Early Lignotuber Formation in Banksia—Investigations into the Anatomy of the Cotyledonary Node of TwoBanksia (Proteaceae) Species

Abstract

Anatomical descriptions are made of the cotyledonary node region of seedlings of B. menziesii R. Brown (1830) and B. serrata Linnaeus f. (1782), including information on node anatomy, bud type, location and number. Seedlings were sampled at 8, 15 and 26 weeks after seed sowing and observations made of serial transverse sections through the node region. In B. menziesii, fused auricles in combination with bases of the cotyledons form a thick sheath of parenchymatous tissue surrounding the base of the seedling stem. Three types of buds are present: (1) an exogenous axillary bud in the axil of each cotyledon and leaf; (2) endogenous accessory buds in the cortical tissue at the base of each cotyledonary axillary bud; and (3) exogenous adventitious buds generated serially along the line of fusion of opposing auricles which occur either side of the stem. Additional adventitious buds occur singly on the adaxial wall of the sheath. At 26 weeks, phenolic compounds such as tannins accumulate in the sheath, which later develops into a ligni®ed protective encasement in B. menziesii. Early cotyledonary node anatomy of B. serrata diers from that of B. menziesii, the fusion line of the auricles curving away and downwards from the stem base, thus precluding the formation of a sheath. Also, accessory buds are absent from the basal tissue of the cotyledonary axillary buds. Only two types of buds are present: (1) an exogenous axillary bud in the cotyledon and leaf axils and (2) exogenous adventitious buds generated along the line of fusion of opposing pairs of auricles, as well as from tissues next to each cotyledonary axillary bud. Knowledge of the number, types and location of buds present in the cotyledonary node will establish a base for further comparative anatomical studies and research on clonal cultivar development of Banksia.# 2000 Annals of Botany Company

CAN GENETIC VARIATIONS IN THE DEPLETION PROCESS OF STARCH STOCKS BE DRIVING CONTEMPORARY MICROEVOLUTION IN Toona ciliata VAR. australis?

“…It is beneficial for plants to have this structure mainly when they deal with strong environmental stresses (KERR, 1925;MIBUS, SEDGLEY, 2000).…”

“…To validate the use of neutral red for scoring radial parenchyma cells with remaining starch stocks as well as the adjustments of the starch depletion curves (TPC) for clone BV1120 model, we used 15 seedlings (three replicates and five times) of Eucalyptus urophylla which contained lignotubers at the same age and silvicultural treatments of T. ciliata seedlings, and we established a heat treatment of 55°C, at 0, 20, 40, 60 and 80 min time periods in the area of lignotubers (generally closer to plant collars), as these plant structures have a high content of starch stocks and they serve as protection of plants against biotic stresses, mainly due to high temperatures, for example, over forest fire regimes (KERR, 1925;MIBUS;SEDGLEY, 2000).…”

Lignotubers in Mediterranean basin plants

“…Lignotuber buds initially appear in the cotyledonary region (sometimes also at the first few leaf nodes) just a few months after germination (Kerr 1925;Chattaway 1958;Carr et al 1983;Molinas and Verdaguer 1993a;Graham et al 1998;del Tredici 1999;Mibus and Sedgley 2000). The buds progressively proliferate and arrange in clusters; they become very abundant (even in the order of thousands) in more advanced developmental stages (Wildy and Pate 2002).…”

“…The buds progressively proliferate and arrange in clusters; they become very abundant (even in the order of thousands) in more advanced developmental stages (Wildy and Pate 2002). In early lignotubers, buds are protected by a tanniniferous parenchymatic tissue in some Eucalyptus species (Chattaway 1958), by tannin-rich hypertrophied scales in Quercus suber (Molinas and Verdaguer 1993a), or by the extended base of the cotyledons (also tannin rich) in Banksia (Mibus and Sedgley 2000). In Eucalyptus and Banksia, these buds are enfolded by further development of the lignotuber that becomes macroscopically evident as a swelling at the cotyledonary node (Chattaway 1958;Graham et al 1998;Mibus and Sedgley 2000).…”

“…In early lignotubers, buds are protected by a tanniniferous parenchymatic tissue in some Eucalyptus species (Chattaway 1958), by tannin-rich hypertrophied scales in Quercus suber (Molinas and Verdaguer 1993a), or by the extended base of the cotyledons (also tannin rich) in Banksia (Mibus and Sedgley 2000). In Eucalyptus and Banksia, these buds are enfolded by further development of the lignotuber that becomes macroscopically evident as a swelling at the cotyledonary node (Chattaway 1958;Graham et al 1998;Mibus and Sedgley 2000). This swelling is not apparent in Q. suber seedlings; instead, this species shows an elongated hypocotyl with abundant cluster buds enfolded by hypertrophied scales, most of which are below ground (Molinas and Verdaguer 1993a).…”