Membrane localised gibberellins A₉ and A₄ in wheat chloroplasts

Abstract

GIBBERELLINS help to regulate plant growth and development, but their mechanism of action is still not clear¹. Attempts to correlate the levels of solvent-extractable gibberellins in plants with specific developmental events have shed little light on these problems. Turnover rate is one variable of possible physiological importance not accounted for when steady state levels of extractable hormone are measured. Another relevant factor is the way in which the hormones are sequestered or compartmented within the cell; this may reflect both how the hormone acts and is controlled and how it can be extracted. Prompted by recent evidence that gibberellins are released from wheat² and barley³ etioplasts in vitro by red light, we investigated whether gibberellins are associated with membranes in wheat chloroplasts. We found that gibberellins (principally GA₉ and GA₄) can be extracted from chloroplast membrane preparations using novel extraction procedures. Quantities found were much greater than the amounts of gibberellins previously extracted from the vegetative tissues of any plant species.