Improved microspore culture and doubled-haploid plant regeneration in the brown condiment mustard (Brassica juncea).

 The availability of doubled haploids could greatly contribute to improving seed quality in condiment mustard (Brassica juncea). We have developed an efficient and reliable protocol of microspore culture, modified from that of Baillie et al. (1992), based on a modification of the sucrose concentration of culture media.

Fertile pea plants regenerate from protoplasts when calluses have not undergone endoreduplication.

Large numbers of viable protoplasts were isolated and cultured from five pea genotypes. Calluses obtained (percent final plating efficiency (% FPE)=0.65-2.

Artefactual Origins of Cyclic AMP in Higher Plant Tissues.

A highly sensitive radioimmunoassay has been used to determine the levels of adenosine 3',5'-cyclic monophosphate (cAMP) in five higher plants (Lactuca sativa, Helianthus annuus, Oryza sativa, Pinus pinaster, Nicotiana tabacum). Particular attention was paid to the three main sources of errors in the characterization of cAMP in plants: presence of interfering substances in plant tissues; possible artefactual formation of cAMP from endogenous ATP during extraction, purification, and assay; and microbial origin of cAMP. In all the tested tissues, the cAMP level was below the detection limit of 0.

Critical oxygen pressure for growth and respiration of excised and intact roots.

A method based on the measurement of ATP/ADP ratios is described. It permits the determination of the critical respiratory oxygen pressure of any organ, or part of any organ, of an intact plant. The data obtained by this method with intact maize (Zea mays L.