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ANALYSIS OF PETIOLE-LONGEVITY AT DIFFERENT STAGES OF REPRODFCTIVE PHASE IN MANGO (AfANGIFERA INDICA L.) VARIETIES, LANGRA AND FAZLI

B. C. MAZUMDAR and S. K. CHATTERJEE

Department of Botany, Universi(Y of Burdwan, Burdwnn, H'est Bengal

Received on December 12, 196H

SuMMARY

This paper deals with the study of differences m the longevity of de-bladed petioles during pre-flowering, flowering and post­ flowering stages in two commercially popular varieties of mango, viz., Langra and Fazli. The retention period of the de-bladed petioles varied in nvo varieties and was shortened during the succeeding reproductive stages. A varietal difference was observed in the mechanism of control of petiole-longevity by exogenous application of abscission regulators, , viz., NAA, GA3 ascorbic acid and ethylene gas. The auxin-inhibitable stage I of abscission, as reported by Rubinstein and Leopold (1964) was found to occur in mango also.

INTRODUCTION

The phenomena of leaf-longevity and abscission have been studied in many plants. The biochemical mechanism control­ ling the longevity of a plant organ has been reviewed by Jacobs (1962). Acharyya Choudhuri and Chatterjee (1968) have shown that a distinct change in the longevity aspects of de-bladed petioles of Coleus occurs during the time of flowering. An identical behaviour in cotton has been shown by Roy and Chatterjee (1967). In mango different stages of flowering, namely pre­ flowering, flowering and post-flowering succeccl one after another , within a short duration of time. It was considered interesting to follow how the phenomenon of longevity of de-bladed petioles varies during these developmental stages. Two varieties of PETIOLE ABSCiSSION AND REPRODUCTIVE PHASE IN MANGO 189

mango, viz., Langra (mid-season) and Fazli (late), which are commercially popular and are grown in the plains of West Bengal, were used for this investigation.

MATERIALS AND METHODS

Healthy shoots (4-7 month old) with about ten fully grown dark-green 1ea,·es on each, were collected from Langra and Fazli mango trees of 15-20 years of age, discarding the shoots bearing panicles. The apical leaves, arranged in whorls on these shoots were de-bladed leaving behind 2-cm length of petioles from their axils. Naphthalene acetic acid (NAA), ascorbic acid (AA) and

gibberellic acid ( GA3 ) in lanolin bases were applied to the cut ends of the petioles. For application of ethylene gas, the de­ bladed shoots were kept in gas-chambers, that were previously evacuated partly and were injected with the requisite concen­ tration of ethylene gas, for 24 hours. The experiments were conducted in a growth room under a photoperiod consisting of 12 hours of light and 12 hours of dark at a temperature varying from 20 to 35oC and R.H. from 70-80 per cent. The chemical treatments were given during (i) the pre­ flowering stage-just prior to visual emergence of panicles­ lasting from November to end of January; (ii) the flowering stage -from visual emergence of panicles to· their full elongation when majority of the flowers had opened-lasting from early February to March; and (iii) the post-flowering stage-from pea-stage of the fruits set to attainment of 1-cm diameter-lasting from the end of March to the first week of May in variety Langra and a fortnight later in variety Fazli. The abscission process was considered to have completed when the petioles detached easily by slight mechanical pressure. The experiments were replicated 4 times with comparable results. The L.S.D. (at 5 per cent kvel) in the abscission response varied from 6 to 8 hours.

RESULTS

Control time of abscission.-The pre-abscission time of the de-bladed petioles of two varieties at different developmental stages is shown in Table 1. 190 B. C. MAZUMDAR AND S. K. CHATTERJEE

Table I. Control time for 50 per cent abscission of two varieties at different developmental stages

Hours required for 50 per cent abscission in Stages var. Langra var. Fazli

Vegetative (July-August) 80-92 99-105

Pre-flowering 70-75 84-87

Flowering 54-62 68-72

Po~t-flowering 30-40 36-47

The times for 50 per cent abscission decreased with an advancement in the developmental stages so that the time taken for abscission was the least during the post-flowering stage, being on an average 35 and 42 hours in varieties Langra and Fazli, respectively. Fig. 1 shows the 50 per cent abscission time of the de-bladed petioles of two varieties at fortnightly intervals.

....00 !00~------~ §l ..c 90 .s ·~ 80 .§ 70 ·u~ 60 $ ~ 50 "u b 40 0.. ~ 30L--r--~-r--~~--T-~--~~--~~--.-~--~ Nov Dec Jan Feb Mar Apr May .Jun Months of the year

Fw. I. 50% abscission of the de-bladed petioles of the two varieties at fortnightly intt>rvals (November-middle of J uncI. Continuous lint' ( --)= var. Langra Broken line ( ...... ) = var. Fazli

The pre-abscission time in var. Fazli remained higher than that in var. Langra during all the developmental stages. It may be noted that at the completion of the post-flowering stage, the abscission time tended to increase slightly in both varieties, PETIOLE ABSCISSION AND REPRODUCTIVE PHASE IN MANGO 191

Longevity behaviour in relation to NAA, GA , AA and Ethylene 3 gas.-The changes of pre-abscission time due to application of

0 · 25 per cent NAA, AA, GA3, and 3 · 30 per cent ethylene gas are shown in Tables II-V, respectively. It is observed that NAA completely inhibited abscission at pre-flowering, flowering and post-flowering stages and this inhibition was erased vvhen NAA was applied 12 hours after de-blading at all stages in both varieties except in var. Fazli, where promotion was obtained 24 hours after de-blading. The extent of inhibition was higher in var. Langra, when applied immediately after de-blading during all the three stages.

Table II. Effect of NAA (0· 25 per cent) applied at different times after de-blading during different developmental stages in the two varieties

--~---- -~------··------·------Hours of inhibition ( +) or promotion H for 50% abscission applied at (hours) Stage Varieties ------0 th 12 th 24th Langra (+) 88 (-) 12 Pre-ffowering (-) 23 Fazli ( +) 17 (-) 10 (-) 4 Langra (+) 148 (-) 15 Flowering (-) 18 Fazli (+) 98 (+)59 (-) 25 Langra (+)51 (-) I Post-flowering (-) 8 Fazli (+) 2 (-) 10 (-) 15

Table III. Effect of AA (0·25 per cent) applied at different times after de-blading during different developmental stages in the two varieties

------·-----·· ----·------··------·------" Hours of ir1hibition ( -1-) or promotion (-) for 50% abscission applied at (hours) Stages Varieties ---- 0 th 12th 24th Langra (-) II (-) 16 Pre-flowering ( -) 23 Fazli ( --) Hi ( i-) 2 (-) 9 Langra (-) 17 (-) 19 Flowering H 18 Fazli (-)23 (-) 16 (-) 10 Post-flowering Langra (+) 3 (+) 7 (+) 5

Fazli (±) 0 (+)I (+) 5 192 B. C. MAZUMDAR AND S. K. CHATTERJEE

AA shortened the pre-abscission time in all the treatments (i.e., at 0, 12th and 24th hours of deblading) during flowering stages in both varieties. The abscission time did not differ much from the controls during the post-flowering stage. In the pre-flowering stage AA caused promotion in var. Langra (Table III).

( Table IV. Effect of GA 3 0 · 2 5 per cent) applied at different times after de-blading during different developmental stages in the two varieties

Hours of inhibition ( +) or promotion (-) Jar 50~~ abscission applied at (hours) Stages Varieties 0 th 12th 24th

Langra (-)31 (-)41 Pre-flowering H 33 Fazli H l ( -: ) :z H 18 Langra (-) 19 (-):!! (-) 26 Flowering Fazli (-) 2H H 35 H 3.i Langra ( -:-) 13 ( ) 3 ( _L) 0 Post-flowering Fazli (-) 4 (-)4 (-) J

GA3 caused promotion of abscission during pre-flowering and flowering stages and the extent of promotion was higher in var. Langra during pre-flowering and in Fazli during flowering stage. In general, the post-flowering treatments showed

weaker response towards GA3 treatments in both varieties (Table IV).

Table V. Effect of exposure to 3 · 30 j;er cent ethylene gas for 24-hours at dijferent times after de-blading at different developmental stages in the two varieties

Hours of inhibition ( +) or promotion (-) fur 50% abscission applied at (hours) Varielics 0 th 12th 24th

Pre-flowering Langra (-) 33 (-)31 H 33 Fazli H 17 (-)27 H20 Flowering Langra H 14 H 14 (-i 23 Fazli (-)31 H 36 H 27 Post-flowering Langra (-)2 (-) 6 H 10 Fazli (-)3 H 12 H 13 PETIOLE ABSCISSION AND REPRODUCTIVE PHASE IN MANGO 193

Promotion due to application of ethylene gas was obtained in both varieties during all stages. Promotion was maximum during flowering stage in var. Fazli and during pre-flowering stage in var. Langra. Post-flowering stages showed lesser promotion in both varieties (Table V).

DISCUSSION

The role of leaves on the control of flowering in mango has been demonstrated by Singh ( 1961) and Singh et at. ( 1962). In the present paper, an attempt has been made to investigate the effect of developmental stages of mango plant on the pheno­ menon of petiole-longevity. Petiole-longevity, as determined by its pre-abscission time has been studied in a variety of plant materials, viz., Phaseolus (Biggs et al., 1958; Chatterjee and Leopold, 1963; Gaur and Leopold, 1955), Coleus (Jacobs, 1962; Acharyya Choudhuri and Chatterji, 1968), Gossypium (Hall et al., 1961; Addicott et al., 1951, 1954, 1955; Carns et al., 1961). These studies have esta­ blished the physiological and biochemical control of the pheno­ menon. Acharyya Choudhuri and Chatte1jec (1968) showed the seasonal implication in the control of longevity of the petioles of Coleus. The sharp decline in pre-abscission time of the de-bladed petioles of two varieties of mango during flowering and post­ flowering stages suggests that the reproductive phenomenon may be involved in the control of longevity of plant organs. The mobilization phenomenon in the reproductive organs increases at flowering and post-flowering stages (Williams, 1955; Shiroya et al., 1961), which might cause a shift in the endogenous abscission regulators at the abscising zone, thus shortening the pre-abscission time of the de-bladed, non-productin~ shoots. A varietal difference in the mechanism of control of petiole­ longevity by abscission regulators is observed. Thus, the inhibi­ tion response in var. Langra towards NAA was more as compared to var. Fazli. The two varieties, however, did not ditlcr in their sensitiveness towards ascorbic acid. Sensitiveness towards gibberellic acid in these two varieties was difrercnt during different stages of flowering and promotion of abscission was higher during pre-flowering stage in the var. Langra and during flower­ ing stage in the var. Fazli. Such a tendency was also observed in the varietal response towards ethylene. All these observations 194 B. C. MAZUMDAR AND S. K. CHATTERJEE suggest that in an attempt to elucidate the abscission control in a plant, the response of its varieties might provide some important clues. More recently some interesting variations in the occur­ rence of abscission-regulators have been reported by Bhardwaj and Abrol ( 1968) in Gossypium. The auxin-inhibitable stage I of abscission, as reported by Rubinstein and Leopold (1964), occurs in mango as well. In general, this auxin-inhibitable stage is completed withinl2 hours of de-blading in both the varieties at different reproductive stages. The duration of auxin-inhibitable stage was shown to be greater (up to 24 hours) in var. Fazli. It could thus be pointed out that the participation of distinct stages of abscission was of general occurrence but the nature of participation might change during different developmental phases and also in varieties. The chemicals differ in their effect during different stages of reproduction. Thus, NAA-sensitiveness was higher during flowering stage in both varieties, whereas sensitiveness towards

GA3 and ethylene gas varied in the two varieties at pre-flowering and flowering stages. During post-flowering stage the respon­ siveness towards N AA, AA, GA3 and ethylene gas was weak in both the varieties. It could be concluded that the mechanism of abscission control is associated with the developmental physio­ logy of a plant and in mango the different reproductive growth may direct this mechanism of control in a distinct way.

AcKNOWLEDGEMENTS

The authors wish to express their deep sense of gratitude to Professor P. N. Bhaduri, Head of the Department of Botany, Burdwan University of Burdwan, for providing laboratory and other facilities and to the Indian Council of Agricultural Research, for offering the Senior Research Fellowship in Horticulture to the principal author of the present investigation, which enabled him to carry on the researches.

REFERENCES

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