Preliminary Researches On Highly Effective Pathway Of AmmoniaAssimilation And Its Relation To Surcrose Metabolism In Sugar Beet

The studies on changes of Nitrate Reductase(NR),Glutamina Synthetase(GS) and Sucrose Synthetase(SS) activity and nitrogen ucrose metabolism products content were conducted in root and leaf blade of sugar beet of cultiver Tian Yan-7 under different nitrogen level, and different proportion of nitrate and ammonia nitrogen ,and different PH in nutritious water culture and field experiment during the whole period of sugar beet growth in 1999. At the same time, root yield ,sugar content and sugar production were also analyzed. The objectives of this study were to preliminarily probe the most suitable condition of highly effective pathway of ammonia assimilation and 55 synthesis activity, and performe the effective sucrose accumulation in the lowest consumption of carbon. .The results could be drawn as follows: Under the condition of nutritious water, NR, GS, and 55 changed regularly. NR showed one curve of two peaks curve regularly: the peaks in the foliage formation period and the trough in the sugar accumulation stage respectively. GS changed according to one peak curve with the peak in the initial stage of sugar growth, slightly later than NR peak. 55 synthesis activity in leaf blade kept increasing gradually from the seedling stage, while SS decomposition activity present in single peak curve; while keeping rather high enzyme activities. 55 decomposition activity in root began to decline in the sugar accumulation period while SS synthesis activity showed increasing trend all the time. 55 mainly played the roJe on decomposition in leaf blade and synthesis in root. Different factors affected NR,GS,SS differently. NRA,GSA, decomposition SSA increase gradually with the increase of NO;N amount ,while 55 synthesis activity declined gradually. NH _N enhanced gradually NRA,GSA, SSA with its amount was lower than 8mmolIL . NRA,GSA, decomposition SSA were affected by PH in the order : 7.0>7.5>7.8>6.5>6.2 , while synthesis SSA were affected by PH in the order :7.5>7.0>7.8>6.5>6.2. Nitrogen level affected enzyme activity , yield and sugar content in root. NRA,GSA, synthesis 55 were affected by nitrogen level applied in the order 16>25.6>6.4mmolIL , while decomposition SSA ascend with nitrogen level increasing. Root yield was affected by nitrogen level applied in the order : 16>25.6>6.4mmollL, and sugar content was affected by nitrogen level applied in the order 6.4>16>25.6mmol/L, and the same rule was found in field experiment. Different of rratio of NO; /NH4 affected enzyme activity and nitrogen ucrose metabolism products content, yield and sugar content in root. GSA and synthesis SSA were higher in nitrate and ammonia nitrogen than any single nitrogen form. The order was 1:1>4:1>1:4>0:1>1:0. Structure protein and root yield and sugar production was affected by different of rratio NO; /NH4 in the order:1:1>4:1>1:0>1:4>0:1, while a --NH2--N and glucose and fructose rose gradually with NH4 risen. On contrary ,sucrose declined gradually . It was suitable to root yield, sugar production that NH amount was lower than 8mmollL in nitrate and ammonia nitrogen. There were the clearly reciprocal effect on root yield,sugar content and sugar production in nitrate and ammonia nitrogen and PH . Contribution rate of root yield was in the order : NO3 N> NH4 N>PH, and contribution rate of sugar content was in the order : NH4 _N> NO3- N>PH, and contribution rate of sugar production was in the order: NO; N>PH> NO;N. Therefore, it is not only by directly applying NH4 N to stimulate GS activity to explore...