The Effect of Supplementary Pollination on Nut Set of Macadamia (Proteaceae)

The effects of supplementary pollination on initial and finalnut set and nut weight of theMacadamia cultivars, ‘HawaiiAgricultural Experiment Station 246’ and ‘HiddenValley A4’, were assessed over 3 years at an orchard ineastern Australia. The final nut sets of racemes bagged to excludeinsect pollinators were low in all 3 years of the study forboth cultivars. This demonstrated the importance of exposureto insect visitors to increase nut set of these cultivars. However,the improved initial nut set by supplementary cross pollinationof 246 in all 3 years of the study showed that insect pollinationis inefficient compared to hand pollination. Furthermore, supplementarycross pollination of 246 increased final nut set by 57–97%in 1989 and increased nut weight by 15.0% and kernel weightby 20.0% in 1991. Cross pollination of A4 did not result inany consistent pattern of initial nut set and did not improvefinal nut set, but increased nut weight by 11.6% and kernelweight by 18.4%, with a higher percentage kernel recovery in1991. In addition, supplementary self pollination of A4 increasednut sets in both 1989 and 1990. Yield and quality of both cultivarsmay benefit from increasing pollen transfer in the orchard. Macadamia integrifolia Maiden and Betche; Macadamia tetraphylla L. A. S. Johnson; macadamia; Proteaceae; cross pollination; self pollination; Apis mellifera ; Trigona ; nut set     

Pollen Tube Distribution in the Kiwifruit (Actinidia deliciosaA. Chev. C. F. Liang) Pistil in Relation to its Reproductive Process

High resolution light and fluorescence microscopy were usedto investigate the structural and cytochemical features of thekiwifruit(Actinidia deliciosa)pistil and to follow the pollentube pathway after pollination. The multicarpellary ovary issyncarpous only at the ovary level thus leaving 30–40free styles on top. The fusion of the longitudinally-foldedcarpels to form the syncarpous ovary forms a central parenchymatousaxis, the columella, from which the ovules radiate outwardsinto the ovary cavity. A prominent cup shaped depression onthe columella at the top end of the ovary, termed the pollentube distributor cup (PTDC) was detected. Pollen tubes fromthe stigma travel through the transmitting tract and enter thePTDC from where they are distributed towards the ovary. Evenwhen pollination is restricted to two stigmas, the PTDC seemsto ensure that the pollen tubes are evenly distributed aroundthe ovary resulting in an even distribution of seeds. This suggestedrole of the PTDC which could compensate for over and under pollinationof individual stigmatic arms is another adaptive feature whichplays a crucial role in the reproductive process of kiwifruit.The significance of this structure for pollination by insectsis discussed.Copyright 1998 Annals of Botany Company Actinidia deliciosa, kiwifruit, pollination, floral anatomy, reproductive success, pollen tube distribution.     

Periodicity of Pollen Development and Quantitative Cytochemistry of Exine and Intine Enzymes in the Grasses Lolium perenne L. and Phalaris tuberosa L.

Daily analysis of anther samples during flower development hasenabled an estimation of the duration of defined developmentalperiods in pollen of the grass Phalaris tuberosa. A similarsequence of pollen development has been established for ryegrass,Lolium perenne, where changes in activity of wall enzymes havebeen followed using quantitative cytochemical methods. Acidphosphatase, an intine enzyme, showed two periods of activity:during the vacuolate period corresponding to deposition of theintine polysaccharides; and in the maturation period correspondingto cytoplasmic activity. Non-specific esterase showed greatestactivity in the parietal tapetal cells until their dissolutionearly in the vacuolate period when an increase in pollen-associatedactivity occurred. These changes provide additional evidencefor the transfer of tapetal proteins to exine sites. Lolium perenne L., Phalaris tuberosa L., ryegrass, canary grass, pollen development, quantitative cytochemistry, enzyme activities, acid phosphatase, esterase     

Pollen--stigma Interactions: Development and Cytochemistry of Stigma Papillae and their Secretions in Annona squamosa L. (Annonaceae)

The development and cytochemical features of the stigma andstyle have been investigated in Sugar apple, Annona squamosaL., using light and electron microscopy. The pistil is a syncarpwith an open stylar canal. Papillae of epidermal origin lineboth the surface of the stigma and the inner face of the stylarcanal. The papillae contain organelles characteristic of secretorycells with a highly thickened cellulosic wall. The wall is multi-layered,the zones differing in their microfibrillar stacking and orientation.The stigma is of the ‘wet’ type and the surfaceexudate is heterogeneous in microscopic appearance and reactscytochemically for proteins, carbohydrates and lipids. The surfacecuticle undergoes dissolution prior to anthesis. A secretionalso appears in the thickened middle lamella of the sub-epidermalcell layer which reacts cytochemically for pectinaceous acidicpolysaccharides. Esterase activity of papillae is indicative of the receptiveareas, and it is also related to the onset of receptivity. Acidphosphatase activity is intense in the sub-epidermal cell layerswhich probably reflects their secretory activity. Pollinationtriggers a copious flow of secretion onto the stigma surfacewhich engulfs the pollen grains. It appears that most of theacidic polysaccharides of this secretion come from the middlelamella of the sub-epidermal cell layer. Compatible pollen tubes have no apparent barriers to overcomeon their route to the embryo sac and the inherent protogynousdichogamy seems to control the acceptance or rejection of compatiblepollen. Annona squamosa L., sugar apple, stigma, style, secretions     

Pollen Development and Quantitative Cytochemistry of Exine and Intine Enzymes in Sunflower, Helianthus annuus L

High resolution cytochemical methods have been used to characterizepollen development and pollen-wall structure in Helianthus annuus.Aniline-blue fluorescent material, presumably callose, was detectedin the nexine layer throughout its development. It was associatedwith acid phosphatase activity, while the outer sexine possessedintense esterase activity during the young spore period. Acidphosphatase and esterase were present in both intine and exinewall sites in contrast to their specific location in other pollentypes. Quantitative cytochemical estimates of enzyme activityduring development reveal esterase patterns typical of gametophyticsynthesis, while acid phosphatase patterns are characteristicof sporophytic origin suggesting tapetal transfer during thevacuolate period. Helianthus annuus L, sunflower, pollen development, exine enzymes, intine enzymes, quantitative cytochemistry