FLOWER DEVELOPMENT IN 'ALGERIE' LOQUAT UNDER SCANNING ELECTRON MICROSCOPY

Loquat (Eriobotrya japonica Lind.) blooms in late fall forming terminal panicles on shoots mostly formed during spring and after a period of summer rest. Macroscopic evaluations reveal that panicle formation initiates in Spain during September; however, flower induction and initiation are not, so far, properly dated. Modifications of the flowering dates require a deeper knowledge of the evolution taking place within the reproductive buds. With the aim to document the anatomical changes leading to the formation of the terminal panicles, a developmental study was initiated using scanning electron microscopy. Sequential sampling of terminal buds has revealed that the first indications of flower commitment in ‘Algerie’ loquat occur in late July. Trimerous structures corresponding to two different sized floral bracteoles and a centered flower dome were often seen the first week of August. Not until mid-August, the outermost flower whorl containing the sepals could be clearly recognized, 4 weeks before the large size of the apical buds reveals macroscopically their flowering condition. Sepals develop sequentially in a 3/5 pattern of phyllotaxy during August. Petals rose simultaneously alternating to sepals at the end of August. Stamens formation was initiated on Sept. 9, and anthers could be distinguished on Sept. 23. Gynoecium elevates forming five stigmas on mid-September, a week after stamens initiation. Two anatropous bitegmic and crassinucelate ovules per carpel could be seen developing below hypanthium at the end of September. Trees subjected to postharvest water stress initiate flower formation 3 weeks earlier. Water deficits extending beyond July likely affect flower quality and their reproductive potential.