Selection For Turfgrass Roots Growth Promoters And The Study On Their Promoting Mechanism

Roots play an important role in turfgrass growth, development and the quality of turf. In practice, roots of turfgrass are not strong, deep and extensive, which is the biggest problem for turf application and leads to lower traffic tolerance and abiotic stress tolerance. Turfgrass includes warm season and cold season types. This research chose bahiagrass(Paspalum notatum) and tall fescue(Festuca arundinacea) as the warm and cold season turfgrass, respectively. The objective of this research was to find one substance which can promote warm or cold season turfgrass, select the best treatment concentration and time, and study on the mechanism of the promoter. The following were the results:The seven candidate chemicals, boron(B), calcium(Ca), iron(Fe), lanthanum(La), cerium(Ce), salicylic acid(SA) and melatonin(MLT), were selected for bahiagrass. The growth promotion effects were evaluated through root length, number and surface area. The results showed that the treatment of 0.3 μM La for 6 d promoted bahiagrass roots growth best. Based on this treatment, the mechanism of La promoting bahiagrass roots growth was explored from physiology and molecular level. The physiological test included La content, root vitality, cell wall components content, net photosynthetic rate, transpitation rate, stomata conductance, intercellular CO2 content, chlorophyll fluorescence parameters(Fv/Fm, Fv′/Fm′, ΦPSⅡ, q P, ETR), chlorophyll content, respiration intensity of bahiagrass roots, ascorbic acid oxidase(AAO) and polyphenol oxidase(PPO) activity of bahiagrass roots, subcellular distribution of mitochondria in bahiagrass root mature cell, IAA, ABA and GA contents of bahiagrass roots. High-throughput transcriptome sequencing and q RT-PCR were carried out at molecular level. The correlation index between the sequence and q RT-PCR results was 0.91. This documented that the results of transcriptome sequencing was dependable. Moreover, the sequence results were majorly consistent with the physiological results. Therefore, it was concluded that La could promote bahiagrass roots growth by enhancing root vitality, photosynthesis(PSⅡfunction and ETR), roots respiration(intensity and polyphenol oxidase(PPO) activity) and increasing the quantity of mitochondria in bahiagrass root mature cell, IAA contents.The five candidate chemicals for tall fescue were seleted, including trehalose(Tre), glycinebetaine(GB), spermidine(Spd), Brassinosteroide(BR) and Strigolactone(GR24). The candidate promote chemical was directly selected under drought stress.The growth promotion effects were evaluated through root total length, the main root elongation rate and root tips number. The results showed that the treatment of 0.3 m M trehalose for 12 d promoted tall fescue roots growth best.The mechanism of Tre promoting tall fescue roots growth was tested in normal and drought environment respectively. Root total length, main root elongation rate, root tips and internal structure of tall fescue root tip were measured in morphological test. The physiological test included soluble sugar contents(trehalose, glucose, fructose, sucrose) and hormones contents(JA, JA-ILE, OPDA, IAA, IAA-Asp, tran-ZR and GA). Molecular analysis included protein two-dimensional electrophoresis and q RT-PCR. The results of protein two-dimensional electrophoresis and q RT-PCR were consistent. This documented that the root growth regulation by Tre was consistent at transcription and post-translation level. Therefore, it was concluded that in normal environment, exogenous Tre could increase lateral root number by increasing soluble sugar content, tran-ZR content, defense and cell growth protein expression whereas under drought stress, exogenous Tre could improve the main root elongation by increasing root tip meristernatic zone, soluble sugar content, IAA content, energy metabolize and cell growth protein expression.Overall, it was concluded that 0.3 μM La could be regarded as root growth promoter for warm season turfgrass as it enhanced photosynthesis, respiration and IAA synthesis of bahiagrass; 0.3 m M Tre could be regarded as root growth promoter for cold season turfgrass through its increase of soluble sugar and hormones content, energy mechanism, defense, cell growth/division protein expression of tall fescue.