Respon Genotipe Padi Lokal terhadap Cekaman Rendaman di Pembibitan

Uncertain climate change impacts the difficulty of predicting the intensity of floods that hit rice fields in flood-prone areas, both the duration of the submerged plants and the height of the water surface. In order to evaluate the tolerance level and response of several local rice genotypes to submersion stress in the vegetative phase, 50 rice genotypes were screened (47 North Sumatran local varieties, 3 VUB), using special ponds to simulate flooding or inundation stress. The study used a separate plot design with three replications; the main plot was three immersion models, namely full immersion, partial soaking, and not soaking, and subplots of 50 rice genotypes. The immersion treatment was defined as a different growing environment. The results showed that in the fully submerged treatment, the recovery capacity of local rice plants only ranged from 0-20%. The new, improved varieties tested were Inpari 4 (susceptible), Inpari 3, 10, Ciherang, Inpara 2 (very susceptible), Inpari 30, FR13A (very tolerant). Submersion tolerant genotypes had a slight increase in plant height after being fully submerged. The chlorophyll content in the leaves decreased immediately after the soaking stress period (14 DAP) in all rice genotypes. The local rice genotypes tested were very susceptible to immersion; the new superior variety Inpari 4 was categorized as susceptible, while Inpari 30 and FR13A were very tolerant.

Effects of Water Level Fluctuations on the Growth Characteristics and Community Succession of Submerged Macrophytes: A Case Study of Yilong Lake, China

Water level fluctuation (WLF) has a significant effect on aquatic macrophytes, but few experimental studies have examined the effect of WLF on submerged community succession, especially from a large-scale perspective. In this study, field monitoring of WLF and submerged macrophytes was conducted in Yilong Lake (SE China) over two years, and the impacts of WLF on the growth characteristics and the community structure of submerged macrophytes were determined. The results show that the biomass of submerged macrophytes decreased significantly after the water level increased and submerged macrophytes could cope with the adverse environment by adjusting their growth posture, for example, increasing plant length and reducing branch number. However, different submerged plants have different regulatory abilities, which leads to a change in the community structure. Myriophyllum spicatum, Stuckenia pectinata, and Najas marina had better adaptation abilities to WLF than Najas minor and Utricularia vulgaris. Changes in water depth, dissolved oxygen, and transparency significantly contribute to the effect of WLF on submerged plant communities. Therefore, when determining the range of WLF, the above three critical factors and submerged plant species should be considered. WLF changed the spatial distribution of the aquatic plant community. When water levels rose, the density of the submerged macrophyte community in the original growth region reduced as the emergent plants migrated to shallower water, and the seed bank germination was aided by transparent water produced among emergent plants. This can be used as a pioneering measure to restore submerged plants in eutrophic lakes with low transparency. In addition, a suitable water depth created by WLF was conducive to activating the seed bank and improving the diversity of aquatic plants. Finally, a distribution map of aquatic plants in Yilong Lake is drawn.

Responses of morphological and physiological traits to herbivory by snails of three invasive and native submerged plants

Aims The submerged plant species Carolina fanwort (Cabomba caroliniana) has become a dominant invasive aquatic plant in the Lake Taihu Basin (LTB) in China. Introduced species may escape their original specialist enemies and encounter fewer enemies in their new environment. They were assumed to have suffered less herbivory than native species as they are relatively unpalatable (the enemy release hypothesis (ERH)). The objective of this study was to compare the responses of C. caroliniana with those of co-occurring native species to herbivory from native herbivores. Methods We conducted a mesocosm experiment to record the responses of C. caroliniana and two commonly co-occurring native submerged plant counterparts, water thyme (Hydrilla verticillata) and Eurasian watermilfoil (Myriophyllum spicatum), to herbivory by two native generalist gastropod snails, Radix swinhoei and Sinotaia quadrata. Plant morphological traits (total biomass, shoot/root (S/R) biomass ratio and relative growth rate (RGR)) and physiological traits (leaf total nonstructural carbohydrate (TNC), lignin, and cellulose) were recorded. Important Findings The snail S. quadrata rarely influenced the plant traits of the three submerged plants. With the increasing numbers of R. swinhoei treatments, most of the plant traits of H. verticillata and M. spicatum changed, while those of C. caroliniana showed a relatively stable fluctuation. This result indicates that C. caroliniana is more resistant to herbivory by the snail R. swinhoei, which is consistent with the ERH hypothesis. This finding indicates that herbivorous snail species contributes to the invasion of C. caroliniana, which potentially alters the species composition of submerged plants in the plant community.

Metagenomic insights into the effects of submerged plants on functional potential of microbial communities in wetland sediments

Submerged plants in wetlands play important roles as ecosystem engineers to improve self-purification and promote elemental cycling. However, their effects on the functional capacity of microbial communities in wetland sediments remain poorly understood. Here, we provide detailed metagenomic insights into the biogeochemical potential of microbial communities in wetland sediments with and without submerged plants (i.e., Vallisneria natans). A large number of functional genes involved in carbon (C), nitrogen (N) and sulfur (S) cycling were detected in the wetland sediments. However, most functional genes showed higher abundance in sediments with submerged plants than in those without plants. Based on the comparison of annotated functional genes in the N and S cycling databases (i.e., NCycDB and SCycDB), we found that genes involved in nitrogen fixation (e.g., nifD/H/K/W), assimilatory nitrate reduction (e.g., nasA and nirA), denitrification (e.g., nirK/S and nosZ), assimilatory sulfate reduction (e.g., cysD/H/J/N/Q and sir), and sulfur oxidation (e.g., glpE, soeA, sqr and sseA) were significantly higher (corrected p < 0.05) in vegetated vs. unvegetated sediments. This could be mainly driven by environmental factors including total phosphorus, total nitrogen, and C:N ratio. The binning of metagenomes further revealed that some archaeal taxa could have the potential of methane metabolism including hydrogenotrophic, acetoclastic, and methylotrophic methanogenesis, which are crucial to the wetland methane budget and carbon cycling. This study opens a new avenue for linking submerged plants with microbial functions, and has further implications for understanding global carbon, nitrogen and sulfur cycling in wetland ecosystems.

Generality and Shifts in Leaf Trait Relationships Between Alpine Aquatic and Terrestrial Herbaceous Plants on the Tibetan Plateau

Plant traits mirror both evolutionary and environmental filtering process with universal trait-trait relationships across plant groups. However, plants also develop unique traits precisely to different habitats, inducing deviations of the trait coupling relations. In this study, we aimed to compare the differences in leaf traits and examine the generality and shifts of trait-trait relationships between alpine aquatic and terrestrial herbaceous plants on the Tibetan Plateau, to explore the precise adaptive strategies of aquatic and terrestrial plants for its habitats. We measured mass-based and area-based leaf N and P concentrations, N:P ratios and specific leaf area (SLA) of aquatic and terrestrial herbaceous plants. Standardized major axis analysis were applied to build the correlations for every trait pairs of each plant group, and then to compare the differences in the trait-trait correlations among different plant groups. Leaf Nmass and Pmass of two groups of aquatic plants (emergent and submerged plants) were higher, but N:P ratios were lower than those of two groups of terrestrial plants (sedges and grasses). Submerged plants had extremely high SLA, while grasses had the lowest SLA. Nmass positively correlated with Pmass in three out of four plant groups. The two terrestrial plant groups had positive Nmass-SLA relationships but these two traits coupled weakly in aquatic plants. Pmass showed positive relationships to SLA in three out of four plant groups. Significant shifts of trait-trait relationships between aquatic and terrestrial plants were observed. In general, aquatic plants, especially submerged plants, are characterized by higher SLA, greater leaf nutrientmass than terrestrial plants, tend to pursue fast-return investment strategies, and represent the acquisitive end of leaf economics spectrum. The deviations of trait-trait relationships between different plant groups reveal the precise adaptions of submerged plants to the unique aquatic habitats.