Litchi chinensis Sonn.

Journal of Horticultural Science (1988) 63 (2) 349-360

Effect of temperature on growth and flowering of litchi (Litchi chinensis Sonn.) cultivars By C. M. MENZEL and D. R. SIMPSON Maroochy Horticultural Research Station, Queensland Department of Primary Industries, P.O. Box 5083, Sunshine Coast Mail Centre, Nambour, Queensland, Australia, 4560 SUMMARY

Moderate day/night temperatures (20°/15° v. 15/10°C) increased vegetative growth and reduced flowering in the seven litchi cvs Tai So, Bengal, Souey Tung, Kwai May Pink, Kwai May Red, Salathiel and Wai Chee. At higher temperatures (25/20° and 30/25°C), vegetative growth was promoted further and flowering eliminated. Temperature also influenced the type of inflorescence formed. More leaves were formed on the panicles of trees growing at 20/15° than at 15/10°C. All terminal shoots on all cultivars produced panicles at 15/10°C. The relative order for the amount of flowering at 20/15°C was: 'Wai Chee'>'Salathiel'>'Kwai May Pink'>'Tai So'>'Bengal'>'Souey Tung'>'Kwai May Red'. Cultivars which were vigorous at high temperatures produced fewer panicles at 20/15°C and fewer leafless panicles at 15/10°C. Only small differences were observed in the leaf water potential and the nutrient status of the shoots at different temperatures. Vigour and flowering of the cultivars in the glasshouse generally reflected field performance in subtropical Australia (Lat. 27°S). Low vigour could be useful for selecting litchi cultivars for good fruiting in environments with warm autumns and winters.

THE litchi (Litchi chinensis Sonn.) is one of the least adaptable of tropical and subtropical fruit crops, which flowers and fruits satisfactorily only in areas which consistently experience cool dry winters (Menzel, 1983). These conditions are essential for cropping'because litchi flowers are initiated only after a period of vegetative dormancy in the terminal shoots. Information relating growth, flowering and temperature in litchi ~has come from several sources: ecological studies associated with its origin in southern China and adaptation to the major production areas in the subtropics (Groff, 1943); correlations between the incidence of flowering and temperatures in the field (Young, 1970; Shukla and Bajpai, 1974) and more recently from the results of controlledtemperature experiments (Nakata and Watanabe, 1966; Batten and Lahav, 1981; Menzel and Paxton, 1985)~ From these studies it can be concluded that litchi trees require a period of low night temperatures (below 7 to 15°C) to flower adequately: Nakata and Watanabe (1966) showed in glasshouse experiments, that average daily

minimum temperatures of 13.9° compared to 20.8°C (with a common daily maximum between 21.1° and 32.3°C) increased the proportion of 'Tai So' litchi trees that flowered and the number of inflorescences per terminal shoot. Similarly, Batten and Lahav (1981) grew the three litchi cvs Kwai May, Haak Yip and Bengal in controlled temperature glasshouses maintained at constant temperatures between 10° and 35°C. The plants grew best vegetatively at 30°C, ceased growth below 15°, but flowered only at 10°C. Low temperatures ( 5 cm long with a Li-Cor leaf-area meter), number of lateral shoots per branch and dry weights of leaves and stems. A record was also kept of the times and numbers of vegetative flushes. Plants at 20/15° and 15/10°C were harvested at completion of flower anthesis. Plants which had not reached this stage after 18 weeks were transferred to a heated glasshouse (with a day temperature of 30°C falling to a minimum night temperature of 25°C) for 2 to 3 weeks before harvesting. In addition to vegetative characteristics, flowering plants were measured for the times of visible panicle emergence and 50% flower anthesis, number of panicles per tree, number of lateral branches per panicle, flower number per panicle and panicle length and dry weight. Observations were also made on floral biology and sex ratio. Vegetative and reproductive shoots were analysed for N, P, K, S, Ca, Mg, Fe, Zn, Mn, Cu, B, Na and Al content as previously described (Menzel et al., 1987). Data are the means of seven trees per treatment with cultivars randomized within each glasshouse. Most data have been transformed by inverse sin ( % flowering and % panicle weight distribution) or ln (y+ 1) transformation (stem and panicle extension, lateral number, leaf area and number and leaf and shoot dry weight) before ANOVA. Analysed cultivar means have been back-transformed for presentation in the tables. Temperature means are presented as transformed values±SE with equivalent means in parentheses. Most of the cultivars used in this study are of Chinese origin. The exceptions were 'Bengal' and 'Salathiel' which were developed in India/ Florida and Australia, respectively. Early plantings of lychee in Australia were based mainly on cvs Tai So and Bengal. More recently, plantings have been established with 'Kwai May Pink', 'Wai Chee', 'Salathiel' and, 'Souey Tung'. 'Kwai May Red' is rarely found ' outside arboreta. RESULTS

Most of the responses to temperature and

C.

M. MENZEL

and D. R.

cultivar were highly significant (P