Kobe University Repository : Kernel

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1 Kobe University Repository : Kernel タイトル Title 著者 Author(s) 掲載誌 巻号 ページ Citation 刊行日 Issue date 資源タイプ Resource Type 版区分 Resource Version 権利 Rights DOI STUDIES ON THE PERMEATION OF UREA INTO LEAF CELLS : Contribution to the Foliar of Urea I.( 尿素の葉面細胞透過に関する研究 ) Horie, Kakuro 兵庫農科大学研究報告. 自然科学編,1(2): Departmental Bulletin Paper / 紀要論文 publisher JaLCDOI / URL Create Date:

2 STUDIES ON THE PERMEATION OF UREA INTO LEAF CELLS* Contribution to the Foliar of Urea J.-- By Kakura HORIE (Botanical Laboratory) In recent years it has been reported by some authors that \'arious kinds of horticultural crops respond fayorably to the foliar application of urea. There has, however, been very little attention paid yet to the physiological behavior of cells to which urea was applied for this practical purpose. The present paper is a preliminary report on stl1dies which were undertaken to find any changes of the osmotic concentration and of the urea-permeability of the cells of leaves treated with urea. Several investigators',") have reported that leaf injury was sometimes causer! by the urea sprays, while others",1.1;) have noted that it was markedly reduced when sucrose was added to the spray soll1tion. This action of Sl1erose was, therefore, taken into consideration in the present case, in the theoretical meaning as well as for the practical pnrpose. The author wishes to express his cordial thanks to Professor Hideo Hamada for his interest and criticism. Thanks are also due to Mr. Minoru Matano and 1\11'. IIfasahito "'1iki for their assistance in carrying out the experiment. Material and Methods The Akamaru variety of radishes (Raphanus sativ!(s) was used as the experimental material. It was suitable for use in the present studies because of the rapid growth of the leaves, The seeds were sown in ll-inch earthen pots on March 25, Four plants in each pot were grown and kept in the glass-house. Soil from the grounds out of the bloratory was used withont any addition of fertilizer. The plants were divided into three plots, each containing ]2 plants in total. The daily foliage spray began from April ]0, when the plants had developed four or five leaves. The first plot was sprayed with a 0.5 per cent nrea solution and the same solution added with 0.1 M sucrose was applied to the second plot. The r('main' ing plot was not sprayed and used as the control. The spray IVas applied on both surfaces of the lca\'cs with a small hand sprayer at four o'clock each afternoon. About 2 cc of the solution was sprayed on each plant at the start of the experiment. \,yhen the plants grew up the amount was increased up to about ]0 cc per plant. No wetting agent was used. During the spray the surface of the soil was entirely covered with sheets of pasteboard, so that no drop of spray solution could reach the soil. The microscopical obscfyation was made between one and four o'clock 111 the afternoon, before the plants had been sprayed. The epidermal cells, especially the hairs protruding from the lower surface of veins of mature leaf were used for the present experiment as they first came into contact with the spray solution. The hair cell s of larger size than the other epidermal cells, were ascertained to act osmotically in a similar manner to the other ones. The osmotic concentration of the cells was determined by the plasmolytic method, placing them in sucrose solutions of a series of graded concentrations. The cells were immersed in the solutions C or half an hour before the microscopical observation was made. \,yhen the plasmolytic experiments had been finished, the plants were harvested on May 5. They were washed separately with distilled water, dried to constant weig-ht ami total nitrog-en was determined by the Kjeldahl method. * The present study has been supported in part by a grant 111 aid for Development of Scientific Research from the Ministry of Education. 35

3 Sc. Rep. of Hyogo Un!Y. of Agric. Vol. 1, No.2 Results and Discussion a) Osmotic concentration of hair cells. Ten obseryations were made in the same manner from April 21 to May 5. The osmotic concentration at the.incipient plasmolysis was determined. The average values are presented in Table 1. Table J. Osmotic concentration (mol) at incipient plasmolysis of hair cells of radish leaves Urea I Urea + Sucrose I Control Concentration D3~J ~ ~(~ I~;~~_ The daily application of urea spray did not cause any increase of the critical concentration, either in the urea-sprayed or the urea-plus-sucrose-sprayed material. According to Cook and Boynton"', 34 per cent of urea, absorbed from leaf surface of apple tree, still remained in the leaves after 3 hours, and it gradually decreased to 65 per cent after 24 hours, and to 43 per cent after 43 hours. They also noted that non-soluble nitrogen fraction in the sprayed apple leaf did not increase enough to account for the disappearance of urea. As the easy permeati()!1 of urea into the cell is concei,- able in the present experiment, it may be assumed that the most part of the absorbed urea was probably translocated from hair cells to the neighboring tissues at the latest in 24 hours. But in view of the fact that the osmotic concentration of the urea-sprayed material was a little lower than that of the control cells, it may not be improbable that a part of the absorbed mea was united to sugar in the cells to form protein thereby decreasing the concentration of the cells. b) Permeability of hair cells to urea. The following experiment was made to learn whether the permeability of cells to urea was infiuenc~d or not by the daily urea spray. The osmotic concentration of cells at the incipient plasmplysis (C 1 ) was first determined with sucrose sol utions. The same materials were next immersed in the mea solution whose concentration was equivalent to the critical. After an hour they were taken out from the solution and determination was made of the second critical concentration (C 2 ), which was usually higher in some degree than that obtained initially. The relative perl11eabiliy of the cell to mea was expressed as follows: C 2 -C ---C- 1 - x JOD. The indiyidual cells. e\'en in one and 1 the same section of a tissue, sometimes showed different values of the critical osmotic concentration. In such cases the second determination of osmotic concentration had to be made with the individ ual cells. In this way ten determinations were carried out from April 21 to May 5. The average values are presented in Tabel 2. The relative urea-permeability of the cells of the urea-sprayed material was higher than that of the control cells. It seems that daily foliar spray with urea solution has a tendency to make the epidermal cells more permeable to urea. This increasing tendency of urea-permeability is more remarkable in the case of spraying with urea solution mixed with sucrose. This is of special interest in connecion with the fact that sucrose rather reduced the permeation of urea into the leaves. referred to I ater on. The fact last mentioned will be c) Growth and total nitrogen content of radish plant. In Fig. 1. are shown the sizes of radish plants grown in three separate plots (May 5). The plants in two plots, which were daily sprayed, grew equally in large size and vigorously, though a little better growth showed in the plants \\ ithollt addition of Table 2. Relative permeability of hair cells to urea Urea Urea + Sucrose 1- Control Initial osmotic concentration (mol) at incipient plasmolysis (C 1) Second osmotic concentration (111 01) at incipient " plasmolysis (C 2) Increase of osmotic concencentration (111 01) (CZ-C 1 ) Relative permeability to urea (C'CI C 1 x 100) ~~ D.CG ~---- I

4 XII, 1954 sucrose. T he!eaves were also equally dark green, but in the case of the latter treatment leaf omning was caused, though 1I0t remarkably. According to the writer"s previoll> eapcriment the radi3h plant was affected by a severe leaf burning by the spray \\ith 1 per cent urea solution. The control plant was small and dwarf, and the leaves were yellowish green. All the test plants were harvested on May s. The leafand rootparts were separated and the total nitrogen was determined in the same manner as mentioned Table 3. Series; Natural Science f: c Fig. J. 1. u u+s The growth of radish plants in three different plots on May 5 (41 days after the sowing ancl 25 days after the beginning of foliage spray). C; control, U: sprayed daily with a 0.5 per cent urea solution alone, U + S : sprayed daily with a 0.5 per cent UfCo'1 solution mixed with 0.1 M sucrose. Dry weight antl nitrogen content (mg) of radish plant Urea Urea + Su Crose Control leaf root leaf root leaf root Dry weight 1,131 2,47G 1,026 Total nitrogen Total nitrogen per cent dry weight _ ' ,1(;2 435 ],4] ].62 previously. The average values obtained from five materials of each plot are given in Table 3. sprayetl materials were much T wo larger both in dry weight and in total nitrogen than the contra). Espe Cially the leaf total nitrogen of the urea-sprayed material amounted to five times as much as that of the control or more and to 5.48 pcr cent dry weight. The influcnce upon the plant growth by sucrose added to urea is more clearly seen from Table 4. It showed t hat thc tl ecrcase of l(!af total nitrogen by the addition of sucrose amount-~d to 37 pcr cent, while the decrco'1se of leaf dry weight amounted only to 9 per cent. Similar results were also obtained in the case of the root. T herefore, it is probable that the use of StlCrose, mixed w;th urea for the purpose of spray, particularly limited the pcrt11<'ation of urea into the leaves. Hinsvark et at.") have noted that the addition of sucrose reduced the injury to tomato leaves caused by urea. Table 4. Decrcase of dry weight and nitrogen content of radish plant by addition of sucrose to urca* Dry weight (?O) Total nitrogen (%) _ Total~~gcn ~~ cent dry weight (9':;) L~ I 91 B7 I *In this table the val lies were calcl1 late<:l from Table :3, taking the respective val lies nhtained hom the mea-alone material as standartl. 37 According to their view sucrose exerts a pr:!venting influence on the foliar burn- ing of the tomato plant by an inhibiting power against the urease activity. This inhibition may be cl ue to the preventio n of rapid accumulation of toxic hydrolytic products of urea. Noguchi antl Sugawara 7 ) However, have reported that the urease activity was extremely weak in the urea-sprayed leaves of tomato and radish. From the results of the present experiment it may be rathej

5 Sc. Rep. of Hyogo. Univ. of Agric. Vol. 1, No.2 assumed that the reduced effect on the leaf injury which resulted from the addition of sucrose to urea, is primarily due to the decrease of permeation of urea into the leaves, as stated by Cook and Boynton") in the case of McIntosh apple leaves. In practice sucrose may be advantageously recommended as a supplementary agent, because it regulates moderately the permeation of urea into the leaves, without marked decrease of the characteristic value of spraying with urea. Summary Alwmaru variety radishes were grown in the glass-house. The first plot was daily sprayed with a 0.5 per cent urea solution, and the second plot was sprayed with the same solution but with addition of 0.1 M sucrose. The third plot was not sprayed an,l was used as the control. a) The osmotic concentration at the illci"i~nt plasmolysis of the hair cells of leaves was determined. There was found no significant difference in this connection among the three plots. The most part of urea absorbed by the epidermal cells probably translocated to the inner tissues at the latest in 24 hours. b) Permeability of hair cell to urea was measured by the plasm:jlytic method. The daily foliar spray of urea solution had a tendency to make the epidermal cells more permeable to urea, especially so when urea solution mixed with sucrose was used. c) The plants which were 'daily sprayed with mea solution, regardless of the addition of sucrose, grew to larger size and more vigorously than the control. Moreover, no remakable burning was seen in their leaves and they excelled the control both in dry weight and in nitrogen content. The addition of sucrose to urea in spray, decreases particularly the permeation of urea into the leaves and thereby reduces the leaf injmy caused by the application of mea alone. (Received August Ul, ]'>54) Literatur~ 1) Bonn'oN, D. and Fr.;cllIm, E.; N cw Jersey State Hart. Soc. News. 32: 2425, ]95]. 2) COOK, J. and BOYNTON, D.; Proc. Amer. Sue. Hart. Sci. 59: HZ, ]<)32. 3) EmlErn', E. M. alld KLINK:n, J. E. ; Kentucky Agr. Ex p. Bull. 550: ], 1<)50. 4) F[,~:\![N<l, H. K. and ALr<:XANI);':~, R B.; Proc. Amer. Soc. Hart. Sci. 5<1 : ]7], ]949. 5) HA,\!f[,TON, J. M. and PAL\![I'''~, D. II.; Proc. Amer. Soc. Hart. Sci. <12: ]23, ]943. 6) H[N~VAHK, u. N. et al.; Pilmt Physiology. 28: 70, ]953. 7) Pi Q lilh'i, 'i'\'jj;uc;((; ::ic,'oi; tif'i ";::)~f&.lijf'ji:: ')j~ ;ri', 16: ], B