Morphological and structural changes during female cone development in Cunninghamia lanceolata

We selected Chinese fir (Cunninghamia lanceolata(Lamb.) Hook.) trees from Fuzhou,China,as experimental materials and performed a systematic study of ovulate strobilus development based on morphological and anatomical observations using a digital camera,stereoscopy,semi-thin sections,and scanning electron microscopy.Green ovulate strobili formed from late October to early November.They matured in mid-March of the following year,and then entered the pollination period.During this period,the female cones underwent several changes,including a color change (to yellow),size increase,and bract opening.During ovule development,the ovular primordia formed in early January,after which the integument and nucellus arose in late January.In late February,ovules formed,and a pollen chamber developed above the elliptic nucellus.During this period,integument tissue proliferated continuously to form a micropylar canal by surrounding the nucellus.In early March,the ovules continued to increase in size and the micropyle formed.Meanwhile,the size of the opening in the micropyle increased to a maximum.In mid-to-late March,the ovules began to secrete pollination drops above the micropyle.Subsequently,the drops disappeared and the tissue above the micropyle stopped growing.These results indicate that the ovulate strobilus of Chinese fir takes about five months from differentiation to maturity,and the morphological and structural ovule adaptations to anemophily are presumably due to long-term evolution.