,, 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.