Rezk, Malak R.

English

Rezk Malak R.

University of Szeged

Acta Biologica Szeged 13, (3—4), pp. 39—44 (1967) STUDIES ON THE LIGHT SENSITIVITY OF PLANTAGO MAJOR L. SEEDS II. THE EFFECT OF RED LIGHT ALONE AND MEDIATED BY CHEMICALS M A L A K R. REZK Institute for Plant Morphology and Systematic of the Attila József University, Szeged (Received December, 1967) Introduction In an earlier contribution ( R e z k , 1968), the effect of gibberellin, kinetin, and potassium nirate solutions on the germination in the dark of the light — sensitive seeds of Plantago major has been investigated. It has been shown in that part of the work that gibberellic acid only could promote the dark germination of those seeds, while the other two chemical substances could not. It is yet always convenient to think of promoting the germination of such light — sensitive seeds by exposing them to irradiation from red light sources for varying periods of time. This promoting effect of red light is reported to be reversible by a subsequent irradiation with far-red light (B o r t w i c k, et al., 1954; D o w n s , 1955; A l c o r n , et al., 1959; K a h n, 1960; í k u m a , et al., 1960; M o h r , et al., 1963; and M c D o n o u g h, 1965. . . ) . A combination of either kinetin or potassium nitrate solutions with red light was thought to promote the germination in the dark of those seeds. Such combinations were previously tried by many other authors. Thus, T o o l e et al. (1955) could promote the germination of different light-sensitive seeds (e.g. Lepilium densiflorum) using 0.2 % K N 0 3 solution only after irradiating them with red light. K h a n and T o 1-b e r t (1965) came to the conclusion that neither kinetin nor red light alone were able to reverse the inhibitory effect of coumarin and xan-thatin on seed germination, but only a combination of both treatments was able to reverse this inhibitory effect. Thus the effect of red light alone and in combination with either kinetin or potassium nitrate solutions on the dark germination of Plantago major seeds was experimented here. 40 Materials and Methods Irradiation with red light. Red light was provided f rom an iodine lamp ( T u n g s r a m , 1000 Watt), the light of which was passed through a glass basin containing water to avoid heating of the plant material and then through a metal interference filter ( C a r l Z e i s s , Jena) of 650 mu. The intensity of the delivered red light was measured by the technique of H o r v á t h and S z á s z (1965), and was found to be 3400 erg. cm3 sec. Fifty seeds were sown in each 9 cm. Petri-dish on two thicknesses of filter paper wetted with 6 ml. of distilled water. The seeds were imbibed in the dark for 24 hours before exposure to red light. Irradiation with red light was carried out for any of the following periods: 2, 5. 10, 20, 30, 40, 50, or 60 minutes. There were 200 seeds distributed in four Petri-dishes exposed to red light for each of these time intervals. Attention was paid that the temperature at the seed level did not change during irradiation. After irradiaton for the desired time period, the seeds were returned back to the dark inside an incubator in which the temperature was controlled at 2 5 + 1 C° C for 10 hours by day and at 20+ 1° C for 14 hours by night daily. A control of unirradiated seeds was simul-taneously run. After 15 days of dark incubation of the seeds were examined for the germination percentages. The experiment was repeated twice thus having eight dishes irradiated for each of the mentioned time intervals. For the sake of comparison, red light from fluorescent lamps of the intensity of 10,000 erg/cm-'/sec was used in irradiating 200 seeds for one hour after having been imbibed in distelled water for 24 hours. For the study of the ef fect of kinetin and potassium nitrate solutions mediated with red light, the seeds were imbibed in the test solution for 24 hours before being exposed to red light as described above. Five concentrations of kinetin solutions were prepared (1, 10, 20, 50, and 100 p.p.m.) in distilled water. Potassium nitrate solution used was a 0.2 % solution of the analytical reagent. For each treatment four hundred seeds were sown in the manner described before. The seeds were first imbibed in the test solution for 24 hours in the dark and then exposed to red light from either sources for one hour. After irradiation, the dishes were returned back to the dark incubator under the same conditions previously described. Results and Discussion From table I it is clear that neither red light from the interference filter nor from the flurescent lamps had any stimulatory effect on the germination in the dark of Plantago major seeds irrespective of the period of exposure. The response of the seeds to irradiation with red light from either sources is in contrast to that arrived at by many other authors working on many light-sensitive seeds. For example, A l c o r n et al., (1956) could stimulate the dark germination of the light sensitive Carnegiea gigantea seeds by irradiating them with red light for 30 minutes. T o o l e et al. (1955) gave a list of some light-sensitive seeds the dark germination of which was promoted by red light. Lettuce seeds (Lactuca sativa var. Grand Rapids) and several other varieties were the field of many researches due to their light-sensitivity and due to that they responded by germanition in the dark if they were irradiated with red light. The germination promotion was found to inciease with the 41 Table I. Effect of exposing the seeds of Plantago major to red light from two different sources for varying time periods, on their germination in the dark. Time of exposure Germination to Percentage red light (min.) 2 3.0 5 2.5 10 2.0 20 3.0 30 3.5 40 3.5 50 3.5 60 4.5 Red light from fluorescent lamps 4.0 for one hour Dark Control 4.0 increase of the exposure period to red light ( B o r t h w i c k et al., 1954; K a h n , 1960; I k u m a and T h i m a n n , 1960). More important in this respect is the reported similarity of the action of kinetin and red light as viewed by M i l l e r (1956 and 1958). The only difference in M i 11 e r ' s results was that far-red light reversed only partially the effect of kinetin while it completely reversed that of red light. P o w e l l and G r i f f i t h (1960) have reported a similarity in the action of red light and kinetin as both increased the Fig. 1. Effect of kinetin concentrations mediated with two different types of red light on the germination in the dark of the seeds of Plantago major. 42 expansion of discs from bean leaves and both caused greater elongation in stems and petioles of bean seedlings. They added that the action of red light and kinetin together caused a greater increase in size of discs, but kinetin has never physiologically replaced red light. In our results here there is a parallel similarity in action between red light and kinetin. Both of these two factors failed to promote the dark germination of the seeds of Plantago major. The combination of red light and kinetin gave results that are gra-phically represented in Fig. 1. It is clear from that figure that kinetin solutions mediated with red light from either sources could promote the germination of P. major seeds, but the promotions were higher on using red light from the fluorescent lamps. This difference in response to the different qualities of red light may be attibutable to the higher intensity of red light received from fluorescent lamps. Similar germination promotions by the use of the combination of red light and kinetin have been arrived at by different authors. An example of the synergistic effect of the red light and kinetin was given by K h a n and T o 1 b e r t (1965) who stated that the inhibitory effect of some naturally-occurr-ing seed germination inhibitors (coumarin and xanthatin) could be reversed only by a combination of red light and kinetin but not by either of them alone. With potassium nitrate the position was nearly the same as was with kinetin, a germination promotion was obtained when this salt at a concentration of 0.2 % was applied to the seeds in combination with red light from either sources. Table II shows the results of this experi-ment. It is again shown that the promotion was higher when red light was supplied from fluorescent lamps that it was when the source of red light was the iodine lamp with its interference filter. Table II. The effect of KNOa solution alone and mediated with red light from two different sources on the germination of Plantago major seeds in the dark. Seeds imbibed in 0.2% KN0 3 Germination for 24 hours, and then . . . Percentage Ked light from interference filter for one hour 29.30 Red light from fluorescent lamps for one hour 40.75 Dark Control 3.00 The results obtained with the germination of Carnegica gigantea seeds by A l c o r n et al. (1956) coincide greatly with our findings with Plantago major seeds here since those light-sensitive seeds were greatly promoted in germination only when subjected to a combined treatment with potassium nitrate solution and red light. T o o l e et al. (1955) also mentioned that Lepidium densiflorum and other light-sensitive seeds could only be promoted to germinate in the dark if they were supplied with potassium nitrate solution and irradiated with red light and they mentioned that germination was never initiated if the seeds were imbibed in potassium nitrate solution alone. 43 Summary Red light from interference filter or from fluorescent lamps could not promote the germination of the light-sensitive seeds of Plantago major. A combination of red light with either kinetin or potassium nitrate solutions could promote the germination of those seeds in the dark. Irradiation with red light from fluorescent lamps in combination with either of these two chemical substances gave higher germination percentages than when red light from the interference filter was used. Acknowledgment This research was carried out during a fellowship from the Hungarian government for which the author is very grateful. The author is also greatly indebted to Prof. Dr. I. H o r v á t h, head of the Botanical Institute of the József Attila University, Szeged for his interest in this work and his continual cristicism and valuable help. Thanks are also extended to Dr. K. S z á s z for measuring and ajusting the different light intensities. References A l c o r n , S. M. — E . B. K u r t z Jr. (1959): S o m e factors affecting the germination of seeds of the Saguaro Cactus (Carnegiea gigantea). — Amer. Jour. Bot. 46, 525—529. B o r t h w i c k , H. A. — S. B H e n d r i c k s — E. H. T o o l e — V. K. T o o l e (1954): Action of light on lettuce seed germination. — Bot. Gaz. 115, 205—225. D o w n s , R. J. (1955): Photoreversibility of leaf and hypocotyl elongation of dark grown red kidney bean seedlings. — Plant Phsiol. 30, 468—473. H o r v á t h , I. — K . S z á s z (1965): The quantitative measurement of the light in field and laboratory conditions. — Bot. Közlem. 52, 221—224. I k u m a , H. — K. V. T h i m a n n (1960): Action of gibberellic acid on lettuce seed germination. — Plant Physiol. 35, 557—566. K a h n , A. A. (1960): Promotions of lettuce seed germination by gibberellin. — Plant Physiol. 35, 333—339. K h a n , A. A. — N. E. T o l b e r t (1965): Reversal of seed germination inhibitors by red light and kinetin. — Physiol. Plant. 18, 41—43. M c D o n o u g h , W. T. (1965) Some effects of phosphon on germination induced by red radiation and gibberellic acid in seeds of Verbascum thapsus. — Plant Physiol. 40, 575—577. M i l l e r , C. O. (1956): Similarity of some kinetin and red light effects. — Plant Physiol. 31, 318—319. M i l l e r , C. O. (1958): The relationship of kinetin and red light promotions of lettuce seed germination. — Plant Physiol. 33, 115—117. M o h r , H. — U. A p p u h n (1963): Die Keimung von Lactuca Achanen unter dem Einfluss des Phytochromesystems und der hochengieraktion der Photomorpho-gesis. — Planta 60, 274—288. P o w e l l , R. D. — M . M. G r i f f i t h (1960): Some anatomical effects of kinetin and red light on discs of bean leaves. — Plant Physiol. 35, 237—275. R e z k , M. R. (1967): Studies on the light sensitivity of Plantago major seeds: I. The effect of gibberellin, kinetin, and potassium nitrate. — Acta Biol. Szeged. 44 T o o l e , E. H. — V. K. T o o l e — H . A. B o r t h w i c k (1955): Photocontrol o f Lepidium seed germination. — Plant Physiol. 30, 15—21. T o o l e , E. H. — V. K. T o o l e — H. A. B o r t h w i c k — S. B. H e n d r i c k s (1955): Interaction of temperature and light in germination of seeds. — Plant Physiol. 30, 473—478. Present Address D r . M a 1 a k R. R e z k Botany Department, Faculty of Science, University of Alexandria, Moharram Bey , Alexandria, U. A. R. 

Studies on the Light Sensitivity of Plantago major L. Seeds. II. The Effect of Red Light Alone and Mediated by Chemicals

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Studies on the Light Sensitivity of Plantago major L. Seeds. II. The Effect of Red Light Alone and Mediated by Chemicals

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