Physiological and Biochemical Changes Accompanying Pollination in Orchid Flowers. Ii. Respiration, Catalase Activity, and Chemical Constituents

Abstract

In a previous paper of this series (19), data have been presented to show that pollination in orchid flowers brings about considerable changes in their water balance. The present paper deals with the change in respiratory activity, catalase activity, and chemical constituents as consequences of pollination and auxin treatment. The general methods used in sampling and treatment of flowers are essentially the same as that earlier described (19). A general conclusion, based on all experimental facts presented in both papers, is also given here.Respiration WHITE (35) noted an increase of respiratory rate and also of respiratory quotient after pollination in a number of plant species. A critical examination of her data, however, would seem to show that the respiratory quotient was unusually low for the non-pollinated plants, indicating that some constant errors might have been involved. Moreover, in most of the plants she used, fertilization is known to follow pollination more or less closely. It is therefore not safe to attribute the observed effects, if valid, to pollination alone. Further work is needed on the effect of pollination on respiration.In the work reported here respiration was measured as the amount of 02 taken up per unit of time per unit of dry weight. A Warburg respirometer of the constant volume type was employed. All experiments were run at 250 + 0.20 C.Preliminary study showed that when tissue sections were floated on phosphate buffer solution at a pH of 5.8 the liquid tended to enter the intercellular spaces and gave the tissues a translucent appearance. Therefore, the use of the buffer solution was omitted and the tissues were put directly into the flasks without any added liquid. Two tenths of a milliliter of 20% KOH on filter paper was used in the center well. After equilibration, readings were taken at 15-or 30-minute intervals until several constant values had been obtained. An average reading of four to six intervals was usually taken to represent the respiration value.The respiratory quotient was obtained by using the same sample in the same flask, instead of using two separate flasks. Readings were first taken without KOH in the center well; KOH was then added and readings were I Present address:

Carbohydrate Metabolism in the Tomato Fruit as Affected by Pollination, Fertilization and Application of Growth Regulators

“…These results are in good agreement with the analytical records for flowers, the naturally set young fruit of Pyrus malus (27), and the observations of carbohydrate changes after pollination or chemical treatment of orchids (12). Following pollination a rapid starch synthesis has been observed in ovaries of orchids (32) and ovaries of Aralia, Erodium and Pelargonium (14,16).…”

“…Marked changes in carbohydrate content in ovaries after pollination were observed in orclhids by HSIANG (12), and SESHAGIRAH (32) noted an increased starchl synthesis in the ovaries, receptacles, and pedicels immediately after fertilization which also has been pointed out as a common occurrence by IMARRE (16,19). The excision of young seeds usually leads to a reduction in starch and sugar content in associated tissues (17,19) with a corresponding increase in amylase activity.…”

“…In the case of the rapidly growing ovary, one would expect a decrease of the initial concentration as a consequence of water uptake during growth and metabolic utilization of carbohydrates for respiration, whichi is noticeably increased after pollination or auxin treatmiient (12,34,36,39), and for synthetic purposes. The fact that the opposite condition is found, i.e., carbohydrate concentration increases, slhows that in the developing ovary a powerful mechlanism is working to accelerate the rate of sugar intake in the growing cells.…”

The Biochemical Response of Electrical Signaling in the Reproductive System of Hibiscus Plants

“…The pollination-induced increase of respiration corresponds to previous studies in orchid flowers (Hsiang, 1951). Goh et al (1982) reported that much of the increase in Vanda flowers is centered in the placenta and exhibits three peaks, one of which occurs immediately after pollination.…”

Respiratory Metabolism in Isolated Orchid Petal Cells

“…Hew (1980) showed that carbohydrate metabolism in the mature orchid flower proceeded via the EMP pathway. A respiratory quotient of 1 has been observed for the column and perianth of Coelogyne mooreana, Cymbidium lowianum (Hsiang, 1951) and labellum of Oncidium goldiana (Hew, 1980). Whether or not changes occur in the respiratory pathway of orchid flowers during development remains unclear.…”