Studies on juvenility of mangosteen (Garcinia mangostana L.).

摘要

A study of juvenility in mangosteen (Garcinia mangostana L.) trees was undertaken in Thailand between 1995 and 1998. It was found that the growth rates of trees at the juvenile, near mature and mature phases were significantly different and could be used to distinguish the phase change of mangosteen. Tree age and canopy size were also characteristics associated with maturation, and that canopy size was more highly correlated with phase change than age. The phase change in mangosteen was associated with and possibly determined by the attainment of a minimum canopy size.; Maximal photosynthetic rate (P_{n (max)} ) was 8.52 μmol m−2 s−1 and light above 600 μmol m−2 s−1 of PPFD saturated the photosynthetic response of leaves exposed to full sun. Quantum efficiency was 0.03 mol mol−1. Leaves growing inside the canopy had increased size, dry weight and specific leaf area (decreased leaf thickness), and lower P_n rate than leaves exposed to full sun on the same tree. Stomatal conductance (g _s) at PPFD saturation point was about 390 mmol m−2 s−1.; The growth regulators, GA₄₊₇, BA, GA₄₊₇ + BA, and thiourea + dextrose and photoperiod extension treatments significantly accelerated growth of young mangosteen plants under nursery conditions and resulted in taller plants with greater total leaf area when compared to the untreated controls. Thiourea + dextrose and 2-hour-photoperiod extension treatments resulted in more growth than did other growth regulator and photoperiod treatments. After field transplanting, all treated trees increased their canopy size more rapidly than the untreated trees. With this accelerated rate of development, the treated trees might be able to attain the minimum size associated with maturation earlier than the controls.; Water stress and appropriate water management strategies after attaining a threshold stress condition were demonstrated as a suitable agro-management practice to induce flowering in mangosteen. Mangosteen trees subjected to the stress conditions that induced leaf water potential of −0.93 to −1.08 MPa followed by either 1.85 times the total daily evaporation every 3 rd day or by an initial application of 35 to 40 mm of water per tree and half of the initial rate applied at 7-day-intervals until flowering produced the largest amount of flowers and fruits.