Study On The Approaches And Plant Type For Super High-yielding Rice

hice plant type for super high yield playes the importam role in rice breedingand cultivation for super high yield as selecting traits and targets for cropmaneqement. The research was conduCted in the exPerimelltal Station of ChinaNational klce Research Institute in l998 and l999. With the tyPical high yieldingvarieties and hybrids in field and root box, a series of research was carried out ondifference in ratio of spikelat to leaf area among varieties and hybrids, contributionof different tillers to yield, characteriStics of leaf and its relation with photosynthesis,groWth and diStribution of roOt, importance of deep roOt, approach and plallt typefor super high yield.Research on relationship among area of 4 top leaves in stem and spikelatnumber per panicle, and ratio of spikelet number to leaf area indicated that there isthe positive relationship between leaf area and spikelet number per pbocle, andspikelet number per panicle and ratio of spikelet number to leaf area in all varieties.Raio of spikelet number to leaf area in different varieties ranges from 0.58 to l.03spikelet number/cm' with 78.4% difference. The raise of the ratio may increasethe increase in spikelet number per area with the same leaf area index.Leaf rolling index (Lm), photosynthesis in adaxial (upper) surface and abaxial(lower) leaf suffoce, leaf angle, leaf erecting index and light extinction coefficientwere stUdied at nowering and 2o days after fiowering with six rice hybrids in fieldconditions. Leaf rolling index (LAl) of flag leaf (from top) in 2 hybrids withhigher LRI reached 44%-47%, in 2 hybrids with medium LAl was l5%-l6%, in 2hybrids with low LAl was l0%-l l%. Ratio of abaxial photosynthesis to adaxial inflag leaves of hybrids with higher LRI ranged from l.l9 tO l.32 due to leafself shading impact on the adaxial surface, for hybrids with medium LAl rangedfrom 0.90 to l.02, for hybrids with low LRI ranged from 0.82 to 0.85. Comparedwith low LRI hybrids, the hybrids with higher and medium LRJ have smaller leafeqIe, higher leaf erecting index and Iow Iight endnCtion coefficient. Moderate Lmmay make the small an8le of leaf, hi8her leaf ereCting index and low li8htertinction coefficient, and raise photOsyathesis of abaxiaI and adaxiaI of leaf andlight permeation in canopyReseach on tillers wth different leaf eqes at panic1e initiation and itscontribution to yield shown that diffeence in perCenage of produCtive tillerbetween varieties resulted from small tiller with the late emefgence in higherposition in Stem. Vchety with higher percentage of produCtive tiller has less amoulltof this type of tiller In average, tiller with 4 leaf age and more, with 3 leaf age andwith 2 leaf age at panicle initiation contributed 96%, 3% and 0.2% of yieldrespectivelyResearch on root diStribution using the fOO box-Pin board mathod showed that52%ed3% of root biomass is distributed in the top 0l2cm of soil and 70%~79% inM4cm of soil. Xieyou 9308 with slower leaf senescence has higher rOO biomassand higher percentrse of deeper roOts. Root weight index of Xieyou 9308 belowsurface soil is much higher than that in other varieties. For horizntal diStribution,root biomass increases in the direction opposite to hill center with the increase ofsoil depth. RoOt weight index in suthee soil is much higher than that in subsoillayer, and gradually decreases with the increase of soil depth.The research on root grOwth using od box method indicated that rOO wtrightreached maximum at fiowering stage and then decreased. With the advance ofgrOed stage, percentag of deeP roots (20-45cm in soiI) increased. Root Weghtincreased at highest rate and deep roots formed during the period of tiller Stage topbocle iaitiation. With increased soil weight density below 20cm, roO weigh andpercentage of deep roots maredly decreased.Research by cutting fOOs at panicle initiation ryI) and flowering (FL) stapes inroo box indicated that comPared...