Plasma-membrane dynamics in live protoplasts from maize (Zea mays L.) roots were characterized and examined for relationships as to the ability of the protoplasts to synthesize new cell walls and develop to cells capable of division. The lateral diffusion-coefficients and mobile fractions of fluorescence-labeled plasma-membrane proteins and lipids were measured by fluorescence photobleaching recovery. Small but significant effects on the diffusion of membrane proteins were observed after treatments with oryzalin or amiprophosmethyl, microtubule-disrupting drugs that increased the mobile fraction, and after treatments with cytochalasins B or D, microfilament-disrupting drugs that decreased the diffusion coefficient. A number of parameters were tested for correlative effects on membrane dynamics and protoplast performance in culture. Protoplasts isolated with a cellulase preparation from Trichoderma viride showed faster membrane-protein diffusion and a lower frequency of development to cells capable of division than did protoplasts isolated with a cellulase preparation from T. reesei. Membrane proteins in maize A632, a line less capable of plant regeneration from callus, diffused with a smaller diffusion coefficient but a greater mobile fraction than did membrane proteins in maize A634, a line with greater regeneration capacity. The plasma membranes of A632 and A634 protoplasts also differed with regard to lateral-diffusion characteristics of phospholipid and sterol probes, although the presence of both rapidly and slowly diffusing lipid components indicated the apparent existence of lipid domains in both A632 and A634. The protoplasts of the two lines did not differ significantly, however, in either wall regeneration or frequency of development to cells capable of division.

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Seedling populations of three cultivars of trifoliate orange [Poncirus trifoliata (L.) Raf.] were grown in a greenhouse from seed collected in three different years and four different locations. Starch gel electrophoresis of four heterozygous loci was used to distinguish nucellar (apomictic) seedlings from zygotic seedlings. Minimum estimates of the frequency of zygotics among 23 seed samples ranged from 0% to 76%, with an overall mean of 18%. All zygotics apparently originated from self-pollination or pollination by other trees of trifoliate orange. Samples collected from the same tree in different years had significantly different frequencies of zygotics. Differences among cultivars in frequency of zygotics were obscured by the large environmental effects. Samples stored for 8 months before planting generally did not differ in frequency of zygotics from those stored for 5 months. Mean height of zygotics was less than that of nucellars in all samples measured, significantly less in most samples. However, many zygotics were so similar to nucellars in height, leaf size, thorn length, petiole length, and stem diameter that they would be difficult to identify using these traits.