POC Conf. Call 7-19-11

POC meeting, Webex Conference Call; Date: Tuesday July 19th, 2011 10am (PDT)

In attendance:

POC members: Absent:

Collaborators: none

Acceptance of the minutes from the POC_Conf._Call_7-12-11?

User requests, Plant Anatomy Ontology:

Legume terms submitted by Austin Mast

Remaining:

phyllode

Last week, we looked at examples of leaves where the petiole has phyllode development, but there is normal lamina development (with leaflets) beyond the petiole. We need a term to describe this, as well as when the whole leaf develops as a phyllode.

Background:

Boke 1940 (http://www.jstor.org/stable/2436690, DOI:10.2307/2436690) uses the term phyllode to refer only to those leaves without leaflets:

"The seedling usually displays 1 even-pinnate leaf, 1 bipinnate leaf, and several transition forms. Pinnate leaves and transition forms possess an apical pointlet like that of the phyllode."

The main reference people cite for phyllodes is: D.R. Kaplan 1980, Heteroblastic leaf development in Acacia: morphological and morphogenetic implications, La Cellule 73, pp. 137–203.

Kaplan say: "The present developmental comparisons between phyllodes and pinnatifid leaves in seedlings of Acacia have demonstrated unequivically that the blade of the phyllode is the longitudinal positional homologue of the lamina of the fully pinnate leaf, at all stages of development. At no stage is the phyllode blade merely a petiolar derivative, nor is there evidence of lamina suppression in favor of petiolar elaboration as suggested in the classical developmental paradigm."

Some more contemporary uses of the term phyllode:

Gardner et al. 2005 (http://www.publish.csiro.au/view/journals/dsp_journal_fulltext.cfm?nid=150&f=SB04052):

"A phyllode usually consists of a pulvinus and photosynthetic region, although it can be sessile, decurrent with the stem, or reduced to scales. The photosynthetic region is highly variable and ranges from vertically flattened, through terete, quadrangular and triquetrous to horizontally flattened. Phyllodes usually possess at least one extra-floral nectary on the adaxial nerve, and sometimes up to five. Boughton (1981, 1985) observed three types of extra-floral nectaries. She also investigated the indumentum and found almost all species have two kinds of trichomes, one glandular and one non-glandular (Boughton 1989). According to Arber (1918), the chief anatomical feature by which phyllodes differ from true leaf laminae is the occurrence of two opposing series of vascular bundles."

and later in the paper:

"Previous approaches, such as basic anatomy and inferences from the sequence of heteroblastic leaf development in acacias, have led researchers to state that the phyllode is homologous with the petiole of a bipinnate leaf (e.g. Mann 1894; Goebel 1905; Troll 1939), or with the petiole and rachis (e.g. Bentham 1875; Reinke 1897), and make comparisons with the monocotyledonous leaf. Investigating the developmental morphology of phyllodes, Kaplan (1980) proposed a new model: that the phyllode is actually the positional homologue of the lamina of a bipinnate leaf. In essence, this suggests that the phyllode is directly comparable to a simple leaf. Kaplan’s theory does not, however, address the issue of the opposing vascular bundles found in phyllodes.

"The pattern of branching observed in the vascular bundles of A. verniciflua phyllodes suggests that the abaxial marginal nerve is homologous to the mid-rib in a simple leaf. This implies that laminar expansion occurs on both sides of the ‘mid-rib’, but vertically, and fused together. The emergence of the adaxial marginal nerve as two separate bundles, originating on opposing sides that eventually fuse rather than directly from the vascular ring found in the pulvinus, supports our interpretation and has been observed (together with other patterns) in several other Acacia species (von Wartburg 1991)."

Leroy and Heuret 2007 (doi:10.1016/j.crvi.2007.11.006): "The subgenera Phyllodineae... as the species are characterised by a polymorphism of vegetative characters where bi-pinnate leaves are replaced by a type of foliar organ called a phyllode." and "...the different transitional forms range from pinnate leaves to phyllodes..."

See fig. 1 in this paper. They refer a "flattened petiole" and a "flattened rachis" in transitional leaves.

Yang et al. 2008 (DOI: 10.1007/s11240-008-9424-7) use leaf as synonym for phyllode in Acacia. Refer specifically to phyllodes without any pinnate (sic) on top of them.

Forster and Bonser 2009, Annals of Botany, use the term phyllode to refer to adult leaves without leaflets: "Acacia implexa (Mimosaceae) is a heteroblastic species that develops compound (juvenile), transitional and phyllode (adult) leaves that differ dramatically in form and function."

RW did not find any contemporary papers that said that a phyllode is a petiole.

Leaves that have phyllode-type development toward the base with leaflet development toward the tip are a type of transition leaf.

Proposed terms and definitions:

phyllode: An adult vascular leaf in which the laminar development is a median plane (perpendicular to the axis), rather than the more common state of in a transverse plane (tangent to the axis). (ref: Lawrence)

Comment: Common in legumes of the genus Acacia. Lamina development in a phyllode occurs from activity of the abaxial meristem early in development, similar to unifacial leaves. Similar development occurs in some monocot leaves, but they are not called phyllodes. Transitional leaves also occur, in which the basal portion of the leaf develops similar to a phyllode, but the apical portion of the leaf develops normal leaflets (see PO:xxxxxxx, transitional phyllode-type leaf). In some leaves, the petiole may twist giving the appearance that the lamina is a phyllode, but it is not. Phyllodes are generally xeromorphic.

is_a vascular leaf, is_a adult leaf

Unifacial leaf as synonym? No- not the same, but similar development. See Kaplan 1970 (http://www.jstor.org/stable/2485311). Might be better to make a parent term "ensiform leaf" which has children phyllode and unifacial leaf.

phyllode-type transition leaf: A transitional vascular leaf in which the basal portion of the leaf has lamina development similar to a phyllode, and the apical portion of the leaf develops leaflets similar to a juvenile leaf.

Comment: Common in seedlings of legumes of the genus Acacia.

bristle

More complicated, because it is a phenotype term, and applies to structures other than stipules.

Will discuss at a future meeting.

User requests: PGDSO:

Maize GDB

coleoptile emergence -- definition

From Mary at MaizeGDB: It would be more useful for maize if the definition for coleoptile emergence PO:0007045 were altered to be: Emergence of coleoptile from the seed (rather than above ground) . This could compare well to the radicle definition (PO:0007015 radicle emergence): The stage at which the radicle or root emerges from seed.

PO:0007045 cotyledon emergence is_a shoot emergence, and shoot emergence(PO:0007030) is defined as "Shoot or leaf breaks through soil surface."

All of the sibling terms to cotyledon emergence (coleoptile, epidcotyl, and hypocotyl emergence) are also defined as when they break through the soil surface, so if we change one, we should change all of them.

Do we all agree that it is better to define terms relative to other plant structures instead of to the environment?

PJ suggested that we don't need to obsolete and replace the terms, but RW feels that this is exactly the kind of change in definition that warrants obsoleteling the term and creating a new one.

Adding the replaced_by link would make moving existing annotations straightforward. There are 133 annotations on shoot emergence, including 1 from coleoptile emergence and 2 from cotyledon emergence.

Also, all of these terms should be renamed as stages or phases rather than as developmental processes - so, for example, PO:0007045 should be called coleoptile emergence stage, rather than coleoptile emergence. The definitions should reflect the fact that they are stages, not processes.

Furthermore, shoot emergence is part_of seedling growth, but has no is_a parent, and seedling growth has no is_a parent. We should fix these while we're redefining the terms.

current structure:

current: seedling growth: Growth of embryo after imbibition up to the development of the first adult leaves. part_of germination

Seedling growth stage should probably begin after germination, not after imbibition.

proposed: A vegetative growth phase that begins with germination and ends with the development of the first adult leaves.

Comment: This terms is used only for seed plants, although non-seed plants may have a comparable phase during which they produce juvenile or transition leaves.

current: shoot emergence: Shoot or leaf breaks through the soil surface.

proposed: shoot emergence phase: A vegetative growth phase that occurs when a shoot system emerges from a seed.

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