SOME ASPECTS OF THE ECOPHYSIOLOGY OF FLOWERING INTENSITY OF MANGO (MANGIFERA-INDICA L.) CV NAM-DOK-MAI IN A SEMI-TROPICAL MONSOON ASIAN CLIMATE

During the dormant period in 1988-1989, four-year-old mango trees cv. Nam Dok Mai, grown in the orchard of the Department of Horticulture at Kasetsart University (Kamphaengsaen Campus), Nakhon Fathom Province, Thailand, were studied. The changes and relationships between leaf xyl em water potential (psi(x)), relative water content (RWC), total nonst ructural carbohydrates (TNC) in terminal shoots, and GA(3)- and ABA-li ke substances in shoot tips during November and December, and flowerin g were studied. Changes in psi(x) and RWC were from -0.31 MPa and 97% at the beginning of the dry period (mid November) to -0.82 Mpa and 93% , respectively in mid December. There was a positive correlation betwe en psi(x) and RWC. Low TNC levels were ca 70-98 mg glocose equivalent/ g dry wt.) at the beginning of the dormant period and thereafter incre ased to 110-120 mg glucose equivalent/g dry wt. and finally declined t o ca 70 mg glucose equivalent/g dry wt. prior to flowering. TNC were p oorly correlated negatively with RWC, but not correlated with psi(x). GA(3)-like substances were high (1.5-1.7 mu g equivalent/g fresh wt.) at the beginning of the dormant period, but declined by about 50% in l ate November prior to increasing slightly through to inflorescence eme rgence. The change in ABA-like substances was comparatively small duri ng the dormant period. GA(3)-like substances were negatively correlate d with RWC and psi(x) whereas ABA-Like substances were not. Flowering intensity was negatively correlated with average RWC and average psi(x ) (r = -0 65 and -0.72*, respectively) but was positively correlated with TNC (r=0.75*). Flowering intensity was negatively correlated wit h GA(3)-like substances (r= -0.79*), but not correlated with ABA-like substances. (C) 1997 Elsevier Science B.V.