Various distances and orientations influenced the branching traits of Dendrocalamus minor var. amoenus in Dongshan Island, China

The application of biochar is mostly used to improve soil fertility, water retention capacity and nutrient uptake. The present study was conducted in order to study the impact of biochar at water deficiency conditions on the physiological and biochemical processes of Medicago ciliaris seedlings. Seedlings were cultivated under greenhouse conditions in pots filled with a mixture of soil and sand mixed in the presence or absence of 2% biochar. Plants of uniform size were subjected after a pretreatment phase (72 days) either to low (36% water holding capacity, water potential low) or high soil water potential (60% water holding capacity, water potential high). Pots were weighed every day to control and maintain a stable water holding capacity. In Medicago ciliaris, drought led to a significant reduction in plant growth and an increase in the root/shoot ratio. The growth response was accompanied by a decreased stomatal conductance and a reduction of the net CO2 assimilation rate and water use efficiency. The associated higher risk of ROS production was indicated by a high level of lipid peroxidation, high antioxidant activities and high proline accumulation. Soil amendment with biochar enhanced the growth significantly and supported the photosynthetic apparatus of Medicago ciliaris species by boosting chlorophyll content and Anet both under well and insufficient watered plants and water use efficiency in case of water shortage. This increase of water use efficiency was correlated with the biochar-mediated decrease of the MDA and proline contents in the leaves buffering the impact of drought on photosynthetic apparatus by increasing the activity of enzymatic antioxidants SOD, APX, GPOX and GR and non-enzymatic antioxidants, such as AsA and DHAsA, giving the overall picture of a moderate stress response. These results confirmed the hypothesis that biochar application significantly reduces both the degree of stress and the negative impact of oxidative stress on Medicago ciliaris plants. These results implied that this species could be suitable as a cash pasture plant in the development of agriculture on dry wasteland in a future world of water shortages.

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Impact of Biochar Application at Water Shortage on Biochemical and Physiological Processes in Medicago ciliaris

Dendrocalamus minor var. amoenus was analyzed for physiological and proteomic responses under drought stress. The adverse effects of drought on D. minor var. amoenus were primarily affected by gas exchange attributes such as photosynthesis (Pn), stomatal conductance (Gs), and transpiration rate (Tr) decreased as drought intensity increased. Among chlorophyll fluorescence parameters, actual photochemical efficiency of PSII (ΦPSII), electron transport rate (ETR), and non-photochemical quenching (qN) also decreased under increasing drought stress throughout the natural dehydration process (15-30 days). Moreover, superoxide dismutase (SOD) and catalase (CAT) levels increased significantly when subjected to short drought event and then decreased rapidly under severe drought stress. Using twodimensional gel electrophoresis (2-DE), we detected more than 500 protein spots; 41 significant differentially expressed protein spots were uncovered under drought stress. Following matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) identification and BLAST of these 41 proteins spots to an NCBI or Uniprot database, 33 differential protein spots were identified. In addition to determining a suitable protocol for protein extraction from D. minor var. amoenus (or other bamboo species), this study provides important information on signal transduction pathway changes under drought stress for exploring drought resistance candidate genes in bamboo species.

Y.S. Zheng

Papers

Physiological and proteomic responses of dendrocalamus minor var. amoenus (ghost bamboo) under drought stress