Seasonal Differences in Water-Use Sources of Impatiens hainanensis (Balsaminaceae), a Limestone-Endemic Plant Based on “Fissure-Soil” Habitat Function

Abstract

The southwestern mountains of Hainan Island are the southernmost region with tropical karst landform in China. The frequent alternation of dry and wet seasons leads to the loss of the mineral nutrients of limestone, creating karst fissure habitats. Plants living in karst fissure habitats for long periods of time have developed local adaptation mechanisms correspondingly. In the paper, hydrogen–oxygen stable isotope technology was applied to determine the water-use sources of Impatiens hainanensis in the dry and wet seasons, hoping to expound the adaptation mechanism of I. hainanensis in karst fissure habitats to the moisture dynamics in the wet and dry seasons. In the wet season (May to October, 2018), the air humidity is relatively high in the I. hainanensis habitat; in the dry season (November 2018 to April 2019), there is a degree of evaporation. In the wet season, fine-root biomass increases with soil depths, while coarse-root biomass decreases with soil depths; in the dry season, fine-root biomass is lower and coarse-root biomass is higher compared with the wet season. It was found that the average rainfall reached 1523 mm and the main water-use sources were shallow (0–5 cm) and middle (5–10 cm) soil water, epikarst water, and shallow karst fissure water during the wet season; the average rainfall reached 528 mm, and the deep (10–15 cm) soil water and shallow karst fissure water were the main water-use sources during the dry season. Fog water has a partial complementary effect in the dry season. The differences in the distribution of root biomass and each source of water in the wet and dry seasons of I. hainanensis also reflect the different water-use strategies of I. hainanensis in the wet and dry seasons. In both dry and wet seasons, I. hainanensis formed a water-use pattern dominated by soil water and shallow fissure water (0–15 cm) under the influence of the “fissure-soil-plant” system in the karst region.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology

“…However, in the F group, belowground biomass allocation decreased while aboveground (especially stem) biomass increased at both W100% and W30%. This nding aligns with previous studies (Markesteijn and Poorter 2009;Poorter et al 2012) and suggests that P. zhennan, as a tree species, tends to allocate more biomass to stems, enhancing water and nutrient transport e ciency between leaves and roots (Battie-Laclau et al 2016; Huang et al 2021), and providing additional support and protection to optimize light interception (Bloom et al 1985;Battie-Laclau et al 2016). However, under drought condition (W30%), P. zhennan seedlings shifted their biomass allocation strategy by reducing leaf biomass allocation and investing relatively more biomass resources in roots.…”

Biomass Allocation, Root Spatial Distribution, and the Physiological Response of Dalbergia odorifera Seedlings in Simulated Shallow Karst Fissure-Soil Conditions

“…There are many SKFs in KRD areas [5]. The water runoff will drive the surface soil to fill some SKFs, making them an important means of leakage and unique soil and water storage space [29]. The infertile and thin KRD soil, along with the insufficient water, nutrients, root growth, and plant development space from the surface soil, are the limiting factors for vegetation restoration [30][31][32].…”

Palynological and macroscopic characters evidence infer the evolutionary history and insight into pollination adaptation in Impatiens (Balsaminaceae)

“…As is well known, the characteristics of Impatiens fit the characteristics of the entomophilous flower, flowers are zygomorphic with secrete nectar by spur, the specialization of lower sepal for the easy landing of flower‐visiting insects, and complex reticulation can be found on the pollen surface (Tian, 2004; Cai et al, 2007; Gong & Huang, 2007; Xiao, 2009; Li, 2022). Impatiens show a higher diversity of flower color, it has many types of pollinating insects such as Sphingidae, bumble bees, and ants (Randall & Hilu, 1990; Mao et al, 2011; Zhong, 2014; Abrahamczyk et al, 2021). Since different pollinators are sensitive to various bands in the spectrum reflected by different flower colors, we speculate that the evolution of higher floral color diversity in Impatiens may be an adaptation to the increased preference for pollinators, and thus increases the probability of successful pollination.…”

“…The main pollinators of Impatiens capensis and Impatiens pallida in North America are bumblebees and honeybees (Rust, 1977; Randall & Hilu, 1990). Impatiens species of Madagascar are usually pollinated by flies (Abrahamczyk et al, 2021), and most of the Impatiens taxa growing in China are pollinated by bumblebees, bees, moths, and butterflies (Tian, 2004; Tian et al, 2004; Xiao, 2009; Tang & Huang, 2010; Mao et al, 2011; Zhong, 2014). In addition to the above species, the pollinators of Impatiens in Africa also include hummingbirds.…”