De-Ping Guo

Involvement of polyamines in cytoplasmic male sterility of stem mustard (Brassica juncea var. tsatsai)

Polyamines (free and conjugates) and the activities of enzymes, arginine decarboxylase (EC 4.1.1.19) and ornithine decarboxylase (EC 4.1.1.17), which are involved in the polyamine biosynthesis, were examined at different stages of flower development in floral organs of CMS and normal stem mustard (Brassica juncea var. tsatsai) in order to establish the correlation of polyamines with cytoplasmic male sterility. A lower total fresh weight of all floral organs, especially stamens, in cytoplasmic male sterile plants was observed compared to normal plants. Putrescine was the predominant polyamine in various floral organs of cytoplasmic male sterile and normal plants. During the flowering stage, all free polyamines and conjugates examined were present at a lower level in floral organs of cytoplasmic male sterile plants compared to normal plants. The activities of arginine decarboxylase and ornithine decarboxylase were higher in normal plants than in cytoplasmic male sterile plants, increasing steadily in the gynoecium and sepals during flowering, but declining in the stamen and during petal flower opening. The possible correlation between these results and cytoplasmic male sterility in stem mustard are discussed.

Stem swelling of stem mustard, as affected by temperature and growth regulators

Abstract Changes in the levels of zeation + zeatin ribosides (ZRs) and indole acetic acid (IAA) were determined in plants grown either in the greenhouse (25°C constant temperature) or in a tunnel (ambient temperature, 4–15°C) from the beginning of stem swelling until harvest. The plant fresh weight (FW) was lower at 25°C than at ambient temperature, stem swelling was almost completely suppressed and levels of ZRs and IAA were lower. Under ambient temperature, stem swelling occurred and ZRs and IAA levels were higher in both leaves and stem. At the end of the experiment, plants at high temperature had a long stem, tended to bolting, and the ratio of stem length to diameter was 4.1. Plants at ambient temperature formed a swollen stem, with a stem length diameter ratio of 0.8. Microcuttings were cultured in Murashige and Skoog (MS) media containing various concentrations (1–5 mg 1−1) of 6-benzylaminopurine (BA) and α-naphthaleneacetic acid (NAA). The stem diameter of microcuttings was significantly promoted by BA in the absence of NAA. Addition of NAA counteracted stimulatory effect of BA on stem diameter. NAA increased the stem length of microcuttings more than BA. The promotive effect of NAA on the stem length was counteracted by BA supplement to the medium.