Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, 77843-2128, USA.
Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, 77843-2128, USA.
Sci Rep. 2021 Jan 8;11(1):46. doi: 10.1038/s41598-020-79975-8.
The stems of bioenergy sorghum hybrids at harvest are > 4 m long, contain > 40 internodes and account for ~ 80% of harvested biomass. In this study, bioenergy sorghum hybrids were grown at four planting densities (~ 20,000 to 132,000 plants/ha) under field conditions for 60 days to investigate the impact shading has on stem growth and biomass accumulation. Increased planting density induced a > 2-fold increase in sorghum internode length and a ~ 22% decrease in stem diameter, a typical shade avoidance response. Shade-induced internode elongation was due to an increase in cell length and number of cells spanning the length of internodes. SbGA3ox2 (Sobic.003G045900), a gene encoding the last step in GA biosynthesis, was expressed ~ 20-fold higher in leaf collar tissue of developing phytomers in plants grown at high vs. low density. Application of GA3 to bioenergy sorghum increased plant height, stem internode length, cell length and the number of cells spanning internodes. Prior research showed that sorghum plants lacking phytochrome B, a key photoreceptor involved in shade signaling, accumulated more GA1 and displayed shade avoidance phenotypes. These results are consistent with the hypothesis that increasing planting density induces expression of GA3-oxidase in leaf collar tissue, increasing synthesis of GA that stimulates internode elongation.
在收获时，生物能源高粱杂种的茎长超过 4 米，包含超过 40 个节间，占收获生物量的~80%。在这项研究中，生物能源高粱杂种在田间条件下以四种种植密度（约 20,000 至 132,000 株/公顷）种植 60 天，以研究遮荫对茎生长和生物量积累的影响。增加种植密度会导致高粱节间长度增加一倍以上，茎直径降低约 22%，这是典型的避荫反应。遮荫诱导的节间伸长是由于细胞长度和跨节间长度的细胞数量增加。SbGA3ox2（Sobic.003G045900），编码 GA 生物合成最后一步的基因，在高种植密度和低种植密度下生长的植物中，处于发育的小穗节间叶鞘组织中的表达水平高出约 20 倍。GA3 应用于生物能源高粱可增加株高、茎节间长度、细胞长度和跨节间细胞数量。先前的研究表明，缺乏参与遮荫信号的关键光受体-phytochrome B 的高粱植物积累了更多的 GA1，并表现出避荫表型。这些结果与以下假设一致，即增加种植密度会诱导叶鞘组织中 GA3-氧化酶的表达，增加 GA 的合成，从而刺激节间伸长。
