Overexpression of PdeGATA3 results in a dwarf phenotype in poplar by promoting the expression of PdeSTM and altering the content of gibberellins.

In previous studies, GA20 oxidase (GA20ox) has been identified to be an important enzyme in the biosynthesis of GA, and SHOOTMERISTEMLESS (STM) can repress the expression of GA20ox. In this study, the GATA transcription factor PdeGATA3 was identified in the poplar line NL895, and its overexpression (OE) transgenic lines showed a dwarf phenotype. RNA sequencing (RNA-Seq) analysis suggested that OE PdeGATA3 could promote the expression of PdeSTM and repress the expression of PdeGA20ox. Therefore, we hypothesized that PdeGATA3 would directly promote the expression of PdeSTM and that PdeSTM would repress the expression of PdeGA20ox. Four experiments, a dual-luciferase reporter assay, GUS transient coexpression assay, yeast one-hybrid assay and electrophoretic mobility shift assay, were conducted and verified that PdeGATA3 could promote the expression of PdeSTM by binding GATA-Boxes in its promoter. OE PdeSTM in poplar resulted in a dwarf phenotype and repressed the expression of PdeGA20ox. GA measurement of the OE PdeSTM and PdeGATA3 lines showed that GA3 and GA4 contents were significantly lower than those in the wild type (WT). Accordingly, we put forward a regulation model involving plant height regulation by PdeGATA3, PdeSTM and PdeGA20ox.

Overexpression of PdeGATA3 results in a dwarf phenotype.

In previous studies, GA20 oxidase (GA20ox) has been identified to be an important enzyme in the biosynthesis of GA, and SHOOTMERISTEMLESS (STM) can repress the expression of GA20ox. In this study, the GATA transcription factor (TF) PdeGATA3 was identified in the poplar line NL895, and its overexpression (OE) transgenic lines showed a dwarf phenotype. RNA sequencing (RNA-Seq) analysis suggested that OE PdeGATA3 could promote the expression of PdeSTM and repress the expression of PdeGA20ox. Therefore, we hypothesized that PdeGATA3 would directly promote the expression of PdeSTM and that PdeSTM would repress the expression of PdeGA20ox. Four experiments, a dual-luciferase reporter assay, GUS transient coexpression assay, yeast one-hybrid (Y1H) assay, and electrophoretic mobility shift assay (EMSA), were conducted and verified that PdeGATA3 could promote the expression of PdeSTM by binding GATA-Boxes in its promoter. OE PdeSTM in poplar resulted in a dwarf phenotype and repressed the expression of PdeGA20ox. GA measurement of the OE PdeSTM and PdeGATA3 lines showed that GA3 and GA4 contents were significantly lower than those in the wild type (WT). Accordingly, we put forward a regulation model involving plant height regulation by PdeGATA3, PdeSTM and PdeGA20ox.

The Landscape of Autophagy-Related (ATG) Genes and Functional Characterization of TaVAMP727 to Autophagy in Wheat.

Autophagy is an indispensable biological process and plays crucial roles in plant growth and plant responses to both biotic and abiotic stresses. This study systematically identified autophagy-related proteins (ATGs) in wheat and its diploid and tetraploid progenitors and investigated their genomic organization, structure characteristics, expression patterns, genetic variation, and regulation network. We identified a total of 77, 51, 29, and 30 ATGs in wheat, wild emmer, T. urartu and A. tauschii, respectively, and grouped them into 19 subfamilies. We found that these autophagy-related genes (ATGs) suffered various degrees of selection during the wheat's domestication and breeding processes. The genetic variations in the promoter region of Ta2A_ATG8a were associated with differences in seed size, which might be artificially selected for during the domestication process of tetraploid wheat. Overexpression of TaVAMP727 improved the cold, drought, and salt stresses resistance of the transgenic Arabidopsis and wheat. It also promoted wheat heading by regulating the expression of most ATGs. Our findings demonstrate how ATGs regulate wheat plant development and improve abiotic stress resistance. The results presented here provide the basis for wheat breeding programs for selecting varieties of higher yield which are capable of growing in colder, drier, and saltier areas.

Impacts of stand density on diversity of understory plant and soil seed banks in a Pinus massoniana plantation.

Stand density is a critical factor impacting the diversity of understory plants. We analyzed the diversity of understory plants and soil seed banks, as well as their relationship by setting up three planting densities in a Pinus massoniana plantation, including low density (1575 trees·hm-2, D1), medium (2474 trees·hm-2, D2), and high (3550 trees·hm-2, D3). It aimed to provide a scientific basis for the implementation of the multi-objective sustainable development of plantations. The results showed that there were 70 species of herbs and shrubs belonging to 42 families and 62 genera. D1 was dominated by heliophiles, whereas both the D2 and D3 were dominated by shade-tolerant species. The Margalef (M), Shannon (H), Simpson (D), Pielou (Jsw), and Altalo (Al) indices of the herbs and shrubs exhibited a downward trend with increasing stand den-sity. In the herb layer, D1 and D3 showed significant difference in H, D, Jsw and Al. There were significant differences of Jsw and Al in the shrub layer among the three stand densities, but no diffe-rence of H and D. H, D, Jsw and Al in the soil seed bank first decreased and then increased with increasing stand density, with species richness and diversity being the highest in D1. The similarity coefficient of Jaccard and Sorensen among different stand densities was low. In the herb layer, M was positively correlated with Jsw. The correlations between stand density and H, D, Jsw and Al were greater in the shrub layer than in the herb layer. There was significant negative correlation between stand density and Jsw both in the shrub and herb layers. The stand density of 1575 trees·hm-2 was comparatively beneficial for the development of understory, plant diversity, and sustainability of P. massoniana plantation.

Genomic and Phenotypic Divergence in Wild Barley Driven by Microgeographic Adaptation.

Microgeographic adaptation is a fundamental driving force of evolution, but the underlying causes remain undetermined. Here, the phenotypic, genomic and transcriptomic variations of two wild barley populations collected from sharply divergent and adjacent micro-geographic sites to identify candidate genes associated with edaphic local adaptation are investigated. Common garden and reciprocal transplant studies show that large phenotypic differentiation and local adaptation to soils occur between these populations. Genetic, phylogenetic and admixture analyses based on population resequencing show that significant genetic divergences occur between basalt and chalk populations. These divergences are consistent with the phenotypic variations observed in the field. Genome sweep analyses reveal 162.7 Mb of selected regions driven by edaphic local adaptation, in which 445 genes identified, including genes associated with root architecture, metal transport/detoxification, and ABA signaling. When the phenotypic, genomic and transcriptomic data are combined, HvMOR, encoding an LBD transcription factor, is determined to be the vital candidate for regulating the root architecture to adapt to edaphic conditions at the microgeographic scale. This study provides new insights into the genetic basis of edaphic adaptation and demonstrates that edaphic factors may contribute to the evolution and speciation of barley.

Repellency of forty-one aromatic plant species to the Asian citrus psyllid, vector of the bacterium associated with huanglongbing.

Huanglongbing (HLB) is the most devastating citrus disease worldwide. The organism associated with the disease is spread by an insect vector, Diaphorina citri, commonly known as Asian citrus psyllid (ACP). Current management of HLB relies either on physical removal of the infected plants or on chemical control of ACP. Both methods are costly and not overly effective. In addition, public concerns regarding insecticide residues in fruit have greatly increased in recent years. It has been hypothesized that plant volatiles could act as repellents to ACP, thus reduce the incidence of HLB. To test this hypothesis, the repellency of fresh tissues of 41 aromatic plant species to ACP was investigated. The repellency of individual species was determined using a Y-tube olfactometer. Our results showed that volatiles of five plant species were highly effective in repelling ACP with repellency as much as 76%. Among these, the tree species, Camptotheca acuminate, and the two shrubs, Lantana camara and Mimosa bimucronata, could potentially be planted as a landscape barrier. The two herbs, Capsicum annuum and Gynura bicolor, could potentially be used as interplantings in orchards. This is the first time that the repellency of fresh tissues from a diverse range of plant species to ACP has been determined. Although further field evaluation of various interplanting regimes and landscape barriers are needed to assess their effectiveness, our results showed that these aromatic species, being highly repellent to ACP, offer great potential as more cost-effective and environmentally sustainable alternatives to the current methods of managing HLB.

Coexpression analysis of a large-scale transcriptome identified a calmodulin-like protein regulating the development of adventitious roots in poplar.

Poplars are important woody plants, and the ability to form adventitious roots (ARs) is the key factor for their cultivation because most poplars are propagated by cloning. In previous studies, Ca2+ was confirmed to regulate AR formation in poplar. In this study, wild-type poplar cuttings grown in 1.0 mM Ca2+ solution showed the best visible performance of AR development. Coexpression analysis of a large-scale RNA-Seq transcriptome was conducted to identify Ca2+-related genes that regulate AR development in poplar. A total of 15 coexpression modules (CMs) were identified, and two CMs showed high association with AR development. Functional analysis identified a number of biological pathways, including 'oxidation-reduction process', 'response to biotic stimulus' and 'metabolic process', in tissues of AR development. The Ca2+-related pathway was specifically selected, and its regulation in poplar AR development was predicted. A Ca2+ sensor, PdeCML23-1, which is a member of the calmodulin-like protein (CML) family, was found to promote AR development by phenotypic assay of overexpressed PdeCML23-1 transgenic lines at various growing conditions. By measuring cytosolic Ca2+ in AR tips, PdeCML23-1 seemed to play a role in decreasing cytosolic Ca2+ concentration. Additionally, the expression profiles of some genes and phytohormone indole acetic acid (IAA) were also changed in the overexpressed PdeCML23-1 transgenic lines. According to this study, we were able to provide a global view of gene regulation for poplar AR development. Moreover, we also observed the regulation of cytosolic Ca2+ concentration by PdeCML23-1, and this regulation was involved in AR development in poplar. We also predicted that PdeCML23-1 possibly regulates AR development by modulating IAA content in poplar.

The impacts of climate changes and human activities on net primary productivity vary across an ecotone zone in Northwest China.

The variations in net primary productivity (NPP) and its controls are critical to understand the mechanisms that maintain ecosystem services under ongoing climate change and human activities. However, such knowledge is still incomplete in ecotone areas where plant species may reach their physiological thresholds. Our study quantified the variations in NPP and its controls resulting from interannual climate variations and human activities in the Qilian Mountain region (QLMR), an ecotone zone in central Asia. To achieve this goal, three indexes, including actual NPP (ANPP), potential NPP (PNPP), and human-induced NPP (HNPP), and their variations during 2001-2012 were estimated by combining the Carnegie-Ames-Stanford approach and a residual trend method. The results showed that the average PNPP, HNPP and ANPP values across the whole QLMR increased at rates of 4.71, 3.08, and 1.63 g C m-2 yr-1, respectively. The ANPP increased in 66.8% of the area during 2001-2012. The impacts of climate variations and human activities on NPP varied across the ecotone zone, vegetation types and altitudinal gradient. Climate-derived impacts caused the ANPP to increase in over 53% of the area in all vegetation ecosystems except forests. Climate variations were expected to account for most of the changes in ANPP in high-altitude zones (above 3500 m), while the impacts of human activities on ANPP were concentrated mainly in mid- and low-elevation zones. Our results suggest that increasing precipitation is a dominant factor underlying the increase in ANPP in such semiarid regions, while human activity is the primary reason for declines in NPP even if there is vegetation restoration. To improve the functions of vegetation ecosystems in such ecotones, a holistic strategy that combines spatially distinct measures is urgently needed.

The improved assembly of 7DL chromosome provides insight into the structure and evolution of bread wheat.

Wheat is one of the most important staple crops worldwide and also an excellent model species for crop evolution and polyploidization studies. The breakthrough of sequencing the bread wheat genome and progenitor genomes lays the foundation to decipher the complexity of wheat origin and evolutionary process as well as the genetic consequences of polyploidization. In this study, we sequenced 3286 BACs from chromosome 7DL of bread wheat cv. Chinese Spring and integrated the unmapped contigs from IWGSC v1 and available PacBio sequences to close gaps present in the 7DL assembly. In total, 8043 out of 12 825 gaps, representing 3 491 264 bp, were closed. We then used the improved assembly of 7DL to perform comparative genomic analysis of bread wheat (Ta7DL) and its D donor, Aegilops tauschii (At7DL), to identify domestication signatures. Results showed a strong syntenic relationship between Ta7DL and At7DL, although some small rearrangements were detected at the distal regions. A total of 53 genes appear to be lost genes during wheat polyploidization, with 23% (12 genes) as RGA (disease resistance gene analogue). Furthermore, 86 positively selected genes (PSGs) were identified, considered to be domestication-related candidates. Finally, overlapping of QTLs obtained from GWAS analysis and PSGs indicated that TraesCS7D02G321000 may be one of the domestication genes involved in grain morphology. This study provides comparative information on the sequence, structure and organization between bread wheat and Ae. tauschii from the perspective of the 7DL chromosome, which contribute to better understanding of the evolution of wheat, and supports wheat crop improvement.

N6-methyladenosine regulatory machinery in plants: composition, function and evolution.

N6-methyladenosine (m6A) RNA methylation, one of the most pivotal internal modifications of RNA, is a conserved post-transcriptional mechanism to enrich and regulate genetic information in eukaryotes. The scope and function of this modification in plants has been an intense focus of study, especially in model plant systems. The characterization of plant m6A writers, erasers and readers, as well as the elucidation of their functions, is currently one of the most fascinating hotspots in plant biology research. The functional analysis of m6A in plants will be booming in the foreseeable future, which could contribute to crop genetic improvement through epitranscriptome manipulation. In this review, we systematically analysed and summarized recent advances in the understanding of the structure and composition of plant m6A regulatory machinery, and the biological functions of m6A in plant growth, development and stress response. Finally, our analysis showed that the evolutionary relationships between m6A modification components were highly conserved across the plant kingdom.

Transcriptome and Proteome-Based Network Analysis Reveals a Model of Gene Activation in Wheat Resistance to Stripe Rust.

Stripe rust, caused by the pathogen Puccinia striiformis f. sp. tritici (Pst), is an important fungal foliar disease of wheat (Triticum aestivum). To study the mechanism underlying the defense of wheat to Pst, we used the next-generation sequencing and isobaric tags for relative and absolute quantification (iTRAQ) technologies to generate transcriptomic and proteomic profiles of seedling leaves at different stages under conditions of pathogen stress. By conducting comparative proteomic analysis using iTRAQ, we identified 2050, 2190, and 2258 differentially accumulated protein species at 24, 48, and 72 h post-inoculation (hpi). Using pairwise comparisons and weighted gene co-expression network analysis (WGCNA) of the transcriptome, we identified a stress stage-specific module enriching in transcription regulator genes. The homologs of several regulators, including splicing and transcription factors, were similarly identified as hub genes operating in the Pst-induced response network. Moreover, the Hsp70 protein were predicted as a key point in protein⁻protein interaction (PPI) networks from STRING database. Taking the genetics resistance gene locus into consideration, we identified 32 induced proteins in chromosome 1BS as potential candidates involved in Pst resistance. This study indicated that the transcriptional regulation model plays an important role in activating resistance-related genes in wheat responding to Pst stress.

Transcriptional Dynamics of Grain Development in Barley (Hordeum vulgare L.).

Grain development, as a vital process in the crop's life cycle, is crucial for determining crop quality and yield. However, the molecular basis and regulatory network of barley grain development is not well understood at present. Here, we investigated the transcriptional dynamics of barley grain development through RNA sequencing at four developmental phases, including early prestorage phase (3 days post anthesis (DPA)), late prestorage or transition phase (8 DPA), early storage phase (13 DPA), and levels off stages (18 DPA). Transcriptome profiling found that pronounced shifts occurred in the abundance of transcripts involved in both primary and secondary metabolism during grain development. The transcripts' activity was decreased during maturation while the largest divergence was observed between the transitions from prestorage phase to storage phase, which coincided with the physiological changes. Furthermore, the transcription factors, hormone signal transduction-related as well as sugar-metabolism-related genes, were found to play a crucial role in barley grain development. Finally, 4771 RNA editing events were identified in these four development stages, and most of the RNA editing genes were preferentially expressed at the prestore stage rather than in the store stage, which was significantly enriched in "essential" genes and plant hormone signal transduction pathway. These results suggested that RNA editing might act as a 'regulator' to control grain development. This study systematically dissected the gene expression atlas of barley grain development through transcriptome analysis, which not only provided the potential targets for further functional studies, but also provided insights into the dynamics of gene regulation underlying grain development in barley and beyond.

Evolutionary history of fire-stimulated resprouting, flowering, seed release and germination.

Fire has shaped the evolution of many plant traits in fire-prone environments: fire-resistant tissues with heat-insulated meristems, post-fire resprouting or fire-killed but regenerating from stored seeds, fire-stimulated flowering, release of on-plant-stored seeds, and germination of soil-stored seeds. Flowering, seed release and germination fit into three categories of response to intensifying fire: fire not required, weakly fire-adapted or strongly fire-adapted. Resprouting also has three categories but survival is always reduced by increasing fire intensity. We collated 286 records for 20 angiosperm and two gymnosperm families and 50 trait assignments to dated phylogenies. We placed these into three fire-adapted trait types: those associated with the origin of their clade and the onset of fire-proneness [primary diversification, contributing 20% of speciation events over the last 120 million years (My)], those originating much later coincident with a change in the fire regime (secondary diversification, 30%), and those conserved in the daughter lineage as already adapted to the fire regime (stabilisation, 50%). All four fire-response types could be traced to >100 My ago (Mya) with pyrogenic flowering slightly younger because of its dependence on resprouting. There was no evidence that resprouting was always an older trait than either seed storage or non-sprouting throughout this period, with either/both ancestral or derived in different clades and times. Fire-adapted traits evolved slowly in the Cretaceous, 120-65 Mya, and rapidly but fitfully in the Cenozoic, 65-0 Mya, peaking over the last 20 My. The four trait-types climaxed at different times, with the peak in resprouter speciation over the last 5 My attributable to fluctuating growing conditions and increasing savanna grasslands unsuitable for non-sprouters. All experienced a trough in the 40-30-Mya period following a reduction in world temperatures and oxygen levels and expected reduced fire activity. Thick bark and serotiny arose in the Mid-Cretaceous among extant Pinaceae. Heat-stimulated germination of hard seeds is ancestral in the 103-My-old Fabales. Smoke-(karrikin)-stimulated germination of non-hard seeds is even older, and includes the 101-My-old Restionaceae-Anarthriaceae. A smoke/karrikin response is detectable in some fire-free lineages that prove to have a fire-prone ancestry. Among clades that are predominantly fire-prone, absence of fire-related traits is the advanced condition, associated either with increased fire frequency (loss of serotiny and soil storage), or migration to fire-free habitats (loss of thick bark, pyrogenic flowering, serotiny or soil storage). Protea (Africa) and Hakea (Australia) illustrate the importance of stabilisation processes between resprouting/non-sprouting in accounting for speciation events over the last 20 My and highlight the frequent interchange possible between these two traits. Apart from Pinus, most ancestral trait reconstruction relative to fire has been conducted on predominantly Southern Hemisphere clades and this needs to be redressed. Despite these limitations, it is clear that fire has had a profound effect on fire-related trait evolution worldwide, and set the platform for subsequent evolution of many non-fire-related traits. Genetics of the triggering mechanisms remain poorly understood, except the karrikin system for smoke-stimulated germination. We exhort biologists to include fire-proneness and fire-related traits in their thinking on possible factors controlling the evolution of plants.

Impervious surface area is a key predictor for urban plant diversity in a city undergone rapid urbanization.

Urban biodiversity has increasingly been recognized by the scientific community and environmental policymakers as a part of conservation efforts worldwide. However, most studies on urban biodiversity focus on cities in developed countries. An information gap exists for urban biodiversity of cities in developing countries. Here we focused on variability in plant diversity, a major component of biodiversity, in a Chinese city that has undergone rapid urbanization in recent time. The influence of urbanization was determined by comparing plant diversity and proportion of exotic/endemic plant species with the intensity of urbanization across the study area. We used percentage of total impervious surface area (PTIA) as an indicator of urbanization intensity, ranging from 5% to 95% across the study area. In the study area, a total of 321 plant species was recorded, totaling 83 trees, 113 shrubs and 125 herbs. Plant diversity, measured by number of plant taxa and other indices, was driven by PTIA; an increase in PTIA reduced plant diversity. In addition, the ratio of exotic to endemic plant species increased as PTIA increased. Among the exotic species, most of the tree and shrub species were purposely introduced. Above 40% PTIA, plant diversity decreased sharply and the proportion of exotic species rose. As a valuable predictor of urban biodiversity, PTIA can thus be used as a key criterion for urban planning to ameliorate urban biodiversity. Further, our findings extend current understanding of urban biodiversity for cities in developing countries.

Improving conservation effectiveness of nature reserve for golden snub-nosed monkey, a niche-based approach.

Reserve selections are often opportunistic rather than strategic and coordinated, and consequently, many reserves are ineffective to achieve their intended goals of conservation. Here, we assessed the conservation effectiveness of a reserve for the golden snub-nosed monkeys (Rhinopithecus roxellana) with a niche-based approach. We assessed habitat usage of the monkeys in Shennongjia Nature Reserve (SNR) and attributes of 14 environmental variables that could potentially affect the monkeys' habitat use. Spatial distribution of potentially suitable habitat for the monkeys was then modeled with Maxent, a niche-based model, and conservation effectiveness of SNR was assessed by comparing the current boundary of the reserve with the spatial distribution of the modeled potential habitat and the current habitat area of the monkeys. Only 59% of the habitat area and 61% of the predicted potential habitat area were under the protection of SNR. To improve conservation effectiveness of SNR, we proposed that the current SNR be enlarged by 270 km2. The enlarged reserve would encompass 100% of the existing habitat area plus 89% of the predicted potential habitat area. Using the niche-based approach, we were able to integrate habitat usage data of the target species with that of remote sensing to identify areas potentially suitable as habitat for the species. This information can be used not only for improving conservation effectiveness of existing reserves but also for the effective planning and designing of new reserves.

Effects of mixed leaf litter from predominant afforestation tree species on decomposition rates in the Three Gorges Reservoir, China.

To determine whether mixed plantations can improve nutrient cycling and to elucidate the mechanisms of such effects, a field litterbag experiment with seven treatments involving Pinus massoniana (P.), Cupressus funebris (C.) and Quercus variabilis (Q.) litter in equal mass proportions (pure litter; pairwise combinations; and the combination of all three species) was conducted in a Pinus massoniana plantation in the region of the Three Gorges Reservoir, China. We measured mass loss and the release of C, N and P from the litter treatments and assessed the effects of mixing litter in each sampling phase and for various decomposition periods. At the end of the study, the mass loss and release of C, N and P among the treatments relative to their initial contents ranged from 47.6% to 62.8%, 59.5% to 75.2%, 63.5% to 78.2% and 58.9% to 72.6%, respectively. Primary mass loss and nutrient release occurred during a phase with high temperatures and precipitation, and decomposition was closely correlated with the initial lignin/N ratio and N concentration. Compared with the decay values of Quercus litter, mixing litter increased N release by 1.2% for the P. + Q. and C. + Q. combinations and increased P release by 3.0-6.3% for the three litter mixture combinations. Additionally, the P. + Q. and C. + Q. two-species mixtures exhibited greater decay than the three-species mixture. Mixing the two coniferous species (P. + C.) also increased decomposition. Furthermore, positive nonadditive mass loss occurred after incubation for 240 d, and mixing effects on the nonadditive release of C, N and P occurred immediately in 60 d incubations in all treatments. In conclusion, mixing these three species or two of species can improve material cycling in plantations, and Quercus appears to be a priority candidate for mixed planting with Pinus and/or Cupressus.

Spatial variability of soil organic carbon in Three Gorges Reservoir area, China.

Soil organic carbon (SOC) is an important component of the global carbon pool. It is a critical indicator of soil quality. We studied SOC content (SOCC) and SOC density (SOCD) of the Three Gorges Reservoir (TGR) area in China. Soil samples from 306 sites across the study area were assessed for SOCC, SOCD and bulk density. Total SOC stocks in the TGR area were estimated at 5.82×10-1Pg. We examined relationships between SOCC and SOCD, and the environmental and land-use/land-cover (LULC) variables. The plow layer (0-0.3m) had a significantly higher mean SOCC (20.6gkg-1) than the subsoil layer (16.5gkg-1); elevation, LULC, soil type and soil thickness were the most influential factors affecting SOCC in the plow layer. In the subsoil layer, elevation and soil thickness were dominant in determining SOCC and SOCD. To study the spatial variability of SOC, we used statistical modeling and GIS-based techniques to map the distribution of SOCC and SOCD of the study area. Both SOCC and SOCD in the plow layer showed patchy distribution and were positively correlated with elevation and vegetation coverage. Spatial variability of SOCD in the subsoil layer showed a gradual transition between LULC categories. The lower SOCC of farmland appeared to be related to the repeated removal of agricultural produce from the land. Preservation of permanent vegetation cover and changing of the traditional farming practices will help to improve SOC stock and increase soil productivity in the TGR area.

Differential passage time of mistletoe fruits through the gut of honeyeaters and flowerpeckers: effects on seedling establishment.

McKey's (1975) hypothesis that avian dispersers with a specialized gut provide higher quality seed dispersal than unspecialized frugivores was tested using grey mistletoe (Amyema quandang) fruits, and captive mistletoebirds (Dicaeum hirundinaceum) and spinycheeked honeyeaters (Acanthagenys refogularis) in arid South Australia. Mistletoebirds have a specialized gut, unlike spiny-cheeked honeyeaters. The gut passage time of A. quandang fruits through mistletoebirds was 820±29 s (mean±SE, n=188), compared to 2434±36 s (n=436) for honeyeaters. The seeds defecated by both bird species were deployed on twigs of host trees. Despite the longer retention time of fruit in the gut of honeyeaters, the germination percentage of seeds defecated by mistletoebirds (85% of 485 seeds) and honeyeaters (81% of 485 seeds) did not differ significantly 1 week after deployment. However, after 5 months, a significantly greater proportion of seedlings had established from seeds passed by mistletoebirds (42.7%) than from seeds defecated by honeyeaters (31.1%). The data support the notion that the more gentle treatment of seeds in the gut of specialized dispersers translates into higher seedling establishment.