P.O. Box 5083, Sunshine Coast Mail Centre, Nambour, Queensland, ... growth and flowering of two litchi cultivars in subtropical Queensland was investigated.
Journal of Horticultural Science (1986) 61 (1)
135-13~
The effect of cincturing at different stages of vegetative flush maturity on the flowering of litchi (Litchi chinensi Sonn.)* By C. M. MENZEL and B. F. PAXTON Maroochy Horticultural Research Station, Queensland Department of Primary Industries, P.O. Box 5083, Sunshine Coast Mail Centre, Nambour, Queensland, Australia, 4560 SUMMARY
The effect of branch cincturing at different stages of vegetative flush maturity on the growth and flowering of two litchi cultivars in subtropical Queensland was investigated. In cv Bengal there was a strong increase in flowering when a branch with dormant vegetative growth was cinctured and a smaller increase with a branch in early or late flush. Flowering was not improved with a branch in mid-flush. In cv Tai So there was a reduction in flowering when a branch in early flush was cinctured. Cincturing at any other stage had no significant effect on flowering. The proportion of young to mature leaves on the branches (as indicated by average leaf weight) decreased as the flushes matured. The responses at different stages of flush development is considered to be a reflection of this ratio at the time of cincturing and its influence on the relative accumulation of flower inhibiting and promoting substances above the cincture. IT is generally believed that litchi trees (Litchi chinensis Sann.) need a period of vegetative dormancy in winter to flower successfully in spring (Menzel, 1983). This dormancy is normally induced by moisture stress or cold, although it can be artificially induced by manipulative techniques such as withholding irrigation and fertilizers, the application of growth regulators, root pruning and cincturing (or girdling). Nakata (1953, 1956) was the first to demonstrate the response of litchi trees to cincturing. He promoted flowering and yield by up to 15 times with cv Brewster in Hawaii. The control plants tended to remain vegetative and flowered poorly. The highest yields were obtained after cincturing in September, three months prior to the normal period of floral initiation. The response to cincturing, however, has not always been consistent, as reviewed by Menzel (1983), and cannot always be explained by differences in climate, cultivar, tree nutrition or tree vigour. An alternative explanation lies in the possibility that the trees or branches were cinctured at different stages *Also known as 'lychee'.
of vegetative flush maturity. Preliminary observations by Nakata (1953) suggested that cincturing did not promote flowering after a new flush had been initiated. This paper reports the results of further investigations on the response of litchi to branch cincturing at different stages of vegetative flush maturity. MATERIALS AND METHODS
Experiments were conducted on six-year-old cv Bengal and cv Tai So litchi trees at Nambour, Queensland, Australia (lat. 27°S) in 1983. The trees were fertilized four weeks before and two weeks after harvest of the previous crop with 138 g N, 38 g P and 115 g K per tree. Irrigation was withheld from April to September. The phenology of each cultivar at Nambour is presented in Table I. Cv Bengal flowers and fruits about two to four weeks later than cv Tai So. Treatments on the same tree were cinctured at early, mid-, late and dormant flush compared with uncinctured branches. The cinctures were made in April (cv Tai So) and May (cv Bengal) with a hacksaw blade. For each cultivar, all treatments were applied within a fortnight and
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Effects of flowering of cjncturing litchi
the cinctured branches were 1.5 cm in diameter. A cut 4 mm wide and 4 mm deep was made in the branch to remove a layer of bark and cambium. Treatments on each branch were identified by coloured tags. In litchi the ratio of young to mature leaves on the terminal branch decreases as the flush develops. This is indicated by the increase in average leaf weight of the flush from early flush to dormant growth (Table II). The growth and flowering responses of the terminal branches were recorded at mid-panicle development (late July and early September for Tai So and Bengal, respectively). Data are the means of 9 Bengal and 10 Tai So trees with between 10 and 24 branches per treatment. The experimental design comprised two split plots (one for each cultivar), each tree being a main plot with the different cincturing treatments as sub-plots. Each cultivar was analysed separately. Daily maximum and minimum air temperatures, precipitation
and pan evaporation were monitored at the site (Table III). RESULTS
The non-cinctured branches of cv Bengal flushed during winter, while those of cv Tai So were dormant. Cincturing induced dormancy in all the branches, but the response in spring was influenced by both cultivar and flush stage (Table IV). In Bengal cincturing reduced flushing: this was associated with a strong increase in flowering when a dormant branch was treated, and a smaller increase with a branch in early or late flush. Flowering was not improved when the branch was in mid-flush. There was a tendency for young flushes to dessicate when the branch was cinctured. Flowering in the control branches was greater in Tai So than in Bengal and was not significantly improved by cincturing (Table IV). Cincturing the branch during early flush
TABLE I Stage of crop development in litchi at Nambour Stage 1. Vegetative flushing 2. Vegetative dormancy 3. Panicle differentiation (initiation 4. Panicle growth
emergence)
5. Flowering (anthesis, anther dehiscence and pollination) 6. Fruiting (fruit set - fruit maturity) a. Mainly skin, embryo and testa growth b. Cotyledons and beginning of aril growth c. Mainly aril growth 1 2
Time 2
Duration (weeks) 1 6-8 8-12 2-4 5-8 3-6
Jan.-Feb. Mar.-May May-June July-Aug. Aug.-Sept.
7-8 2-3 5-6
Oct.-Dec.
Duration of each stage varies with genotype and environment. For cv Tai So: cv Bengal is 2-4 weeks later.
TABLE II Effect of vegetative flush stage on average leaf dry weight (g per leaf) of Bengal and Tai So litchi. Data are averages of the top 6 leaves of 5 replicate terminal branches per treatment Cultivar
Flush stage Early flush
Mid-flush
Late flush
Dormant
0.35* 0.44
0.78 0.85
1.25 1.46
1.77 2.43
Bengal Tai So * LSD (P=0.05) = 0.26
TABLE III Climatic data during the experiment Parameter 0
Mean daily min. temperature ( C) Mean daily max. temperature ( C) Total monthly precipitation (mm) Total monthly pan evaporation (mm) 0
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
18.5 28.8 246 165
18.3 29.8 57 155
18.4 28.5 129 133
15.2 25.7 212 96
14.4 23.6 369 69
10.3 20.7 534 59
10.4 20.3 94 57
9.2 21.7 82 92
13.2 26.0 93 112
C. M. MENZEL and B. F. PAXTON TABLE IV Effect of cincturing at different stages of flush maturity on growth and flowering of Bengal and Tai So litchi. Data are the means of between 10 and 24 terminal branches each recorded at mid-panicle development (late July and early September for Tai So and Bengal, respective!ll_ Data on flowering have been transformed (inverse sin Vx+ 1). Means for each cultivar followed by different letters are significantly different (P = 0.05)
Response of terminal branches (%) Treatment Flushing
Dormant
Flowering
Cv Bengal Control Early flush Mid-flush Late flush Dormant
92.4 0.0 10.0 7.7 3.9
0.0 51.9 76.7 59.6 30.4
7.6a 48.lb 13.3a 32.7b 65.7b
Cv Tai So Control Early flush Mid-flush Late flush Dormant
15.8 35.3 25.9 20.8 7.7
0.0 0.0 3.4 2.2 0.0
84.2cb 64.5a 70.7ab 77.0cb 92.3cb
reduced flowering. This was associated with an increase in flushing. Seventy percent of the cinctures healed over by the time of flowering. There was no effect of cultivar or stage of cincturing on the rate of healing. Times to panicle emergence and flowering were increased and panicle and fruit size reduced compared to uncinctured controls when the cinctures were slow to heal. A few of the cinctured branches became chlorotic and sunburnt with dropped leaves, but none of them died (or were infected) during the experiment. Several of the cinctured branches produced a localized stem callus and swelling above the cincture. There was no noticeable effect of treatment on the relative degree of flushing (in flushing branches) in spring or the degree of flowering or fruit set (in flowering branches). Fruit number per panicle at maturity ranged from 0 to 10 and 1 to 39 in cvs Tai So and Bengal, respectively, but there was no consistent difference between treatments. DISCUSSION
This experiment confirms the observation that cincturing can promote flowering in litchi (Nakata, 1956; Young, 1977), but it also shows that the response is highly dependent on the physiological stage of the branch. In both cultivars, flowering in spring was significantly higher after cincturing a dormant branch com-
137
pared to cincturing during a period of flush development (Table IV). Cincturing only improved flowering in the more vigorous cv Bengal. There was no significant improvement in the flowering of Tai So. Cultivar differences have been reported elsewhere in litchi (Nakata, 1956; Paxton and Menzel, 1983) and in avocado (Lahav et al., 1971), mango (Mallik, 1951) and olive (Lavee et al., 1983). These results confirm previous observation that litchi trees that are about to flower well do not respond favourably to cincturing (Menzel and Paxton, 1986). Batten et al. (1982) suggested that cv Tai So was adapted to more tropical conditions (compared to Bengal) and our observations show that it initiates panicles under warm and wet conditions as at Nambour (Table II). The physiological mechanism by which cincturing promotes flowering in litchi is not well understood. While there seems to be no relationship between flowering and carbohydrate levels and the response to cincturing (Nakata and Suehisa, 1969), the role of phytohormones has not been investigated. Mustard (1954) suggested that floral initiation in litchi may depend on a balance between a growth promoter (flowering inhibitor) produced by young expanding leaves and a flowering substance (growth inhibitor) produced by mature leaves. It is possible that the response to cincturing at different stages of flush maturity simply reflects differences in the proportion of young and mature leaves on the terminal branches and consequently the relative accumulation of growth promoting and inhibiting substances above the cincture. The proportion of young to mature leaves on the branches decreased as the flushes matured (Table II). Dann et al. (1984) concluded that, in peach, cincturing altered the balance between endogenous growth substances which control the distribution of dry matter between vegetative and reproductive growth. Changes in stem growth could be measured with dendrometers on the limb within 24 h of cincturing. Starch and soluble sugars did not accumulate after cincturing. It is noteworthy that Loveys and Kriedemann (1974) showed an accumulation of abscisic acid above the cincture in grapevine. They did not record levels of carbohydrates. Some of the cinctured branches were slow to
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Effects of flowering of ci,ncturing litchi
heal and displayed a stem swelling, leaf drop, chlorosis and sunburn. This led to delayed flowering and fruit set and smaller fruit. Noel (1970) reported tree decline following cincturing was due to an accumulation of carbohydrates above the cut, poor callus differentiation, interference with water transport and reduced root development. Several techniques have been suggested for minimizing damage: smaller cinctures; cincturing alternate years; cincturing sections of a tree; covering the cincture with plastic; and the application of auxins and cytokinins (Nakata, 1956; Cohen, 1977; Lavee et al., 1983). Nakata (1956) provided some evidence that in litchi cincturing reduced the performance of non-cinctured sections of a tree. The yields of non-cinctured halves of trees were about 20% of the expected yield, when compared to noncinctured trees. This suggests it may be better to cincture in alternate years (rather than a percentage of the branches) as is the case in
the litchi industry in Thailand (Chapman, 1984). It is not known what proportion of the tree can be cinctured before the responses of the branches become affected. Lavee et al. (1983) showed that the response of different branches on an olive tree to cincturing were largely independent of each other. Up to 80% of the branches could be cinctured before yield was reduced. It is not unreasonable to suggest that the responses of the cinctured and uncinctured branches in the present experiment were independent of each other, since less than 10% of the terminal branches on an individual tree were cinctured. Further experiments are required before we can determine the relation between the proportion of branches cinctured and yield in litchi.
We would like to acknowledge M. Piccone for assistance with the collection of experimental data.
REFERENCES BATTEN, D. J., WATSON, B. J. and CHAPMAN, K. R. (1982). Urgent need to clarify and standardize variety names. Queensland Fruit and Vegetable News, 53, 890-4. CHAPMAN, K. R. (1984). Tropical fruit cultivar collecting in S.E. Asia and China. Queensland Department of Primary Industries. COHEN, A. (1977). Girdling effects on tree performance. Proceedings of the International Society of Citriculture, 1, 178-81. DANN, I. R., WILDES, R. A. and CHALMERS, D. J. (1984). Effects of limb girdling on growth and development of competing fruit and vegetative tissues of peach trees. Australian Journal of Plant Physiology, 11, 49-58. LAHAV, E., GEFEN, B. and ZAMET, D. (1971). The effect of girdling on the productivity of the avocado. Journal of the American Society for Horticultural Science, 96, 396-8. LAVEE, S., HASKAL, A. and BEN TAL, Y. (1983). Girdling olive trees, a partial solution to biennial bearing. I. Methods, timing and direct tree response. Journal of Horticultural Science, 58, 209-18. LovEYS, B. R. and KRIEDEMANN, P. E. (1974). Internal control of stomata! physiology and photosynthesis. I. Stomata! regulation and associated changes in endogenous levels of abscisic and phaseic acids. Australian Journal of Plant Physiology, 1, 407-15. MALLIK, P. C. (1951). Inducing flowering in mango by ringing the bark. Indian Journal of Horticulture, 8, 1-10. MENZEL, C. M. (1983). The control of.floral initiation in lychee: a review. Scientia Horticulturae, 21, 201-15. MENZEL, C. M. and PAXTON, B. F. (1986). Effect of cincturing of growth and flowering of lychee: preliminary observations in subtropical Queensland. Australian Journal of Experimental Agriculture, 26, (in press). NAKATA, S. (1953). Girdling as a means of inducing flower-bud initiation in litchi. Progress Note of the Hawaii Agricultural Experimental Station, 95, 1-4. NAKATA, S. (1956). Lychee flowering and girdling. Hawaii Farm Science, 4, 4-5.
C.
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and B. F.
PAXTON
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and SuEHISA, E. (1969). Growth and development of Litchi chinensis as affected by soil-moisture stress. American Journal of Botany, 56, 1121-6. NOEL, A. R. A. (1970). The girdled tree. Botanical Review, 36, 162-95. PAXTON, B. F. and MENZEL, C. M. (1983). Responses of lychee cultivars to cincturing. Research Report of the Maroochy Horticultural Research Station, 3, 60. YouNG, T. W. (1977). Effect of branch girdling on yield of severely pruned Brewster lychee trees. Proceedings of the Florida State Horticultural Society, 90, 251-3.
NAKATA, S.
(Accepted 23 July 1985)
