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Indian J. Plant PhysiQ/., Vol. XXVII, No.1 pp. 74-80 (January 1984)
EFFECT OF COMBINATIONS OF GROWTH SUBSTANCES ON LEAF ABSCISSION IN CHILLI AND THEIR 'INTERACTIONS' IN
THE PROCESS
KARAN SINGH· AND Y. S. MURTY
Department of Botany, Meerut University, Meerut (U.P), INDIA.
(Remed : JUDe 16. 1984)
SUMMARY
Experiments on NP 46·A and Pusa jwala varieties of Chilli (Capsicum annum L.) were conducted to study the action and <interactions' of certain growth substances in leaf abscission. Auxin, cytokinin and morphactin have shown additive <interactions' in retarding abscission when tested in combinations of two. Combinations where auxin was tested with abscis sion accelerants like gibberellin, ethylene and ~bscisic acid, later growth aubstances dominated in action resulting in abscission acceleration. The abscission accelerating action of ethylene and abscisic acid could only be partially counteracted by auxin and cytokinin. However, ascorbic acid failed to modify or reduce the action of auxin and benzyl adenine. Gibbe rellin has shown variety dependent variation in its effect when used in combination with cytokinin. Morphactin dominated in action in combin ations with abscission accelerants. Mutual <interactions' of any two abscission accelerants seemed to be non-additive in leaf abscission in general.
INTRODUCTION
Limitations of experiments using 'explant system' and 'debladed petiOle system' in studying the effects and 'interactions' of growth substances in leaf abscission process have been repeatedly pointed out (Addicott, 1981; Abeles,
1973)~ . Information obtained from such systems may not be useful to control abscission of leaves and other plant parts in agricultrual and horticultural crops (Cooper et; 01., 1968; Jacobs, 1979). Osborne (1974) has therefore, recommen ded to use 'whole plant system' for obtaining horticulturally important results with the application of growth substances. More recently, Sacher (1982) advoca ted to undertake comprehensive screening experiments using growth substances
in various combinations to get agriculturally important informations. Present investig~tions were, therefore, conducted on intact plant system to study the
ab :
Ar
'LEAF ABSCISSION IN CHILli 7S
effect of some growth substances on intact leaf abscission and also to study their 'interactions' in the process.
MATERIALS AND METHODS
Experiments were conducted on plants of NP 46-A and Pusa jwala varie ties of Chilli (Capsicum annum L.) during Feb.-Aug .• 1977 and repeated in same months during 1978 under ordinary field conditions. Plants of experimental varieties were raised in earthen pots and maintained in one stemmed and vigourous growth conditions following the recommended horticultural practices (Thompson and Kelly, 1957). Just one day before the start of treatments, pots with plants were arranged in RBD pattern. Plants were numbered 1-10. Each plant was tagged for leaf numbers 2·10 following the method of
Morgan and Durham (1973). At the time of treatments, plants were 4S days old and in 12th leaf fully unfolded stage. Freshly prepared test solutions of individual growth substance in single most effective concentration as determined by earlier experiments (Singh and Murty. 1983) and combinations of growth substances were sprayed on plants to wet them upto dripping off stage by hand sprayer four times on two consecutive days. Tween-20 (0.002% V/V) was used as surfactant. Plants treated with water
+
Tween-20 served as contro1The pre-abscission periods of leaf 2.6 and 10 were recorded following the method of Singh and Murty (1983). Growth substances and their respective concentrations and combinations are given in tables 1. and figure 1. Some
Table I : Pre-abscission periods (day) of leaves of chilli varieties spray treated with solutions of individual growth substances
Control Pre-abscission periods (days) in response to treatments
Variety Leaf PP NAA BA CME GA ETH ABA AA
No (days) 100 ppm 20 ppm 20 ppm 100 ppm 200 ppm 10 ppm 200 ppm
2 10.20 16.30 19.40 22.00 03.30 04.30 05.10 02.80
NP46-A 6 21.30 2910 31.50 41.00 13.10 13.60 13.10 09.30
10 37.30 51.40 49.20 57.44··· 2S~60 21.60 27.30 22.00 LSD-2.65
2 12.30 20.80 19.40 23.00 07.00 05.30 07.20 02.30
Pas jwala 6 3020 39,80 33.00 41.70 15.10 13.10 13.50 13;00 10 46.20 57.60 53.44·· 59.66·· 34.20 26.20 34.50 25,50
LSD-3.50
All figures (except those marked by·· and .U) are averages of 10 •
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76 KARAN SINGH AND Y.S. MURTY
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VARIETY-NP- 46-4 ~ NO· OF L£AF7 2
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SO
6
CJ
10GIl
~
VARIETY. PUS4 JWAlA
NO· OF L£Af
o 10 • 46
a 2
•
iGROWTH SUBSTANCES ( COMBINATIONS r
Fig. I. Pre-abscission preriods (days) of leaves of varieties of Copsicum annuum L. in response to treatments with combinations of seven growth substances. (Stan dard abbreviations-Addicott 1981-used).
leaves on few plants did not abscise till the termination of experiments. Such abnormal figures were excluded from averaging so that means in such cases were ofoine (marked by **) or eight (marked by·**) figures only. Standard abbreviations (Addicott, 1980 were used.
RESULTS AND DISCUSSiON
Inferences concerning the possible and apparent 'interactions' of growth substances in affecting foliar abscission were drawn from the comparative analy sis of data obtained in response to spray treatments with individual growth : substances (Table-I) and combinations of eaeh two of them (Figure 1).
(A) Effect and 'interactions' of abscission .retardants :
LEAF ABSCISSION IN CHILLI 77
i1!
23.
2u; .ment of pre-abscission periods of leaves by the combinations like NAA + BA and NAA+CME. The later combination proved to be slightly more effective than former in both varieties. 'Interaction' of BA with CME also proved to be additive but to a lesser extent than that of NAA+CME (Figure I) .. However, the growth abnormalities stimulated by individually applied morpbactin were not observed in plants treated with BA+CME. This combination may be horti. culturally valuable in retaining leaves for relatively longer period on plants. The additive 'interaction' of auxin with cytokinin may be attributed to the main tanancl!: of high levels of endogenous auxins and cytokinins which are considered as the natural retardants of abscission via senescence in whole plant system (Wareing and Seth, 1967). Cooper et al. (1968) and Addicott (198 I) have
shown that the leaf abscission retarding action of auxin and cytokinin in combi nations was primarily due to their capacity to maintain the abscission zone in a state of juvenility, reduced IAA oxidase activity and ETH biosynthesis. Dybing (1977) with peas and SalmInen and Gagianas (1972) with bean reported a synergistic and additive interaction of morphactin with auxin and cytokinin in seecence which may be accounted for an additive abscission retardation by their combinations in present investigations.
(B) Effect and 'interactions' of abscission retardants witb accelerants :
Auxin and gibberellin combination significantly accelerated leaf abscission . in both the varieties but auxin appeared to reduce abscission accelerating effect of gibberellin. The potent action of ethephon in abscission acceleration was considerably lowered by NAA. Abscission of all the three tested leaves was accelerated by auxin and abscisic acid combination. In combination with auxin, ascorbic acid could not mask the strong abscission retarding effect of auxin. Retardation stimulated by NAA and AA combination was even more than that stimulated by individually tested NAA in NP 46-A. But in Pusa jwala, AA seemed to reduce marginalJy the effect of NAA (Figure
O.
Production of ·ethylene by GA as reported by Biggs and Leopold (1957) may be regarded responsible for acceleration of leaf abscission by NAA and GA combination. Jacobs and Kirk (1966) have also reported tha~ GAwas able to counteract the abscission retarding action of auxins. Morgan and Durham (1973) reported that exogenously applied ETH drastically reduced endogenous auxin level leading to abscission acceleration. Milborrow (1974) concluded that abscission stimulatory action of ABA may be atributed to its capacity for enhancing an excessive endogenous ethylene production. Hartmann et. al.
78
~
JA
4.)
t
KARAN SINGH AND Y.S. MURTY
Abscission of all the tested leaves was significantly retarded by cytokinin and gibberellin combination and GA could not rem~rkably reduce the action of BA in NP 46-A. However, GA could successfully antagonise the effect of BA in Pusajwala where pre-abscission periods of leaves were almost similar to the comparable leaves of 'control' (Figure
O.
Cytokinin and ethylene as well as cytokinin and abscisic acid combinations have shown significant shortening of preabscission periods of leaves in both varieties. Ascorbic acid could not alter the strong abscission retarding effect of cytokinin. Results of BA +GA combina tion are in agreement to those reported by Halevy and Wittwer (1966) in some vegetables and ornamental plants. The action of ethylene released from exo genously applied ethephon and synthetic abscisic acid i!l strong enough to modify the effect of cytokinin (Leopold, 1971). Results of BA+ETH and BA+ABA combination in present studies also support the above mentioned view.Thougb, tbe abscission retarding effect of morphactin could not be counteracted by the addition of gibberellin to the solution, it was observed that growth abnormalities stimulated by individually tested CME, were deferred by the presence of gibberellin in the solution. Morphactin proved to be such a strong abscission retardant tbat ethylene, abscisic acid and ascorbic acid almost failed to counteract its effect. Present observations on the 'interactions' of morphactin with abscission accelerants are in accordance to the findings of Schneider (1970) who has reported that the addition of gibberellin or ethylene or abscisic acid did not alter or modify the action of morphactin in most of the pbysiological phenomena of plant growth. However, no satisifactory explana tion can be offered at present for the dominance of CME, even over the strong absicission accelerants like ETH and ABA. Parups (1983) has emphasiZed on more experimentations to know the mode of morpbactins in abscission and senescence.
(C) Effect and 'interactions' of abscission accelerants:
Combinations like GA+AA have significantly accelerated leaf abscission but the 'interaction' of the accelerants did not appear to be additive in general. The 'interactions' of ethylene with abscisic acid proved to be additive in majority of leaves under study. Though, abscission of leaves was significantly and sequen tially accelerateo by ethylene and ascorbic acid combination as well as by abscisic acid and ascorbic acid combination, none of these combinations caused an additive effcct on leaf abscission in chilli varieties (Figure
O.
rsU)W'
LEAF ABSCISSION IN CHILLI 79
using Coleus has confirmed that the stimulation of endogenous ETH biosynthesis under ethrel, abscisic acid and gibberellin (higher doses) treatments increased tremendously the activity of 'cellulases' which are positively involved in leaf abscission. It may be concluded from these investigations that combinations like NAA+BA, NAA+CME or BA+CME may be applied horticultura11y to retain leaves for longer periods on plants while combi'nations like ETH+ABA, ETH+AA, ETH+GA or GA+AA may be used to facilitate harvest practices.
REFERENCES
Abeles, F.B. (1973). Ethylene in Plant Biology, Academic Press, New York.
Addicott, F.T. (1981). Abscission. ppl-12. University or California Press, Berkely California.
Biggs, R.H. and Leopld, A.C. (1957). Factors influencing, abscission. Am. J. Bot., 32: 626· 632.
Cooper, W.C., Rasmussen, G.K., Rogers, B.J. Reece, P.C., Henrry, W.A. (1968). Control of abscission in agricultural crops and its phYsiological basis. Pla1lt Physiol., 43: 1560-1576.
Dybing, C.D. (1977). Delayed senerscene offlax treated with morphactins and anti-auxins. Proc. plant Growth Re,. Group, 4 : 207-210,
Halevey, A.H. and Wittwar. S.H. (1966). Effect of growth relardants on longevity of vegata bles and cut flowers Proc. Amer. Soc. Hart. Sci., 88 : 582·590.
Hartmann, H.T. Fad!., M and Whisler, J. (1967). Inducing abscission of olive fruits by AA and IAA. Calif. Agrie., 21 : 5-7.
Jacobs, W.P. (1979). Plant hormones and Plant development. Cambridge University Press. pp 209-221. London.
Jacobs, W.P. and Kirk. S.C. (1966). Effect of gibberellic acid on elongation and longevity of Coleus petioles, Plant Physiol., 41 : 487-490
Leopold. A.C. (1971). Physiological processes involved in abscission. Hart. Sci., 6(4): 376-378.
Milborrow, B.Y. (1974), The chemistry and Physiology of abscisic acid. Ann. Rev. Plant Physio/., IS : 259:307.
Morgen, P.W. and Durham, J.I. (1973). Leaf age and ETH induced leaf abscission, Planta, UO: 91.96.
Osborne, D.J. (1974). Hormones and the shedding ofleaves and bolls, Cotto Grow Rew., 51 : 256-265.
Parups, E.Y. (I983). Physiology and biochemistry of morphactins. In Aspects of Physioio,y and Biochemistry ofPlant Hormones. pp 255-290 (Ed.) S.S. Purohit, Kalyani Publi sbers, Ludbiana and New Delbi.
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80 KARAN SJNGH AND Y.S. MURTY
Sacher, R.M_ (1982). Strategies to disscover plant growth regulators for agronomic crops. In Chemical Manipulation 0/ Crop Growth and Development pp. 13-18. Butterworlbs. London.
Schneider, G. (1970). Morphaetins: Physiology and Performance Ann. Rev. Plant Physiol., 21 : 499-537.
Singh, K. and Murty, Y.S. (1983). Intact leaf abscission responses of Chilli to aqueous spray treatments with growth substances. Adv. Bioi. Res., 1fl) : 13-21.
Thomposon, H.C. and Kelly, W.C. (1957). Vegetable crops. Me Graw Hill Book Co. New York.
Wareing, P.E. and Setb, A.K. (1967). Ageing and senecence in the whole plant, In Aspects 0/Biology 0/Ageing (Ed.) H. W, Woolhouse. pp 543-558. Cambridge University Preis.
