Photoassimilate partitioning in hypernodulation mutant of soybean (Glycine max (L.) Merr.) NOD1-3 and its parent williams in relation to nitrate inhibition of nodule growth

Nodule growth of a hypernodulating soybean (Glycine max (L.) Merr.) mutant line NOD1-3 was compared to that of its wild-type parent cv. Williams from 14 to 18 days after planting (DAP) in the absence of nitrate treatment (hereafter referred to as “0 mM treatment”) or with 5 mM nitrate treatment. The growth rate determined by increase in the diameter of the nodules was relatively lower in the mutant NOD1-3 than that of the parent Williams under nitrogen-free conditions (0 mM nitrate). The inhibition of nodule growth by 5 mM nitrate started at 1 d after the onset of the nitrate treatment in Williams, while the inhibition did not occur before the application of the nitrate treatment for 2 d in NOD1-3. The nodule growth was completely inhibited after 2 d in Williams and after 3 d in NOD1-3 during the 5 mM nitrate treatment period. After 4 d of 5 mM nitrate treatment, the nodule dry weight decreased by 22% in NOD1-3 and by 58% in Williams, respectively. The treatment with 5 mM nitrate decreased the acetylene reduction activity (ARA) in NOD1-3 by 60% per plant and by 50% per nodule g DW and these parameters were less sensitive to the treatment than those in Williams in which the inhibition rate was 90% per plant and 80% per nodule g DW. These results indicate that NOD1-3 is partially nitrate-tolerant in terms of individual nodule growth as well as total nodule dry weight and Nz fixation activity. A whole shoot of Williams and NOD1-3 plants was exposed to ¹⁴CO₂ for 120 min followed by 0 or 5 mM nitrate treatment for 2 d, and the partitioning of the photoassimilates among the organs was analyzed. Under 0 mM nitrate treatment, the percentages of the distribution of ¹⁴C radioactivity between the nodules and roots were 63 and 37% in Williams and 89 and 11% in NOD1-3. Under the 5 mM nitrate conditions, the percentages of the distribution of ¹⁴C between the nodules and roots changed to 14 and 86% in Williams and 39 and 61% in NOD1-3, respectively. These results indicated that the hypernodulating mutant NOD1-3 supplied a larger amount of photoassimilates to the nodules than to the roots under nitrogen-free conditions, and that the nitrate depression of photoassimilate transport to the nodules was less sensitive than that of the parent line.     

超级杂交稻光合同化物的运转分配特性

采用盆栽法和14C-同位素示踪技术,以杂交稻组合汕优46为对照,研究了超级杂交稻组合"两优293"、"准两优527"的光合能力和光合同化物运转分配特性。结果表明,在不同生育期,两个超级杂交稻组合与对照组合汕优46相比,其单株同化14CO2的总量均显著高于对照,达到对照的1.49~1.96倍;14C-光合同化物最终分配至穗中的比例也较对照高,且其14C-光合同化物运输至穗中的速率也比对照快。表明超级杂交稻组合"两优293"、"准两优527"具有较强的光合同化物生产和运输能力。     

Translocation and distribution of assimilated carbon in peanut plant

An attempt was made to monitor ¹³C that had been photosynthetically assimilated in the foliage of the main stem and branches of peanut plant, as well as in a single leaf at different positions on a branch.

When the foliage of the main stem or branch was supplied with ¹³CO₂ for 8 h at the vegetative stage, ¹³C assimilated in the branches was detected in the roots and nodules in addition to the foliage immediately after the exposure, whereas when the main stem was supplied with ¹³CO₂, ¹³C was not detected in the roots and nodules immediately after ¹³CO₂ feeding. At the reproductive stage, ¹³C assimilated in the main stem or branch was found in the leaves, stems, fruit (shell, seed coat, and seed), roots, and nodules immediately after assimilation.

Photoassimilates from each leaf of the branch at the reproductive stage were exported to the fruit and leaves that were attached to the same branch. Namely, photoassimilates in the leaves of odd nodes were mainly translocated to the fruits attached to the first node, whereas such photoassimilates from the leaf of even nodes were mainly translocated to the fruit attached to the second node.

When the foliage of a branch had been fed ¹³CO₂ at the vegetative stage, the loss of the assimilated ¹³C by respiration was about 40% of the total assimilated ¹³C within 23 d and about 65% within 93 d after the exposure, and a small amount of photoassimilates was detected in the fruit. On the other hand, at the seed-filling stage, about 35% of the photoassimilates were utilized for seed growth within 10 d after the end of exposure.

These results suggest that in the peanut plant, the carbon source of nodules mainly depends on the branch, and the main stem plays an important role as carbon source for the fruit, that a sink organ for carbon is connected with a specific sources leaf by the vascular bundles, and that most of the carbon sources for the growth of peanut fruit depend on the photoassimilates at the reproductive stage.     

施硫对两种品质类型小麦光合物质积累与转运的影响

以豫麦34和豫麦50两个品质类型的冬小麦品种为材料,研究了不同施硫水平对其光合物质积累与转运和产量的影响。结果表明,施硫可以提高豫麦34花后20d内旗叶叶绿素含量和灌浆中后期的净光合速率,同时提高了豫麦50开花后的旗叶叶绿素含量和净光合速率。施硫处理不仅提高了两品种开花期营养器官干物质和氮素的积累量,并促进其向子粒的转运,使单茎子粒重和氮素积累量高于不施硫处理。,施S 20 kg/hm2 处理能明显提高两品种子粒产量,豫麦34和豫麦50分别比对照增产10.69%和9.78%,同时显著的提高了子粒蛋白质和淀粉含量。施S 100 kg/hm2处理的效果小于低量施硫（S 20 kg/hm2）处理。