To understand the molecular responses of PC(Overexpressing the maize C4-pepc gene, which encodes phosphoenolpyruvate carboxylase(PEPC)), to drought stress at cell level, we analyzed changes in the levels of signaling molecules(hydrogen peroxide(H2O2), calcium ion(Ca2t), and nitric oxide(NO)) in suspension-cultured PC and wild-type(WT)rice(Oryza sativa L.) cell under drought stress induced by 20%polyethylene glycol 6000(PEG-6000). Results demonstrated that PC improved drought tolerance by enhancing antioxidant defense, retaining higher relative water content, survival percentages, and dry weight of cells. In addition, PEPC activity in PC under PEG treatment was strengthened by addition of H2O2 inhibitor, dimethylthiourea(DMTU) and NO synthesis inhibitor, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide(c PTIO), respectively, while that in PC was weakened by addition of free calcium chelator, ethylene glycol-bis(b-aminoethylether)-N,N,N0,N0-tetraacetic acid(EGTA)t calcium channel outflow inhibitor, ruthenium red(RR) t plasma membrane channel blocker La(NO3)3, but EGTA t RR did Reseanot. Results also showed that NO and Ca2 twas lying downstream of H2O2 in drought-induced signaling. Calcium ion was also involved in the expression of C4-pepc in PC. These results suggested that PC could improve oxidative tolerance in suspension-cultured cells and the acquisition of this tolerance required downregulation of H2O2 and the entry of extracellular Ca2 tinto cells across the plasma membrane for regulation of PEPC activity and C4-pepc expression.
以南粳49为材料，研究栽插苗数对超级稻冠层和产量的影响。结果表明，南粳49对栽插苗数有较宽的适应范围，在2～4株·穴-1的栽插苗数内，南粳49均可达到较高的产量，而5株·穴-1则产量显著降低。不同的栽插苗数，南粳49有不同适应调节方式：2株·穴-1的植株，可通过增加单株分蘖数、每穗总粒数和提高单叶光合能力，从而增加干物质累积而获得高产；3株·穴-1的植株，则通过增加群体叶面积等提高群体数量的方式，增加有效穗数，而获得高产；在4株·穴-1的植株，则通过增加叶面积指数，以及减少倒2叶的叶基角以增加群体中层截光率，而改善群体质量，从而达到高产。可见，南粳49是具有较强群体调控能力的超高产水稻品种类型，选择2株·穴-1的栽插苗数，产量可以达到（12.63±0.253） t · hm -2，而且可以减少用种量。
