Characteristics of Acacia mangium shoot apical meristems in natural and in vitro conditions in relation to heteroblasty

PDF version of the authors can be published in January 2013International audienceMorphological and histocytological characteristics of Acacia mangium shoot apical meristems (SAMs) were assessed in natural and in vitro conditions in relation to heteroblasty. In the natural environment, SAMs with a mature-phyllode morphology were much bigger, contained more cells with larger vacuolated area, or vacuome, and lower nucleoplasmic ratios than those from the juvenile type (Juv). In these latter, nuclei appeared more voluminous, evenly and lightly stained, with clearly distinguishable nucleolei and less abundant chromocenters. In vitro, where reversions from mature to juvenile morphological traits do occur unpredictably, heteroblasty was less obvious in the SAM characteristics examined. In vitro SAMs corresponding to the juvenile and mature types showed similarities with outdoor Juv SAMs, but could be distinguished from these latter by a much larger vacuome that might be induced by the culture conditions. These findings encourage pursuing the investigations at the chromatin and nucleolus level in SAM zones where heteroblasty-related differences have been detected

Chirosia betuleti (Ringdahl) (Diptera: Anthomyiidae) a gall-former on the ostrich fern, Matteuccia struthiopteris, with notes on other insect-fern associates

Volume: 89Start Page: 532End Page: 54

Identification of two thaumatin-like proteins (TLPs) in the pollination drop of hybrid yew that may play a role in pathogen defence during pollen collection.

We describe the proteomic identification of two pathogenesis-related group 5 (PR-5) proteins, an acidic thaumatin-like protein (TLP) and a basic TLP isolated from the pollination drop of hybrid yew (Taxus x media Rehder). The basic TLP (TxmTLPb) was the most abundant protein in the yew pollination drop based on protein spot size after two-dimensional electrophoresis. The acidic TLP (TxmTLPa) is also a major protein component of the yew ovular secretion and appears to be encoded by a number of mRNAs transcribed from a TLP gene family that has undergone limited sequence divergence. We have sequenced five acidic TLP-encoding cDNAs (TxmTLPa-1,2,3,4 and 5) isolated from the yew ovule that vary from each other by no more than five out of 233 amino acid residues in their predicted protein sequences. All of the cDNA variants encode TLPs possessing the 16 conserved cysteine residues and five charged amino acid side chains associated with antifungal activity. Amplification of genomic DNA with TxmTLPa primers indicated that at least 11 acidic TLPs with highly similar amino acid sequences may be expressed in yew tissues. Antibodies against TLPs confirmed the identity of TxmTLPa and TxmTLPb in the yew pollination drop and detected TLPs in the ovular secretions of four other species from three other conifer families. Our results suggest that TLPs are a conserved component of conifer ovular secretions and are involved in broad spectrum pathogen defence of ovules.Peer reviewed: YesNRC publication: Ye

Sugary Exudates in Plant Pollination

Sugary secretions are present in many plants and frequently they are linked with reproductive processes. Most of the gymnosperms, both extant and extinct, possess a pollination drop, a diluted sugary secretion protruding from the micropyle, which serves for pollen capture, hydration, and transport in the ovule. It is most probable that this secretion attracted insects giving origin to a plant–insect relationship for pollination based on a sugary solution well before the raise of angiosperm. Floral nectar, a new type of sugary exudate produced by a specific secreting tissue (the nectary), evolved rapidly when the transition from naked ovule to closed carpel was completed and the pollination drops were no longer available as a food resource for insects. Floral nectar is widely distributed and very diverse in the extant angiosperms where it represents the more common reward for a large variety of pollinators. In this chapter, we highlight the evolutionary relationship between nectar and pollination drops in terms of morphology, physiology, ecology, and biochemistry

Effects of endogenous ABA levels and temperature on cedar (Cedrus libani Loudon) bud dormancy in vitro

2 illus. 2 tables 1 graph.International audienc