A new species of Amentotaxus (Taxaceae) from China, Vietnam, and Laos

A new species Amentotaxus hekouensis L.M. Gao is described as new to science from Hekou, Yunnan of China, Lao Cai of Vietnam and Xiang Khouang of Laos. The new species is similar to A. argotaenia (Hance) Pilg. in linear or linear-lanceolate leaves, stomatal bands white and microsporophylls 6–8, each with 4–6 pollen sacs, but differs from the latter by its larger leaf size with 8–12.5 cm × 0.9–1.4 cm (vs. 2–11 cm × 0.5–1.1 cm in A. argotaenia), long acuminate leaf apex (vs. rounded to sharply triangular in A. argotaenia), stomatal bands with 25–30 rows (vs. 15–25 rows in A. argotaenia), stomatal bands equal to or slightly narrower than marginal bands (vs. narrower than marginal bands in A. argotaenia); pollen-cone racemes borne 1–2 (vs. 2–4 (10) in A. argotaenia), cones in 12–16 pairs (vs. ca. 12 pairs in A. argotaenia). Its distinctive nature has also been confirmed through DNA barcoding analysis of this genus. The new species is provisionally assessed as endangered (EN) due to its restricted distribution, small population size and the prevalence of habitat destruction within its range.

Thermogenesis and developmental progression of Macrozamia macleayi pollen cones

Macrozamia macleayi Miq. (family Zamiaceae) pollen cones generate high thermogenic temperatures that are crucial to pollination of these dioecious plants. However, cone thermal behaviour has not been characterised with respect to developmental stage, so any links with the progression and development of their pollination processes remain unclear. Here we show that after growing to full girth, cones progress through thermally active stages of slow/no growth, rapid lengthening, dehiscence and early post-dehiscence, each with a distinct thermal response. During slow/no growth cones exhibit a small late afternoon peak thermogenic temperature elevation above peak ambient, and remain elevated overnight. During rapid lengthening the late afternoon/night-time temperature elevations disappear, and mid-day thermogenesis commences. During dehiscence the midday cone temperature elevations become large, approaching 10°C near the day of maximum dehiscence rate, and then decrease daily. Pollen cones generate their large, dehiscence stage thermogenic temperature elevations synchronously with the diel ambient temperature peak, thus maximising the peak cone temperature. This likely enhances the expulsion of their pollen bearing obligate mutualist thrips pollinator, thus boosting pollination rates. Thermogenic events are fuelled by carbohydrates only, and significantly increase the pollen cone water loss – yet the percentage of water in sporophylls remains nearly constant (~63%) throughout all developmental stages. Similar coordinated pollen cone developmental stage and thermogenic responses are also present in Cycas micronesica K.D. Hill (family Cycadaceae), suggesting a conserved physiological response across cycad families.

Leafy shoots and pollen cones of conifers from the Middle Jurassic deposits of the Irkutsk Coal Basin

Among the numerous remains of the Jurassic conifers in the Irkutsk Coal Basin, several types of leafy shoots are distinguished. One type is characterized by the leaves with numerous veins. These remains were described as Podozamites irkutensis N. Nosova et Kiritch. (Nosova et al., 2017). The leaves of other types have a midvein. These leafy shoots are attributed to several taxa: Marskea sp. nov. (in press), Elatocladus falcatus (Heer) Prynada, E. heeriana N. Nosova et Kiritch., sp. nov., Elatocladus sp. and Pagiophyllum sp. Elatocladus falcatus (Heer) Prynada, 1962 (=Elatides falcata Heer, 1976) was described from the deposits of the lower subformation of the Prisayan Formation (the Aalenian) of the Ust’-Baley locality. An epidermal structure of the Elatocladus falcatus leaves is unknown. Here we designate the lectotype for E. falcatus. We have studied the leaf epidermal structure of the leafy shoots from the upper subformation of the Prisayan Formation (the Aalenian-Bajocian) in the localities Topka and Vladimirovka. Based on the morphological and epidermal features, we describe a new species Elatocladus heeriana. The shoots of E. heeriana have with helically arranged leaves. The leaves are sessile and dorsoventrally flattened, linear, lanceolate to falcate, with the tip curving toward the apex of the stem, with the broad and decurrent base and acute apex. The leaves are hypostomatic. They are characterized by straight to undulating anticlinal cell walls of the abaxial epidermis near the leaf edge and base. Stomata are arranged in two narrow bands, orientated transversely to irregularly. Subsidiary cells of the stomatal complexes are without papillae. Rare fragments of the Pagiophyllum sp. shoots were found in the deposits of the upper subformation of the Prisayan Formation (the Aalenian–Bajocian) in the localities Olkha and Vladimirovka. Their leaves are falcate, with a median keel on the abaxial side. The bad preservation of the cuticle did not allow us to study the epidermal pattern in details. Stomata are arranged in the bands, orientated irregularly. Subsidiary cells of the stomatal complexes are without papillae. One pollen cone (microstrobilus), attached presumably to the E. heeriana shoot, and several detached pollen cones of Schidolepium gracile Heer (1880) were found. The pollen cones are elongated, with numerous imbricate, helically arranged and dorsoventrally flattened microsporophylls. Sterile part of the microsporophyll expands to the distal lamina with acute apex. Some microsporophylls near the cone base are oval with rounded apex. The numerous microsporangia are visible in the apical part of the mature pollen cone, but a distal lamina of the microsporophylls often is indistinct here. Microsporangia (5–7 per microsporophyll) are elongated, fusiform. Pollen grains are spherical, nonsaccate, with the rugulate-perforate surface, apertures are invisible. The emended diagnosis is provided for the type species S. gracile, as well as the lectotype is designated.

Pollen cone production in jack pine: spatial and temporal patterns subject to natural disturbance by the jack pine budworm

Patterns of jack pine (Pinus banksiana Lambert) pollen cone production are of interest because they may help explain jack pine budworm (Choristoneura pinus pinus Freeman) outbreak patterns. We used generalized linear mixed models to analyze pollen cone production in 180 permanent plots in Ontario, Canada between 1992 and 2008. Pollen cone production increased with stand age, and large trees in sparsely-populated stands produced more pollen cones. Defoliation decreased the propensity of trees to produce pollen cones for at least two years. We also identified important patterns that are not explained by defoliation and stand characteristics. Pollen cone production is spatially synchronized among years, trees in central Ontario produced more pollen cones than trees in northwestern Ontario, and background cone production increased over time in the central region but not in more northwestern plots. Synchronized reproduction is common among tree species, but has not previously been noted for jack pine pollen cones. Increasing cone production in central Ontario may be evidence of changing forest and (or) climatic conditions and deserves further investigation. Our model can be used to quantitatively predict pollen cone production and assess the risk of jack pine budworm defoliation.