Development and Ultrastructure of Cucurbita pepo Nectaries of Male Flowers

The development of the nectary of the male flower ofCucurbitapepo L. was studied from 5d before to 2d after anthesis. Thenectary consists of parenchyma that stores starch in the presecretorystages, and epidermis. An hour before nectar secretion begins,the starch is hydrolyzed. The nectar exudes from the stomataand forms a continuous layer on the nectary surface. Duringanthesis the nectar may all be collected by pollinators or someor all of it may remain in the nectary and be successively resorbed.The nectary parenchyma stores material for synthesizing thesugar component of nectar and stores similar material againafter nectar resorption. It is also responsible for nectar productionand secretion. The epidermis is actively involved in the reabsorptionprocess. The resorption of nectar is a phenomenon that allowsthe plant to recover invested energy. Few observations on thisphenomenon have hitherto been published. Amyloplasts; Cucurbita pepo L.; courgette; nectaries; Nectar resorption; plastid; secretion; starch     

Structural and Cytochemical Characteristics of the Stigma and Style in Vitis vinifera L. var. Sangiovese (Vitaceae)

Studies were carried out on structural and cytochemical aspectsof the stigma and style ofVitis vinifera . The stigma is ofthe wet papillate type with a continuous cuticle and pellicle.During the development of the papillae, the cell walls increasein thickness and produce a secretion product constituted oflipids that pass through the wall forming the exudate. The styleis solid with a central core of transmitting tissue which hasconspicuous intercellular spaces that increase remarkably fromthe periphery to the centre where the cuticle is present. Theintercellular spaces, where the pollen tubes grow, contain amatrix that includes polysaccharides, pectic substances andscattered areas of lipidic nature. Cytochemistry; stigma; style; ultrastructure; Vitis vinifera     

Strip-shaped Projections at the Cytoplasmic Face of the Outer Membrane of the Generative Cell in Amaryllis belladonna

Strip-shaped projections are present at the cytoplasmic faceof the outer membrane of the generative cell in Amaryllis belladonna.This outer membrane is actually the inner plasma membrane ofthe vegetative cell which surrounds the generative cell. Theprojections are situated in groups and arranged parallel toeach other. Their predominant orientation is perpendicular tothe long axis of the generative cell. The projections are approximately35 nm high, and on average equally spaced 40 nm apart. Theirmaximum observed length, estimated from grazing sections ofgenerative cells, is 250 nm. Generative cell, outer membrane, Amaryllis belladonna, ultrastructure     

The Structure and Cytochemistry of the Pistil of Sternbergia lutea (Amaryllidaceae)

Studies were carried out on structural and cytochemical aspectsof the pistil of Sternbergia lutea (L.) KerGawl. The stigmais of the wet papillate type; the papillae are unicellular andare arranged densely around the rim of a funnel-shaped stigma.The stigma exudate is limited and is confined to the bases ofthe papillae and the inner lining of the stigma. The papillaeare smooth in the distal part and are covered with intact cuticle-pelliclelining. The cuticle is disrupted at places towards the baseof the papillae releasing the exudate. The exudate is rich inpectins and other polysaccharides but poor in proteins and lipids.The papillae show dense cytoplasmic profiles with extensiveendoplasmic reticulum (ER), abundant mitochondria, polyribosomesand active dictyosomes. The style is hollow. The stylar cavityis surrounded by two to four layers of glandular cells. In theyoung pistil the canal is lined with a continuous cuticle, butin the mature pistil the cuticle becomes disrupted and the canalis filled with the secretion produced by the cells of the surroundingglandular tissue. Ultrastructurally, the cells of the glandulartissue are very similar to the stigmatic papillae. The innertangential wall of the cells bordering the canal is uniformlythicker than other walls. The secretion in the stylar canal,as well as the intercellular spaces of the glandular tissue,stain intensely for pectins and polysaccharides but poorly forproteins and lipids. Pollen tubes grow through the stylar canal.Structural and cytochemical details of the pistil of Sternbergiaare compared with other hollow-styled systems. Pistil, Sternbergia lutea (L.) Ker-Gawl., stigma and style, structure and cytochemistry     

The Structure and Cytochemistry of the Stigma-style Complex ofCorylus avellanaL. 'Tonda Gentile delle Langhe' (Corylaceae)

Structural and cytochemical aspects of the stigma-style complexofCorylus avellanawere studied. In cross section the stigmaticstyle consists of papillae, one or two layers of sub-epidermalcells and a central transmitting tissue. The papillae coverthe style for about 80% of its length, are unicellular and arecoated with a cuticle-pellicle. During development, the cellwalls of the papillae increase in thickness and between them,below the cuticle, lipid bodies are observed. The sub-epidermalcells are similar in cell content to the papillae. The centraltransmitting tissue consists of highly vacuolated cells andthe intercellular spaces are filled with a proteic and polysaccharidicsubstance. Both the transverse and longitudinal walls containplasmodesmata.Copyright 1998 Annals of Botany Company cytochemistry, stigma and style, ultrastructure,Corylus avellana     

The Structure and Cytochemistry of the Pistil of Hypericum calycinum: The Stigma

The pistil of Hypericum calycinum has a pentacarpellary, syncarpousovary with five slender styles, each terminating in a smallstigma. The stigma is dry and papillate with a thin lining ofpellicle. The cuticle is thin and continuous around the papillae.A large vacuole filled with tannins occupies the major partof the papillae and the cytoplasm forms a thin lining aroundthe vacuole. The cell wall of the mature papillae show two distinctlayers - an outer layer of loosely woven fibrils and an innerdenser layer with compact fibrils. A large number of small lipoidalbodies accumulate just below the cuticle. The papillae havefewer organelles than those typical of glandular cells. Dictyosomesobserved occasionally are without associated vesicles. The cytoplasmis rich in ribosomes. The basal portions of the papillae mergeinto the transmitting tissue made up of loosely arranged cells.The intercellular matrix of the transmitting tissue is richin lipids. Pollen grains are deposited between the papillae.Upon pollen germination, pollen tubes enter the stigma throughthe interstices between the papillae Hypericum calycinum, cytochemistry, pistil, pollen-pistil interaction, stigma, ultrastructure