S. Maldonado et M. Otegui, SECRETORY-TISSUES OF THE FLOWER OF SANANGO-RACEMOSUM (GESNERIACEAE) -I - LIGHT-MICROSCOPY, Acta botanica neerlandica, 46(4), 1997, pp. 413-420
Sanango racemosum (Ruiz & Pav.) Barringer has a dry stigma without a f
ree-flowing secretion fluid but with a hydrated proteinaceous pellicle
. The stigmatic surface is covered with unicellular, bottle-shaped pap
illae. At maturity, a viscous emulsion is accumulated between the cuti
cle and the pecto-cellulosic wall of the papillae, causing it to becom
e detached from the surface of the papilla cell walls, The style has a
central solid core of transmitting tissue. The cells of the transmitt
ing tissue are rich in starch and exhibit thick lateral walls rich in
pectic substance. The nectary disk is a ring elongated into a cup, wit
h five lobes at the top, One of the most conspicuous histological feat
ures of the disk is the abundance of starch in the secretory cells. Th
e disk is supplied only by phloem; the stomata are found in the top of
the lobes. A fluid substance is produced just before anthesis and sec
reted through the stomata with no visible decline in starch level. Dur
ing anthesis and after fertilization, a rapid decline in starch is obs
erved. The hypothesis that the disk has other functions besides that o
f a nectary is discussed.