| The area of karst regions in China is nearly1/3of the whole China, which concentrates in the southwestern mountains with a high population density. Due to the limitation of geographical conditions, agriculture is an important pillar industry in these karst areas. Among agriculture, maize (Zea mays L.) production is of great importance. Therefore, maize is one of the most significant ways for agricultural development. Drought and high calcium are the main features of the soils in the karst areas, which have serious impacts on the survival and reproduction of plants. Along with the contradiction between people and land, as well as the intensified soil erosion, the farmed production in karst areas might be threatened directly. Some researchers found that arbuscular mycorrhizal fungi (AMF) is one kind of soil microbes that is widely associated with plants. The AMF has been shown to enhance the survival of plants under stresses. Up to now, the attention of AMF in the karst areas has been paid to the ecological effects of AMF under single drought stress. However, the soils in karst areas are heterogeneous, and limiting factors for the growth of plants in different karst soils is various as well. Thus, it is necessary to consider the effects of AMF on plant under the stress of single drought, high calcium and their combination in the karst areas. This will be significant to the further understanding of mycorrhizal ecology and the sustainable development of agriculture in karst regions. Therefore, maize seedlings were selected as test materials in this research. In order to explore the effects of AMF on the growth, morphology, photosynthesis, nutrient and metabolism of maize seedlings in different karst soil conditions, three treatments including drought, high concentration of calcium (high Ca), and their combination (double stress) were applied to potted maize seedlings.1Effects of AMF on the morphological plasticity and biomass allocation pattern of maize seedlingsIn order to explore the effects of AMF on the morphological plasticity and biomass allocation pattern of maize (Zea mays L.) under various stresses, three treatments including drought, high concentration of calcium (high Ca). and their combination (double stress) were applied to potted maize seedlings. The results showed that whether inoculated with AMF or not, drought, high calcium and double stress decreased the biomass of maize seedlings. The colonization rate of the AMF to maize seedlings was following the sequence:control> drought> double stress> high Ca. Compared to the non-inoculated group under the same conditions,the total biomass of inoculated plants under control, drought stress and double stress was increased by26.3%,14%and8.2%respectively, while no significant effects were detected on the total biomass of inoculated seedlings under high Ca. Under drought and double stress. AMF inoculated maize seedlings could enhance the leaf water retention capacity through increasing leaf index. By decreasing the leaf biomass, leaf area, and specific leaf area to reduce the water evaporation, and increasing the root biomass, the plant ability to obtain moisture and nutrients from soil was improved. In the meantime, under the stress of high calcium, although the AMF could improve the plant’s abilities to capture light by allocating more biomass on their leaves, and increasing leaf area and specific leaf area, the inoculation was not conducive to a long-term survival and development of maize seedlings.2Effects of AMF on the roots characteristics, and the water absorption and utilization of maize seedlingsThe results showed that compared to the non-inoculated group under the same conditions, the root volume, water absorption and water use efficiency of inoculated maize seedlings under drought stress and double stress was slightly increased, while the proportion of root (D<0.2mm) was slightly decreased. However, these were all slightly decreased under high Ca stress. On the other hand, within the inoculated maize seedlings under drought stress, the plant’s root volume, and water use efficiency were significantly increased, while the proportion of fine root was significantly decreased. Within the inoculated maize seedlings under high Ca stress, the root volume and water absorption were significantly decreased. However, within the inoculated maize seedlings under double stress, the total root length, root volume, root surface area, water absorption and water use efficiency were significantly increased. Therefore, the regulation strategies of AMF on maize seedlings to different stresses in terms of root characteristics, water absorption and utilization were not completely consistent.3Effects of AMF on photosynthetic characteristics of maize seedlingsThe results showed that compared to the control group, the net photosynthetic rate (Pn) of the seedlings was decreased in all the three treatments, respectively. Additionally, compared to the non-inoculated group under the same conditions, the chlorophyll content, transpiration rate (Tr), maximum photochemical efficiency of the maize seedlings were increased slightly under drought and double stress. In the meantime, under high Ca conditions, the AMF inoculated seedlings showed significantly higher chlorophyll content and maximum photochemical efficiency, while there was no significant increase found in terms of the plant’s Tr. Both of the interaction of AMF and drought, and AMF and double stress can significantly affect the plant’s Pn, which compared with the non-significant effect under AMF and high Ca conditions. This research demonstrated that AMF can enhance the photosynthesis ability of maize seedlings through increasing chlorophyll content, photochemical efficiency and stomatal conductance.4Effects of AMF on the absorption, accumulation and distribution of phosphorus in maize seedlingsThe results showed that under drought stress, AMF can promote the P absorption and transfer in the maize roots, to increase the accumulation of P in the plant’s root, stem, and leaf. Under the stress of high calcium and double stress respectively, no significant effect of AMF on the P absorption in the plant’s root was found, which can help accumulate more P into the roots of the maize seedlings. Therefore, the increase of P accumulation and allocation in maize root can improve its adaptivity to the drought, high calcium and double stress in karst areas.5Effects of AMF on the absorption, accumulation and distribution of carbon and nitrogen in maize seedlingsThe results showed that whether inoculated with AMF or not, high calcium and double stress significantly decreased the total absorption of carbon and nitrogen in maize seedlings. Compared to the non-inoculated group under the same conditions, the total absorption of carbon and nitrogen were slightly increased, while that under high Ca stress was slightly decreased. However, under double stress, C uptake showed an increasing trend, while no significant effect was detected in terms of N absorption. On the other hand, compared to the non-inoculated seedlings, the C and N accumulation and distribution in the maize root were slightly increased under drought and double stress. Under the high Ca conditions, the inoculated seedlings showed decreasing trends in terms of C and N accumulation in the plant’s root, stem and leaf, while the allocation of C and N in the root was increased non-significantly. Due to the increased accumulation and distribution of C and N in the root can improve the physiological function of plant root, the AMF can improve the adaptability of maize in karst areas through increasing its root C and N accumulation and allocation.6Effects of AMF on the metabolism of maize seedlingsThe results showed that compared to the non-inoculated group under the same conditions, no significant difference was found in terms of the contents of MDA, proline, soluble sugar, and soluble protein between the maize seedlings under high Ca stress and corresponding controls. In the meantime, under drought stress, the contents of MDA and soluble protein in inoculated seedlings were significantly decreased, while that of proline and soluble sugar was significantly increased. However, under the double stress, the contents of MDA, soluble protein, and soluble sugar were significantly increased, while that of proline was significantly decreased. Therefore, the effects of AMF on the metabolism of maize seedlings were not completely consistent, and there were correlations between these metabolic substances.Above all, drought, high calcium and double stress had adverse effect on the growth of maize seedlings. The use of AMF may improve the adaptability of maize seedlings to different stresses in the karst areas. However, AMF showed various ecological effects on maize seedlings in different karst environments. The AMF was found to exert similar effects on the seedlings under the conditions of drought and double stress. |
PDF Full Text Request