The sepals of Hydrangea flowers which are pink during anthesis, afterwards turn green through the formation of chloroplasts. During this process the sepals grow to a considerable extent. From about 200 mm2 they expand to around 900 mm2. As a result of the greening process, the character of an insect-attracting flower organ changes into that of a foliage leaf. Parallel to this runs a change in anatomical pattern. The pattern changes of the lower epidermis were the object of special interest in the present investigation. Apart from the formation of new stomata during certain stages, disintegration of old stomata actually takes place. As far as the present authors are aware, no mention of this phenomenon is to be found in the literature. An excess of newly-formed stomata causes a considerable increase in the stomatal frequency and in the stomata index. A certain succession of processes involved in the change in anatomical pattern is discussed.

Acta botanica neerlandica

CC BY 3.0 NL ("Naamsvermelding")

Koninklijke Nederlandse Botanische Vereniging

T.W. Reyenga, & W.K.H. Karstens. (1964). Changes in the Epidermal Pattern of the Sepals of Hydrangea Macrophylla (Thunb.) D.C., “Otaksa” in their Successive Growth Phases. Formation of New Stomata, Disintegration of Old Stomata. Acta botanica neerlandica, 13(3), 340–351.