A Preliminary Investigation on Possible Role of Allelopathy in Saffron (Crocus sativus L.)

M. Hosseini S.J.H. Rizvi Khorasan Research Center for Technology Development Professor of Plant Physiology P.O. Box 91735-139 Rajendra Agricultural Univ. Mashhad India. Iran.

Keywords: autotoxicity, wheat germination

Abstract A preliminary experiment was conducted on possible role of allelopathy in saffron. Seven treatments composing of soil and corm extracts of saffron were applied on seed germination of wheat (cv. Omid). The statistical method used for data analysis was carried out on the basis of Completely Randomized Design. The results showed that effect of substances present in saffron corms was evident on percent and rate of germination, dry weight of radicle and plumule of wheat seeds. Characters under investigation were adversely affected by extracts of old (E) and new (F) corms of saffron farms. There was a considerable loss compared to treatments: A, B, C, D, and G. It appeared that substances extracted from saffron corms showed autotoxicity effects reducing saffron yield after several years. More research is yet required to determine these substances and find possible elimination ways from saffron farms with biological treatments instead of displacing farms.

INTRODUCTION Saffron (Crocus sativus L.) is one of the most important crops in southern and central Khorasan. This crop has a considerable role in the socio-economic situation of people living in this area. Currently, saffron is cultivated in more than 20000 ha and in more than 15 cities of Khorasan province. Saffron cultivators experience yield reduction in their farms and they displace the farms after eight years. The reasons are not fully understood yet. Plants compete for moisture, light and nutrients. Part of this competition is chemical interaction (allelopathy) that in many cases are resulted from secondary substances. These chemicals are produced in different parts of plants. Allelopathy affects plant population and has been studied extensively (Chase et al., 1991; Rice, 1974; Waler, 1989). Allelopathy has an important role in growth, development and evoluation of plants (Hedin, 1990; Sing et al., 1992). Conventional method of allelopathy studies includes evaluation of extracts of embryos, roots and stems of growing plants (Athanassova et al., 1981; Greca et al., 1990; Roussev, 1974). Aqeous extract of Artemisia sp. has inhibitory effects on germination and elongation of recipient plants (Kil and Yun, 1992). Acid ferulic prevents from growth of leaves and reduces water consumption in tomato and cucumber (Hollapa and Blum, 1991). Purpose of this experiment was to determine probable presence of allelopathic chemicals in saffron corms.

MATERIALS AND METHODS In order to study saffron allelopathy, samples were collected from saffron corms and soils. Treatments were: soil of old farm (A), soil of old farm from where saffrons were selfthinned (B), soil of new farm (C), soil of a farm that saffron had not been cultivated in was used as control 1 (D), corm of old farm (E), corm of new farm (F), distilled water as control 2 (G). Samples were collected in autumn 1998 from two year old saffron farm (new one) and from eight year old saffron farm (old one) located at the experimental station of saffron and medicinal plants in Khezri, Ghaen. Samples of saffron corms and soils were collected from depth of 25 cm from soil surface. They were sent immediately, frozen and kept at temperature -40 °C before conducting the experiment. Samples were kept in the lab. temperature at least for two hours. Soil samples each one was mixed completely and 100 g soil was mixed into the beaker with 500 ml distilled water. Two collected corm samples, at first, separately were washed with water and then with distilled water. After this stage, each corm sample was kept in 80% ethyl alcohol for one minute. 100 g corms was transported into a grinder and crushed with a little distilled water (Rizvi and Commun., 1997). It was poured into a beaker with 500 ml distilled water. Since then, following the experiments for soil and corm samples were similar. Samples were shook for at least 18 hours with a shaker in 30 °C. Then, solutions were centrifuged with 4000 rpm. Solid phase was eliminated and the rest was passed from a membrane filter for decontamination of the microbes and the samples were transferred into the refrigerator with 5 °C. Samples were kept in the lab. temperature for a while before operation. In this stage, bioassay test was conducted on wheat seeds cv. Omid. Plates were sterilized in 150 °C and then the seeds were disinfected with 50 % Benomyl fungicide. 15 cm plates were used with 50 seeds in each one. 18 ml solution was added to each one. Each treatment with 4 replications was established. Wheat seed germination was tested in the darkness in 15 °C in the germinator. Germination (length of radicle as much as half the seed length) was measured for 5 days. Rate of germination was calculated with the following equation (MaGuire, 1962). M R.G.= ∑ i D In which M is number of germination till i th day, and D is number of days spent from the beginning of the test. Four wheat seeds were selected in each plate with four replications for measurement of radicle and plumule dry weights. On the basis of growth, in the 5th day plumules and radicles of the four seeds were put in an envelope and were kept in an oven with 65 °C for 48 hours. Thus, their dry weights were measured. Results were analysed statistically as C.R.D. (P<0.05), and means comparison with Duncan’s multiple range test.

RESULTS AND DISCUSSION As allelopathic chemicals have adverse effects on different stages of growth and development in plants, this property is shown very well in figures 1 and 2. As in the figure 1(a), percent of germination in wheat is significantly affected by corm extracts. Treatments E and F are corms of old and new farms, respectively that have significantly reduced percent of wheat germination. There were not any significant reductions among other treatments about this character. This situation is the same for rate of germination in wheat (Fig. 1b). It was shown that chemicals present in saffron corms have strong preventive effects and they must be determined with advanced researches. Sampling was in autumn and it seems that excreted chemicals from corms into the soil were not so much that have significant effects on wheat seed germination. If sampling was done in other months, maybe, It would have significant effects. Figure 2 (a) shows dry weight of wheat radicle affected by corm extract of old farm (E) and showed significant difference compared with control 1 (D) and control 2 (G). Dry weight of radicle in four treatments related to soil and corm samples of new farm was affected by allelopathy but this effect was less than treatment related to corm of old farm. These chemicals also had negative effects on dry weight of wheat plumule (figure2b). Corm extracts of old farm (E) and new farm (F) reduced significantly dry weight of wheat plumule. Aqeous extract of leaves and roots of Chenopodium murale also prevented from germination and growth of wheat and barley seedlings under laboratory conditions (Qasem, 1993). Perez et al. (1991) reported about effects of excreted chemicals from wild oat roots on spring wheat. Ben-hammonda et al. (2001) have reported that aqeous extract of barley reduces radicle and plumule growth of durum and bread wheat. Results show that there are allelopathic chemicals in saffron corms. In order to determine these chemicals and their adverse effects on different stages of saffron growth and development as autotoxicity further researches are needed.

Literature Cited Athanassova, D.P., Roussev, G. and Konstantinov, K. 1981. Isolation of specific factors from embryos of Echinochola crusgalli L. Plant Physiology, Sofia 7: 78-85. Ben-Hammouda, M., Ghoral, H., Kremer, R.J. and Oueslati, O. 2001. Allelopathic effects of barely extracts on germination and seedlings growth of bread and durum wheats. Agronomie 21:65-71. Chase, W.R., Nair, M.G. and Putnam, A.R. 1991. 2, 2- Oxo- 1”azobenzene: Selective toxicity of rye (Secale cereale L.) allelochemicals to weed and crop species. J. Chemic. Ecol. 17:9-19. Greca, M.D., Mangoni, I., Molonaro, A., Monaco, P. and Previtera, L. 1990. (20S)-4- methylenecholes- 7- en- 3- ol an allelopathic sterol from Typha latifolia. Phytochemistry 29:1797-1798. Hedin, P.A. 1990. Bioregulator induced changes in allelochemicals and their effects on plant resistance to pests. Crit. Rev. Plant Sci. 9:371-379. Hollapa, L.D. and Blum, U. 1991. Effects of exogenousely applied ferulic acid, a potential allelopathic compound, on leaf growth, water utilization and endogenous abscisic acid levels of tomato, cucumber and bean. J. Chem. Ecol. 17: 865-886. Kil, B.S and Yun, K.W. 1992. Allelopathic effects of water extracts of Artemisia princes var. orientalis on selected plant species. J. Chem. Ecol. 18:39-51. MaGuire, J. D. 1962. Speed of germination, Aid in selection and evaluation for seedling emergence and vigor. Crop Sci. 2:176-177. Perez, F.J. and Ormeno- Nunez, J. 1991. Root exudates of wild oats: Allelopathic effects on spring wheat. Phytochemistry (United Kingdom). 30:2199-2202. Qasem, J.R. 1993. Allelopathic effect of nettle- leaved goose foot (Chenopodium murale) on wheat and barely. Dirasat (Jordan). V. 20B (D). p. 84-94. Rice, E.L. 1974. Allelopathy. New York. Academic Press. 353 pp. Roussev, G. 1974. Programme of embryonic development directed by ontogenines. Sofia: Science and Art. 298 PP. Singh, K., Shahi, A.K., Pal, S. and Balyan, S.S. 1992. Phytoallelopathic influence of Parthenium hystrophorus L. In: Proceedings of First National Symposium on Allelopathy in Agroecosystems (Agriculture and Forestry) (Eds., P. Tauro and S. S. Narwal), pp. 61-63. Hisar, India: Indian Society of Allelopathy. Waler, G.R. 1989. Biochemical frontiers of allelopathy. Biologia Plantarum 31:418-447. a) a 60 a a a 50 a

40

30

20

Percent germination of b 10 b

0 A B C D E F G

b) Treatments

16 a a a 14 a 12 a 10 8 6

Rate of germinationRate of 4 b 2 b 0 A B C D E F G

Treatments Fig. 1. Effects of different treatments of soils and corms of saffron on percent of germination (a) and rate of germination (b) in wheat seed. A: soil of old farm, B: soil of old farm from where saffron was selfthinned, C: soil of new farm, D: soil of no saffron cultivated (control 1), E: corm of old farm, F: corm of new farm, G: distilled water (control 2). (a)

a 0.025 a a 0.02 a a 0.015

0.01 b

Dry radicle weight of (gr) 0.005 b

0 A B C D E F G

Treatments (b)

0.045 a 0.04 a a 0.035 a a 0.03 0.025 0.02

0.015 b 0.01 b Dry plumule weight of (gr) 0.005 0 A B C D E F G

Treatments

Fig. 2. Effects of different treatments of soils and corms of saffron on dry weight of radicle (a) and dry weight of plumule (b) in wheat seed. A: soil of old farm, B: soil of old farm from where saffron was selfthinned, C: soil of new farm, D: soil of no saffron cultivated (control 1), E: corm of old farm, F: corm of new farm, G: distilled water (control 2).