Podocarpus Species Research Articles

Chemistry of the Podocarpaceae. XXVIII. Constituents of some Podocarpus and other species

Chemistry of the Podocarpaceae. XXVIII. Constituents of some Podocarpus and other species

Chemistry of the Podocarpaceae. XXXIII. The structure of pododacric acid

Pododacric acid, a trihydroxy diterpenoid acid obtained from New Zealand Podocarpus species, has been formulated as 12,16,17- trihydroxyabieta-8,11,13-trien-19-oic acid (2) and its structure confirmed by partial synthesis from 12-hydroxypodocarpa-8,11,13-trien- 19-oic acid (1; podocarpic acid).

THE NODULAR MYCORRHIZAE OF PODOCARPUS ROSPIGLIOSII

Podocarpus is a genus of southern hemisphere and tropical conifers which are often important timber trees in their respective ranges. Nodular short‐roots were early noted as being similar in gross aspect to legume nodules, and it was inferred that they are Rhizobium‐bearing symbiotic structures which fix atmospheric nitrogen. In histological section the nodular short‐roots of the Venezuelan species Podocarpus rospigliosii were shown to contain endotrophic mycorrhizae. In a Koch's Postulates test, a fungus isolated from Podocarpus induced the formation of nodular structures on aseptic seedlings. A Nitrogen16 test was negative for fixation of atmospheric N2. Recent work in New Zealand has shown comparable histology in other species of the genus. The mycorrhizae may be important in forestry practice, though not as a source of nitrogen.

The Social Status of Agathis in a Rain Forest in Melanesia

Of the small group of conifers which occur in the lowland tropics species of Agathis, Dacrydium and Podocarpus grow mixed with angiosperms in tropical rain forest. Dacrydium and Podocarpus are predominantly montane genera with a few species descending into the lowlands, Agathis has rather more lowland species. In its present distribution (Florin 1963) and habitat Agathis is the most euthermic confer. Mixed conifer-angiosperm forests occur scattered through Malesiat and the southwest Pacific region. Their ecology has scarcely been investigated: this is important because of its bearing on the evolutionary history of the relationships between conifers and angiosperms. Further, tropical conifers, like temperate ones, are sometimes associated with podsolic soils and a study of them might be expected to throw light on the phenomenon of podsolization in the tropics. The temperate podocarp-angiosperm forests in New Zealand, and the forests of Queensland and New Guinea where species of Araucaria grow as emergents from an under-layer of Tropical Lowland and Lower Montane Rain Forest, have received some attention from ecologists. The native vegetation of much of the lowlands of New Zealand is a series of forests which range from pure angiosperm through angiosperm-podocarp mixture to pure podocarp. The main podocarp is Dacrydium cupressinum Soland. There are various hypotheses to explain this series, which Robbins (1962) has summarized. Cockayne considered that it represents an ecological succession, leading from conifer forest to angiosperm forest climax. Poole and Holloway later both suggested alternation of the forest types on any one site. Holloway later abandoned this explanation and suggested that a climatic change about 800 years ago had favoured the angiosperms and was leading to replacement of the conifers, still incomplete. Robbins himself postulated that there are two forest types, an ancient conifer forest and a geologically more recent angiosperm forest; both are found in pure form but in many places they have fused and the angiosperms are exercising a progressive supremacy over the conifers (Robbins 1962). Agathis australis Salisb. occurs in the north of New Zealand around Auckland. Apparently it does not regenerate in its own shade and in the climax vegetation is replaced by other species (Cockayne 1928, p. 127; Mirams 1957). According to Mirams (1957) it invades the secondary vegetation which springs up after clearing and at one stage in the secondary succession is well represented by all size classes; the big trees in

The mycorrhizal nodules of podocarps

Re-examination of the root nodules of New Zealand species of Dacrydium, Phyllocladus and Podocarpus and of Agathis australis (Araucariaceae) has confirmed that they are short roots upon which a new cortex is developed annually for several years. This cortex is normally occupied by phycomycetous mycelium, but this is not the cause of the nodules for in P. dactydioides they formed normally towards the close of the seedling's first year in fungus-free cultures. However, fungal infection is necessary to sustain growth in natural soils. Infected seedlings of P. totara attained a dry weight nearly seven times that of uninfected seedlings over 2 years; with P. dactydioides a fourfold difference developed in 1 year. The endophytic mycelium bore vesicles and arbuscles and made only transitory growth into agar. It appeared therefore to be the same as that forming mycorrhizas with most forest plants. The nodules are considered to be an adaptation to accommodate mycorrhizal fungi upon which growth normally depends, and thus to be functionally equivalent to the short roots of pines.

Part 3: The altitudinal gradient in forest composition, structure and regeneration

Abstract Changes in forest composition, structure and regeneration associated with increasing altitude from the eastern shore line of Secretary Island to tree line (2,950 ft) are described from a series of plots on a south-east aspect slope. Total and relative density values are presented for trees, small-trees, shrubs, herbs and regeneration categories of beech and podocarp species along the altitudinal gradient. Values are also presented for total and relative dominance (basal area) of the tree and small-tree layers, for canopy height and for stem size distribution of the important tree species along the gradient. Gradients in composition, structure and relative importance of species in the four strata are associated with increasing altitude, but rather abrupt changes in the tree, small-tree and shrub strata occur near the 1,500 ft contour. On this basis a lowland mixed forest and an upland beech forest can be distinguished. Among the 69 species listed in the four strata there is little indication that any are closely interdependent in distribution. The extensive overlap of altitudinal ranges is consistent with the individualistic concept of plant distribution. Because of the great variation in Fiordland forests, application of these results from undisturbed forest to other forests within the Fiordland region, may be rather limited.

Parasitic Conifer Found in New Caledonia

A rare and unusual species of Podocarpus from New Caledonia was collected and discovered to be parasitic on another conifer. The attachment is by modified roots imbedded between the cork cambium and the vascular cambium. A parasitic gymnosperm is something new to science.

A Taxonomic Revision of Podocarpus, XI the South Pacific Species of Section Podocarpus, Subsection B

A Taxonomic Revision of Podocarpus, XI the South Pacific Species of Section Podocarpus, Subsection B

A FLAT‐LEAVED PINE FROM ANNAM, INDOCHINA

American Journal of BotanyVolume 38, Issue 4 p. 245-252 Article A FLAT-LEAVED PINE FROM ANNAM, INDOCHINA J. T. Buchholz, J. T. Buchholz Department of Botany, University of Illinois, Urbana, IllinoisSearch for more papers by this author J. T. Buchholz, J. T. Buchholz Department of Botany, University of Illinois, Urbana, IllinoisSearch for more papers by this author First published: 01 April 1951 https://doi.org/10.1002/j.1537-2197.1951.tb14819.xCitations: 8AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume38, Issue4April 1951Pages 245-252 RelatedInformation

The Tertiary Fossil Conifers of South Chile and their Phytogeographical Significance, with a Review of the Fossil Conifers of Southern Lands

THIS seems the most striking of several war-time papers by Florin on the conifers. Here he describes three kinds of conifer shoots: two previously known as Sequoia are shown to agree in form and cuticle with living Podocarpus species (section Dacryocarpus) ; the third is a new genus, but probably a Podocarp. The Tertiary Fossil Conifers of South Chile and their Phytogeographical Significance, with a Review of the Fossil Conifers of Southern Lands By Rudolf Florin. (Kungl. Svenska Vetenskapsakademiens Handlingar, Serien 3, Band 19, No. 2.) Pp. 107 + 6 plates. (Stockholm: Almquist and Wiksells Boktryckeri A.-B., 1940.)

Embryogeny of Species of Podocarpus of the Subgenus Stachycarpus

1. Pronounced differences are found in the appearance and organization of the early embryos of Podocarpus spicatus, P. ferrugineus, and P. usambarensis, which belong to the subgenus Stachycarpus. 2. All three species have seven to twelve binucleate embryonic cell units. These units give rise to groups of cells which usually combined to form a single embryo; thus simple polyembryony prevails within this group. 3 The embryogeny of these three species suggests a sequence of evolutionary steps which appears to be opposite to the sequence suggested by study of the external morphology of the seed cone-the reduction series from a loose strobilus to a stalked ovule. Causal morphology may explain the modifications in the development of the embryo as due to changes in the shapes of the archegonia. 4. No apical initial cell could be observed at any stage in the development of the embryo of any of the species. 5. The resemblances between the embryos of Cephalotaxus and those of certain podocarps are superficial and d...

Maule Lignin Test on Podocarpus Wood

1. The Maule lignin test is apparently a reliable practical test for distinguishing the woods of the conifers from those of the angiosperms and the Gnetales. The only exception found was the single coniferous species Podocarpus amarus. 2. Xylem from the three types of Gnetales, Welwitschia, Gnetum, and Ephedra, all give positive Maule tests.

Vascular Anatomy of the Megasporophylls of Conifers

1. In the evolution of the ovulate strobilus in members of the Coniferales, two general tendencies are apparent: (1) the reduction in number of sporophylls in the strobilus; (2) the modification of a compound sporophyll into an apparently simple sporophyll; the latter appears in diverse disguises, but in general implies loss of one of the sporophyll members or welding of the two. 2. Strobilus reduction has reached its highest expression in members of the Cupressineae, Taxineae, and Podocarpineae; one type of strobilus reduction is represented by the general sterilization and reduction of parts in the lower sporophylls of Pinus. 3. Simplification of a compound sporophyll has been attained to fullest extent in Arthrotaxis selaginoides, Agathis, and Saxegothaea, and possibly others; an extensive reduction of bract occurs in Cedrus Libani and the lower sporophylls of Pinus maritima; the scale in Phyllocladus is probably reduced so as to be represented only by a distinct ovular supply; the welding of the two organs is complete in Juniperus communis and Chamaecyparis Lawsoniana. 4. Fusion of bract and scale vascular supplies does not directly parallel fusion of bract and scale. 5. Separate origin of bract and scale vascular supplies occurs most generally in the Podocarpineae and Abietineae; fusion of bract and scale supplies has reached its highest expression in the Araucarineae; both types of bundle origin are represented in the same strobilus in Cryptomeria japonica, Cupressus Benthamii, and the lower sporophylls of Pinus. 6. The bract bundle in plants with uninerved vegetative leaves divides only slightly if at all; the extent of the scale bundle system is directly related to the size of the organ supplied. 7. The scale bundles in the Abietineae and Chamaecyparis Lawsoniana form in the expanded portion of the organ a straight row or arc; in members of the Taxodineae and Cupressineae scale bundles swing around so as to lie at each side of the bract bundle. 8. In Cryptomeria japonica and Cupressus Benthamii and perhaps Cunninghamia Davidiana scale bundles accompany the bract bundle into the free portion of the bract. 9. A branching bundle in the vegetative leaf in Araucaria and Agathis probably implies a branching bundle in the bract of the sporophyll; the vascular system in the megasporophyll is probably a complex of bract and scale bundles. 10. In species of Podocarpus the scale bundles continue in the portion of the scale folded toward the dorsal side, forming the epimatium of the ovule.

The Staminate Cone and Male Gametophyte of Podocarpus

1. There are in the species of Podocarpus studied two prothallial cells which may or may not divide. There may be as many as eight prothallial cells in two tiers derived from the two primary ones. 2. Division in the prothallial tissue is mitotic and the prothallial cells do not degenerate. 3. There is a stalk cell and a body cell, sometimes differing very little from one another in appearance; whether both may produce male cells is yet uncertain. 4. The number of chromosomes is twelve and twenty-four. 5. There may be a variable number of cells or free nuclei in the pollen grain at the time it is shed.

The Microgametophyte of the Podocarpineae

1. The Podocarpineae as represented by the genera Podocarpus and Dacrydium are characterized by a proliferation of the two original prothallial cells through more or less numerous anticlinal divisions. 2. The anticlinal proliferation of the prothallial cells in some cases is accompanied by a similar proliferation of the generative cell, an abnormality which appears to have been described in no other Gymnosperms. 3. Similar proliferation of the two original prothallial cells has been observed in the araucarian genus Agathis. 4. The proliferation of the two prothallial cells in the Podocarpineae and Araucarineae and the proliferation of the generative cell in certain species of Podocarpus, cannot be regarded as primitive feature. 5. The ground plan of microgametophytic development found in the Podocarpineae and Araucarineae points to their derivation from an ancestral stock allied to the Abietineae. 6. Since the Podocarpineae and Araucarineae present many features of similarity in general habit, in geographical distribution, in the organization of their megasporophylls, and the development of their microgametophytes, it seems not improbable that they are somewhat more nearly allied than has been supposed.