A Histochemical Study of Embryo Sac Development inVanda(Orchidaceae)

Histochemical studies on the female gametophyte of Argemone mexicana L.

“…The presence of high concentration of RNA and total proteins in the synergids of Argemone mexicana (present observations) as also in Nicotiana synergids (Bannikova 1971) points out the fact that the cells are metabolically active and contribute by way of synthesis at the time of fertilization. This is in agreement with Alvarez and Sagawa (1965) who reported a similar nature of the synergids in Vanda. Although starch grains are absent within the synergids, small grains are seen in the adjacent nucellar tissue.…”

“…Similarly, Pritchard (1964), recorded a rapid synthesis of RNA by the functional megaspore in Stellaria media. An increased rate of synthesis of RNA and proteins in the functional megaspore have also been observed by Prasad (1977) in Farsetia hamiltonii and Eruca sativa and Alvarez and Sagawa (1965) in Vanda. Non functional megaspores are characterized by a very intense colouration for all the active substances localized (present observations).…”

“…The filiform apparatus in Vanda is also highly PAS positive (Alvarez and Sagawa 1965). The staining intensity decreases towards the basal region of the synergids.…”

“…Since the meiocyte is undergoing a premeiotic differentiation, an increased rate of utilization of meta bolites is to be expected. The rate of dilution of metabolites in the growing megaspore mother cell is attributed to the lack of synthesis at a rate sufficient to maintain its previous concentration (Alvarez and Sagawa 1965), the view to which we also subscribe. Heslop-Harrison (1972) described a temporary suspension of RNA synthesis in the rneiocyte.…”

A Cytochemical Study of Ovule Development in <i>Dipcadi montanum</i> Dalz

“…In D. montanum, the synergid nuclei are very faintly azur A positive while the filiform apparatus is densely PAS positive. The ultra-structural studies on cotton (Jensen 1965), Capsella (Schulz and Jensen 1968) and the histochemical studies on Stellaria (Pritchard 1964) and Vanda (Alvarez and Sagawa 1965) have revealed that the synergids play an important role in the synthesis of RNA and proteins and also in the transport and storage of histochemical substances obtained from the nucellus. With less DNA in the nuclei and with less RNA in the cytoplasm, the synergids seem to be not very active in D. montanum; anyhow, with rich proteins in them, their role as reservoirs of proteins can unequivocally be inferred.…”