Physiology of Post-Pollination Exudate Production in Acacia

Marginson, R., Sedgley, M. and Knox, R. B. 1985. Physiologyof post-pollination exudate production in Acacia—J. exp.Bot. 36: 1660–1668. Stigmas of A. wattsiana produced 1260 nl of secretion by 90min after pollination. The optimum temperature for post-pollinationsecretion in A. baileyana, A. brownii and A. iteaphylla was20°C. Both self and cross intraspecific, interspecific andintergeneric pollinations produced a similar positive responsein A. iteaphylla and A. baileyana. In all cases aged pollenwas as effective as fresh pollen despite reduced fluorescencein the fluorescein diacetate test. Live yeast cells, fixed chickenerythrocytes, glass beads, talc and Biogel P150 did not stimulatesecretion, nor did pollen which had been washed in water orethanol despite high retention of viability in some cases Pollendiffusates dried on to glass beads produced a positive responsein A. iteaphylla and A. gracifolia. Intraspecific and interspecificpollinations involving fresh Acacia pollen resulted in pollengermination on the stigma and pollen tube growth in the styleof A. iteaphylla and A. baileyana. In contrast washed pollenfailed to germinate and pollen germination and tube growth werereduced at 35 °C as compared with 20 °C. Key words: Acacia, pollination, secretion     

Effects of inter‐fire intervals on the reproductive output of resprouters and obligate seeders in the Proteaceae

Abstract Fire is often used as a management tool in fire‐prone communities to reduce fuel loads with the intention of reducing the severity and extent of unplanned fires, often resulting in the increased occurrence of fire in the dry sclerophyll vegetation of Australia. This study examined the effects of fire frequency (length of the inter‐fire interval) on the reproductive output of seven plant species in the Proteaceae, including obligate seeding shrubs (Hakea teretifolia, Petrophile pulchella), resprouting shrubs (Banksia spinulosa, Isopogon anemonifolius, Lambertia formosa) and resprouting trees (Banksia serrata, Xylomelum pyriforme). Reproductive output (measured as either number of confructescences or follicles) and relative size were estimated for 100 individuals at each of five sample sites, covering a range of past fire frequencies over 26 years including repeated short inter‐fire intervals. Patterns in reproductive output (after standardizing for size) were related to the life‐history attributes of the species. In areas that had experienced short inter‐fire intervals, obligate seeders had greater reproductive output compared with longer intervals, and the reproductive output of resprouting shrubs was less. Fire frequency did not affect reproductive output of the resprouting trees. The decreased reproductive output of the resprouting shrubs could be due to the allocation of resources to regrowth following fire rather than to reproduction. It is less clear what process resulted in the increased reproductive output of obligate seeders in high fire frequency areas, but it could be due to the most recent fires being more patchy in the areas experiencing shorter inter‐fire intervals, or it may have resulted from the selection for early reproduction in the high fire frequency areas. These results highlight the need to take into account past fire frequency at a site, in addition to time since the last fire, when planning prescribed fires.     

Cell Recognition: Antigenic Determinants of Plant Organs and Their Cultured Callus Cells

We present evidence that plant cells, like animal cells, may be typed according to their specific cellular determinants. Stems, leaves, pistils, and anthers of sweet cherry, Prunus avium , and their derived callus cells in culture have been examined by immunological methods to determine both to what extent parental characteristics are retained by the callus cells and the relationship between callifrom different organs. For the organs, some antigenic determinants were shared while others were unique to a particular organ. Callus cells derived from different organs share some common determinants, while others are specific. Although the callus cells from a particular organ retained their antigenic individuality, they also expressed a wider range of determinants than their parental tissues. Parental antigens were still expressed in callus cells after four subcultures. In suspension culturès of leaf and pistil callus, the organ-specific antigens were present in the culture filtrate and were associated with the protein rather than polysaccharide fractions.