ORCID Profile
0000-0002-9365-6548
Current Organisations
Charles Sturt University
,
University of Tasmania
,
CSIRO Black Mountain Laboratories
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Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/BT17239
Abstract: Acacia s. str. (Mimosoideae, Fabaceae) is the largest plant genus in Australia (~1000 species). Its seeds have physical dormancy from a hard, water-impermeable testa. Heat from fire (natural systems) and hot water (nursery production) can break this dormancy. It is often reported that these treatments ‘soften’ or ‘crack’ the seed coat, but in practice they only affect a minute part of the seed coat, the lens. We examined lens structure in a wide range of Acacia species to determine what ersity of testa and lens structure was present, if there were differing responses to a hot water dormancy breaking treatment and if there were structural differences between soft- and hard-seeded species. Seed morphology, testa and lens structure were examined before and after hot water treatment (~90°C for one minute), in 51 species of Australian Acacia from all seven sections, from all states and territories of Australia and from a wide range of environments. Five of the species had been noted to produce non-dormant seed (‘soft-seeded’ species). Average seed mass per species ranged from 3.1 to 257.9 mg (overall average 24.2 mg, median 13.8 mg). Almost all species had a relatively thick seed coat (average 132.2 µm) with well-developed palisade cells (average 41.5 µm long) and a lens which ‘popped’ in response to hot water treatment. For 44 species ranging in average seed mass from 3.1 to 43.9 mg (×14 range), the unpopped lens area only ranged ×3 (11480–36040 µm2). The lens was small (in 88% of species the average length of the unpopped lens was µm) and the unpopped lens area was a minute proportion of seed surface area (average 0.10%). A. harpophylla (soft-seeded species) had a thin testa (37.3 µm) without obvious palisade cells and did not have a functional lens. In hard-seeded species the morphology of the popped lens varied widely, from a simple mound to complete detachment. A functional lens is not a universal feature in all genera of the Mimosoideae, including several species in a genus (Senegalia) previously included in Acacia s. lat. On the basis of the 51 investigated species a lens was present in all Australian acacias, although non-functional in two soft-seeded species. Although the lens was, on average, only ~1/1000th of the surface area of an Acacia seed and thus easily overlooked, it can have a profound influence on imbibition and germination. An assessment of lens structure, before and after heat treatment, can be of considerable use when interpreting the results of Acacia germination experiments.
Publisher: Wiley
Date: 30-07-2021
DOI: 10.1111/PPL.13500
Abstract: Differences in root morphology and acclimation to low‐phosphorus (P) soil were examined among eight legume species from the Trifolium Section Tricocephalum to understand how these root attributes determine P acquisition. Ornithopus sativus was included as a highly P‐efficient benchmark species. Plants were grown as microswards in pots with five rates of P supplied in a topsoil layer to mimic uneven P distribution within a field soil profile. Topsoil and subsoil roots were harvested separately to enable measurement of the nutrient‐foraging responses. Critical P requirement (lowest P supply for maximum yield) varied over a threefold range, reflecting differences in root morphology and acclimation of nutrient‐foraging roots to P stress. Among the species, there was a 3.2‐fold range in root length density, a 1.7‐fold range in specific root length, and a 2.1‐fold range in root hair length. O . sativus had the lowest critical P requirement, displayed a high root length density, the highest specific root length, and the longest root hairs. Acquisition of P from P‐deficient soil was facilitated by development of a large root hair cylinder (i.e. a large root–soil interface). This, in turn, was determined by the intrinsic root morphology attributes of each genotype, and the plasticity of its root morphology response to internal P stress. Root acclimation in low‐P soil by all species was mostly associated with preferential allocation of mass to nutrient‐foraging roots. Only O . sativus and four of the Trifolium species adjusted specific root length beneficially, and only O . sativus increased its root hair length in low‐P soil.
Publisher: Wiley
Date: 09-2022
DOI: 10.1002/PAN3.10378
Abstract: Competing land‐use demands for agriculture and nature conservation is one of the most significant global challenges. To improve the health of landscapes, collaborative transdisciplinary solutions are required. Environmental accounting is an attractive governance approach for helping to deliver healthy future landscapes however, the ersity of approaches to environmental accounting makes this field complex to navigate, which limits transdisciplinary collaboration and impedes implementation. We seek to address this issue by presenting a new framework to clarify environmental accounting. This framework classifies the currently disparate branches of the literature into four newly described environmental accounting types: Organisational Environmental Management Accounting, Organisational Environmental Reporting Accounting, Area Environmental Management Accounting and Area Environmental Reporting Accounting. The framework is then used to discuss, across multiple scales (organisational, ecosystem and national), existing environmental accounting tools which could assist in delivering healthy future landscapes, and areas for future research. Finally, we demonstrate the potential for environmental accounting research approaches (materiality assessment, dialogic accounting and critical accounting) to assist in defining healthy future landscapes. This paper presents the first substantial exploration of environmental accounting in the landscapes context and presents a research agenda to progress this exciting area of transdisciplinary research. Read the free Plain Language Summary for this article on the Journal blog.
Publisher: Cambridge University Press (CUP)
Date: 12-2019
DOI: 10.1017/S0960258519000242
Abstract: The seeds of most Australian acacias have pronounced physical dormancy (PY). While fire and hot water (HW) treatments cause the lens to ‘pop’ almost instantaneously, for many Acacia species the increase in germination percentage can be gradual. If PY is broken instantly by HW treatment, why is germination often an extended process? Control and HW treatments were performed on seeds of 48 species of Acacia . Seeds were placed on a moist substrate and imbibition was assessed by frequently weighing in idual seeds. In the two soft-seeded species all control seeds were fully imbibed within 6–24 h, while in hard-seeded species very few control seeds imbibed over several weeks. In 10 species over 50% of the HW-treated seeds imbibed within 30 h, but mostly the percentage of imbibed seeds gradually increased over several weeks. Some seeds in a replicate would imbibe early, while others would remain unimbibed for many days or weeks then, remarkably, become fully imbibed in less than 24 h. While HW treatment broke PY almost instantaneously, it appeared that in many Acacia species some other part of the testa slowed water from reaching the embryo. This process of having staggered imbibition may be a way of ensuring not all seeds in a population germinate after small rain events. Thus it appears the lens acts as a ‘fire gauge’ while some other part of the seed coat acts as a ‘rain gauge’.
No related grants have been discovered for Rowan Alden Hull.