Morphological response of Vitex negundo var. heterophylla and Ziziphus jujuba var. spinosa to the combined impact of drought and shade

Abstract

Light and soil moisture availability are two important abiotic factors influencing plant growth in an agroforestry system. Different soil moisture and light treatments were applied to examine the combined impact of drought and shade on the morphological plasticity of Vitex negundo var. heterophylla (Chinese chastetree) and Ziziphus jujuba var. spinosa (Spine jujube). We found that the interaction of light and soil moisture was orthogonal in the two species. V. negundo captured irradiance efficiently with relatively long petiole and petiolule, while Z. jujuba maintained higher branches to absorb light than V. negundo. Compared to the seedlings under full sunlight, the palmately compound leaves of V. negundo under low light showed larger specific leaf area (SLA), lower ratio of leaflet length to width and higher leaf mass ratio (leaf biomass to total biomass); in contrast, the simple leaves of Z. jujuba under low light showed larger SLA and ratio of leaf length to petiole length. In both species, drought reduced the branch number, mean internode length of stem, and increased root mass ratio (root biomass to total biomass), but leaf morphology showed little variation to the decreased soil moisture. Between the two species, V. negundo is more shade-tolerant, while Z. jujuba is more droughttolerant. In an alley cropping system, the spacing can be smaller in the V. negundo-crop system than the Z. jujuba-crop system when soil moisture is adequate. However, the V. negundo-crop system should be managed with more caution under the soil moisture limited conditions.

Hierarchy of plasticity traits in responses of Quercus aliena to light conditions and water availability

“…Reduced SLA under high light suggested that the lower vapor-pressure deficit under shade compensated for high transpiration load from high SLA and drought (Quero et al 2006;Du et al 2013). Therefore, these results did not support predictions of the trade-off hypothesis that shade stress aggravated drought-induced damages (Smith and Huston 1989).…”

“…The watering regimes severed as severe, moderate, mild water deficit and well water conditions, respectively. The 10% sunlight was selected to simulate the irradiance of forest understory after measuring the irradiance of forest understory in local areas (Du et al 2013), and the 66% sunlight equaled to irradiance of forest gaps, which served as control here. Ten seedlings were used as replication in each water and light treatment combination.…”

“…Exploring mechanisms of plants' plastic responses to simultaneous light and water limitation is essential for understanding and explaining plants' capacity to adaptation in variable environments (Valladares et al 2006;Arend et al 2013), and improves the efficiency of the Grain to Green Projects in China. Water deficit is often the key factor adversely affecting reforestation practices of the Grain to Green Projects in arid and semi-arid areas (Du et al 2013). In addition, plants' adaptive response to heterogeneous forest light conditions is closely associated with successful restoration under limited soil water conditions.…”

Genetic and epigenetic variations associated with adaptation to heterogeneous habitat conditions in a deciduous shrub

“…The epigenetic mechanism may be restricted when natural plant populations endure some discrete human‐caused disturbance, such as heavy metal pollution (Kim et al., ), experimental disturbance (Herrera & Bazaga, ), and oil spills (Robertson et al., ). According to our field investigations and planting experiments (Du et al., ), Chinese chastetree tends to distribute in open habitats with plentiful light. Understory individuals might sometimes undergo aboveground dieback due to shade and drought, but individuals in open habitat were disturbed by human‐caused cutting in five (Fanggan, Liantaishan, Mengshan, Menglianggu, and Taishan) of seven study sites (see Figure a).…”

“…Chinese chastetree in roadside and bush habitats is frequently cut by farmers as firewood or to prevent it from occupying farmlands. It can adapt to cardinal environmental factors through modification of a series of morphological and physiological characteristics (Du, Guo, Zhang, & Wang, 2010;Du et al, 2012). As a long long-lived perennial, V. negundo var.…”