental-genetic interaction had to be analysed. Until the mid-1970s, the reasons for these quantitative and qualitative differences were unknown.
It was difficult to identify and separate factors such as geographical location (Lee Chang Ki and Hyung Kook Kim, 1970), climate (Tétényi, 1970, Hotyn and Novikova, 1968), or soil and nutrient supply (Kusevíc, 1960), which might be responsible for the differences in production.
The use of the phytotron by United States scientists in such investigations (Tookey and others, 1976) led to considerable progress and the results enabled the authors to carry out a more comprehensive analysis than would have been possible with field results alone (Bernáth and Tétényi, 1979, 1980, 1981).
The aim of this research was to analyse the influence of spring and autumn sowing on production, and to compare cultivars of different origin and chemical content. The experiment included the following eight poppy cultivars:
"P-360'' (Bulgarian autumn standard under Hungarian conditions)
"Kék Duna'' (Hungarian, the spring standard variety of Hungary)
According to their geographic origin, the cultivars represented regions between the town of Reading in the United Kingdom of Great Britain and Northern Ireland and the city of Ankara in Turkey. While two of the cultivars, "Ankara" and "P-360", were autumn-sown types, Reading was of uncertain variety ; five cultivars were spring-sown varieties only.
All plant materials were tested by sowing both in spring and in autumn. The experiment started with spring sowing in 1976 and was completed in the spring of 1980. The following time-related variables were investigated:
Date of spring sowing
Date of autumn sowing
|1976||18 March||14 September|
|1977||8 March||26 September|
|1978||13 March||15 September|
|1979||12 March||18 September|
The spring sowing supplied data for all cultivars each year. Wintering of the spring cultivars was successful during one year only, 1979 - 1980. Autumn-sown cultivars were damaged by frost during the winter of 1978 - 1979; the temperature in January 1979 reached lows of - 15°C and - 20°C, without snow, and averaged - 2.8°C. Three autumn and five spring cycles were available for comparison. In the case of all cultivars, 50 cm x 20 cm and 20 cm x 20 cm row spaces were applied, in four replications. The area of each plot was 20 m2.
Growth and development of the plants Were registered continuously by morpho-phenological investigations. The plants were processed after full ripening of the poppy capsules and their dry matter and morphinane alkaloid production were evaluated. Alkaloid content and composition were determined by thin-layer chromatography (Dános, 1968) and checked with Hewlett-Packard High Performance Liquid Chromatography (HPLC).
Meteorological data for the period are shown in table 1.
When cultivars regarded as standard under Hungarian conditions were compared, using their own optimal sowing conditions, the effect of large spacing on the growth of capsules was obvious (table 2). The repeated autumn sowing of the standard cultivar "P-360" produced a significantly higher yield of capsules per plant during a three-year period. A similar tendency was also observed in the spring standard "Kék Duna". The favourable effect of the greater cultivation area was partly because of the increase in the number of capsules per plant, as well as the increase in the average mass of the capsule. In contrast to the influence of wide spacing on the growth of capsules, the total amount of production per unit area was greater when plants were more tightly spaced because of the increased number of individual plants. The advantage of autumn sowing proved to be characteristic. Since the higher yields per unit area appeared in more closely spaced plants, further comparisons were made under those conditions.
Extension of the vegetation time
In general, autumn sowing and wintering of the cultivars had a favourable effect on yield, as shown in the 1979 - 1980 data, when all cultivars wintered successfully because of the mild weather. Spring cultivars also responded favourably to the longer vegetation phase, with a yield of from 70 to 300 per cent higher than regular spring production (see table 3). The advantage of wintering was first apparent in the increase in the number of secondary capsules or off-shoots. Even the cultivar "Reading'', normally bearing only one capsule, produced two capsules under these conditions, which was equivalent to the "Kék Duna'' under spring sowing conditions. No response was observed in the cultivar "Botosani''. Moreover, the number of capsules per plant decreased, but in cultivars "Modran'' and "KM-Ihar'', the number of capsules doubled.
The greater mass produced in one poppy capsule was another benefit of wintering. The mean mass of one capsule of the autumn standard cultivar (1 .91 g) was significantly exceeded by both "Modran'' and "Reading''. The Hungarian spring standard was equal to the cultivar "Ankara'', and the "KM-Ihar" equalled the autumn standard. Among the spring cultivars, "Botosani'' was the least successful, its response to the longer cultivation period was low.
Following autumn sowing, the mass of secondary capsules became dominant in production as a result of the increased number of off-shoots and mean capsule mass (see figure 1). This response was shown particularly well in "Reading'' and the spring cultivars. In the case of "Reading'', wintering was a pre-condition for the appearance of side-capsule production, whereas in the spring cultivars the 1 : 1 ratio of primary-secondary capsules increased to 1 : 2 - 1 : 3 in the case of autumn sowing.
Spring sowing caused decreased yields in all cultivars. Table 3 shows a significant short-fall of autumn cultivars in comparison with the spring standard, which was partly a result of the decreased number of capsules per plant and partly because of the decreased average capsule mass. Among the spring cultivars, "Reading'' lagged significantly behind the standard. However, this may be explained by a substantial decrease in the number of capsules. The decrease was noted in other spring cultivars in comparison to their winter production, with the exception of "Botosani'' which, as mentioned earlier, responded with an increase of 21 per cent. This proved a low sensitivity to the vegetation type of that cultivar. The high individual capsule mass of "Reading'' was excellent among those grown during the spring cycles.
A comparison of the five-year production data of spring and autumn cultivars showed that the proportion of the drug-forming part varied between capsules (see table 4). Benefits of the longer cultivation period were also obvious from the five-year production data. However, the capsule and seed portion in total capsule mass varied characteristically in this accumulation. In the case of autumn cultivars, the coefficient of correlation between total capsule weight (capsule plus seed) and utilized capsule drug amounted to about - 0.8. In the case of spring varieties this negative dependence was moderately high, while "Modran'' and "KM-Ihar'' hardly responded at all. This also indicated the higher ratio of seeds out of the total production in the majority of cultivars supporting the experimental observations related to autumn cultivars.
Thus, the yield was essentially determined by the length of the vegetation period. However, this was influenced by the different growth and off-shoots on the cultivars. Under local conditions, the vegetative phase of autumn cultivars became shorter in the case of spring sowing, the plants bursting quickly into bloom (see figure 2). The supply of capsules was determined by a smaller vegetative mass, hindering the "mass-gaining'' of the crop in reaching the usual autumn size and mass. The successful wintering of spring cultivars, once in five years, lengthened the vegetative phase and although blossoming took place earlier than with spring sowing, production of poppy capsules was higher and the growing capsules were better supplied with a greater vegetative mass. The phase-indifferent "Botosani'' was an exception.
Under Hungarian conditions, the length of the vegetative phase was mainly affected by temperature, although the day-length in the response of cultivars was also an important factor. It was observed that autumn-sown cultivars of Indian origin, which perished as a result of frost in Hungary, blossomed after a short vegetative phase when sown in spring and produced capsules which were like dwarf plants. This response was brought about by longer day-time in the case of these autumn cultivars, controlled by the phytochrom system of the plant, and was a consequence of their adaptation to Indian weather conditions.
Local spring cultivars, if sown in autumn under Indian weather conditions, were unable to thrive under a longer vegetation period. Their response was the same as that of Indian cultivars in Hungary : they blossomed after a short vegetation period, producing dwarf plants and capsules. The reason for this phenomenon was the short day-time impulse along with the higher temperature of India during the vegetation period.
Thus, the cultivars grown and tested by the authors may be classified into several groups according to their mode of response :
Cultivars of Indian origin sensitive to the length of day-light ;
Cultivar "Botosani" , indifferent to the length of day-light ;
Other cultivars which needed a long day-period.
Within this latter group the autumn cultivars required a long vegetativ phase, while the spring types gave good yields after a short vegetative phase. The cultivar "Reading" was in a mid-position, requiring a longer vegetative period. However, it was not cold-resistant under Hungarian climatic conditions. From this diversity, the plasticity and ecological adaptability of the poppy species was obvious. The thousand-year old breeding and acclimatization involving hundreds of generations had resulted in individual evolution.
The standard cultivars showed a characteristic alkaloid accumulation in a condition-system considered as optimal thereto ("P-360" in autumn sowing, "Kék Duna" in spring sowing), depending upon annual climatic conditions. The morphinane level calculated on dry matter (mg/g) was significantly higher in the spring standard in spite of differences in climatic conditions between years (e.g. temperature, humidity etc.) (see table 5). This advantage of the spring standard was obvious in all three vegetation cycles. However, the influence of the cultivated areas on the alkaloid level could not be proved.
In the production of alkaloids the role of the cultivated area was significant. On the one hand, the greater space appreciably increased production per plant due to the higher capsule number and capsule weight. On the other hand, the favourable effect of more space did not occur when alkaloid production was related to unit area. A larger plant number of 20 cm x 20 cm area both in the autumn and spring cultivars accumulated more morphine (from 20 to 100 percent), per square metre. The various cultivars were compared in this area, taking into consideration the data of 1979 - 1980 for supplying a complete vegetation cycle (see table 6).
Lengthening of the cultivation period
Lengthening of the cultivation period reduced the alkaloid level of the "Kompolti M'' and "Kék Duna'' cultivars, caused no change in "KM-Ihar'' and "Modran'', and significantly increased the alkaloid level of "Reading'' and "Botosani''. The longer cultivation time, combined with climatic conditions, also produced the alkaloids codeine and thebaine. Nevertheless, the benefit of longer cultivation time manifested itself definitively in the yield per plant and per unit area in the case of the spring cultivars. The surplus was 100 to 500 per cent, as compared with values obtained in the spring cycle. The potentially higher productivity of spring cultivars was clearly shown by the fact that, in the case of autumn sowing, the morphinane production of all cultivars was higher than that of the standard "P-360'' sown in autumn.
Shortening of the cultivation period
The spring cycle was definitely unfavourable for both the morphinane level and the morphinane production. The morphine content of the autumn standard was only 1.8 mg/m which resulted, along with the reduced production of dry matter, in a morphine yield of only 2.7 mg per plant.
This was about one quarter of the production of the spring cultivars. In addition to the autumn cultivars, "Reading'' and "Botosani'' were of higher sensitivity, decreasing their production in the spring cycle as compared to autumn sowing.
On the basis of data given in table 7 it was obvious that the alkaloid content depended considerably on the annual climatic conditions. The difference between the alkaloid levels of favourable (1976) and unfavourable (1978) years could be as high as five- or sixfold. The cultivars "Ankara" and "Reading" were most sensitive to changes in external conditions, while the "Kompolti M'', "Kék Duna'', "KM-lhar'' and "Modran'' cultivars were relatively balanced. In accordance with investigations carried out under controlled conditions (Bernáth and Tétényi, 1979, 1980, 1981), the change of total morphinane content implied the modification of the proportion of inner alkaloid components. The increasing alkaloid accumulation was characterized by the enrichment in codeine and, to a lesser extent, in thebaine. This was supported by the calculated values for total morphinane and codeine contents. All cultivars investigated showed positive relation- ships in this respect. In only two cases could the correlation be considered as moderately strong ("Reading'') or low ("Modran''). The weaker relation shown by "Reading'' could be attributed to the codeine chemical content forming codeine under relatively unfavourable conditions as well.
The alkaloid production could be influenced under Hungarian conditions by the choice of cultivars, the type of vegetation cycle and by determining the most favourable spacing (see table 8).
Biologically, the longer cultivation period had a favourable effect on the autumn cultivars and this was manifested in an increase in their production of dry matter and active substance. The disadvantages were expressed both by the lower morphinane level and by the increased seed proportion. Spring cultivars gave potentially high yields. However, cultivation was assured only in the spring vegetation cycle. The alkaloid yield was insignificantly lower in the spring cycle, since the reduced dry substance yield of a shorter vegetation period was compensated by the higher alkaloid level.
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