Water Metabolism of Lonicera japonica and Parthenocissus quinquefolia in Response to Heterogeneous Simulated Rock Outcrop Habitats

Abstract

The karst carbon sink caused by rock outcrops results in enrichment of the bicarbonate in soil, affecting the physiological process of plants in an all-round way. Water is the basis of plant growth and metabolic activities. In heterogeneous rock outcrop habitats, the impact of bicarbonate enrichment on the intracellular water metabolism of plant leaf is still unclear, which needs to be revealed. In this paper, the Lonicera japonica and Parthenocissus quinquefolia plants were selected as experimental materials, and electrophysiological indices were used to study their water holding, transfer and use efficiency under three simulated rock outcrop habitats, i.e., rock/soil ratio as 1, 1/4 and 0. By synchronously determining and analyzing the leaf water content, photosynthetic and chlorophyll fluorescence parameters, the response characteristics of water metabolism within leaf cells to the heterogeneous rock outcrop habitats were revealed. The results showed that the soil bicarbonate content in rock outcrop habitats increased with increasing rock/soil ratio. Under the treatment of a higher concentration of bicarbonate, the leaf intra- and intercellular water acquisition and transfer efficiency as well as the photosynthetic utilization capacity of P. quinquefolia decreased, the leaf water content was lower, and those plants had low bicarbonate utilization efficiency, which greatly weakened their drought resistance. However, the Lonicera japonica had a high bicarbonate use capacity when facing the enrichment of bicarbonate within cells, the above-mentioned capacity could significantly improve the water status of the leaves, and the water content and intracellular water-holding capacity of plant leaves in large rock outcrop habitats were significantly better than in non-rock outcrop habitats. In addition, the higher intracellular water-holding capacity was likely to maintain the stability of the intra- and intercellular water environment, thus ensuring the full development of its photosynthetic metabolic capacity, and the stable intracellular water-use efficiency also made itself more vigorous under karstic drought. Taken together, the results suggested that the water metabolic traits of Lonicera japonica made it more adaptable to karst environments.

Effects of Film-Mulched Rock Outcrops on Rainwater Redistribution and Maize Growth in the Cropland of a Rocky Karst Area

“…In addition, the rocks cover a great proportion of the surface area, and those rocks hinder soil layer continuity and reduce the use efficiency and productivity of the land [47][48][49]. Despite these factors, evidence still shows that the funneling effect of rock outcrops is expected to change the distribution pattern of rainwater and help alleviate the problem of crop water stress in karst farmland with scarce water resources [9,23,37]. Therefore, it is necessary to retain the rainwater intercepted by the rock outcrops to the maximum extent through film-mulched rock outcrops, as implemented in this study, which can effectively improve the soil water content of karst farmland and the utilization efficiency of precipitation by crops.…”

“…The infiltration process and redistribution of rainwater in rocky karst environments are strongly affected by rock outcrops [8,22,23]. The rocks extend from the surface to the underlying bedrock and will strongly induce the vertical infiltration of soil water and then inevitably reduce the soil's water-holding capacity due to their role in accelerating the conversion of surface water and groundwater [24][25][26].…”

“…To a certain degree, rock outcrops help improve soil moisture during rainfall when they collect and output rainwater for the surrounding soil, despite this effect varying markedly among karst ecosystems for some influencing factors, for example, the rock-soil interface, soil properties, and vegetation type [31][32][33]. In addition, rocks are an extensive landscape element of karst landforms, and changing the distribution of natural rainfall will inevitably affect plant growth [23,34,35]. In summary, rock outcrops can have positive and negative influences on the hydrology of karst areas.…”

Association of the electrical parameters and photosynthetic characteristics of the tea tree manifests its response to simulated karst drought

“… 13 Zhao et al found that a simulated karst drought reduced the intracellular water-holding capacity and water transfer rate of plants and improved the water utilization efficiency of Lonicera japonica and Parthenocissus quinquefolia . 24 More and more scholars are applying plant electrical parameters to the study of the water metabolism of plants. 23 , 25 However, it is still unclear how the intracellular and extracellular water in tea trees coordinate under water deficit, which remains to be revealed.…”