HISTOLOGY OF PINUS-MAXIMINOI CONES INFECTED BY CRONARTIUM-CONIGENUM

Apparently healthy and C. conigenum infected female strobili of Pinus maximinoi, collected in Guatemala, were histopathologically studied by light microscopy. Scales from infected cones were fused and fertile s cales had aborted seeds. Infected cone scales lacked fibre cells in th e cortex, which are abundant in healthy cone scales. Intercellular spa ces of cortex contained abundant hyphae compared to phloem and xylem. The cell walls of infected tissues in the ovules were darkly stained, while those of comparable healthy tissue were colourless under Pianeze 's IIIB stain. Infected ovules of different developmental stages with nucellus, or nucellus plus spongy tissue, were observed. The cells of each tissue type contained many haustoria and did not develop into fem ale gametophyte and embryo. Ovule colonization by hyphae appeared afte r pollination and subsequently caused their early abortion.