Collins R P, Fothergill M, Macduff J H, Puzio S
Institute of Grassland and Environmental Research (IGER), Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK.
Ann Bot. 2003 Aug;92(2):247-58. doi: 10.1093/aob/mcg128.
The effects of nitrate (NO3-) supply on shoot morphology, vertical distribution of shoot and root biomass and total nitrogen (N) acquisition by two perennial ryegrass (Lolium perenne L.) cultivars (AberElan and Preference) and two white clover (Trifolium repens L.) cultivars (Grasslands Huia and AberHerald) were studied in flowing nutrient culture. Cultivars were grown from seed as monocultures and the clovers inoculated with Rhizobium. The 6-week measurement period began on day 34 (grasses) and day 56 (clovers) when the NO3- supply was adjusted to either 2 mmol m-3 (low nitrogen, LN) or 50 mmol m-3 (high nitrogen, HN). These treatments were subsequently maintained automatically. Plants were harvested at intervals to measure their morphology and N content. Cultivars of both species differed significantly in several aspects of their response to NO3- supply. In the grasses, the LN treatment increased the root : shoot ratio of AberElan but did not affect the distribution of root length in the root profile. In contrast, this treatment changed the root distribution of Preference compared with HN, resulting in a larger proportion of root length being distributed further down the root profile. The morphology of white clover Grasslands Huia was for the most part unaffected by the level of NO3- supply. In contrast, AberHerald exhibited different growth strategies, with LN plants increasing their stolon weight per unit length at the expense of leaf production, leaf area and stolon length, whereas HN plants showed reduced stolon thickness, greater leaf area production and stolon length per plant. Cultivars with different morphological/physiological strategies in response to NO3- supply may be of value in the construction of 'compatible mixtures' aimed at reducing oscillations in sward clover content by extending the range of conditions that allow balanced coexistence of species to occur.
在流动营养液培养中，研究了硝酸盐（NO₃⁻）供应对两个多年生黑麦草（Lolium perenne L.）品种（AberElan和Preference）以及两个白三叶草（Trifolium repens L.）品种（Grasslands Huia和AberHerald）地上部形态、地上部和根部生物量的垂直分布以及总氮（N）吸收的影响。品种以单作方式从种子开始种植，三叶草接种根瘤菌。6周的测量期从第34天（禾本科植物）和第56天（三叶草）开始，此时将NO₃⁻供应调整为2 mmol m⁻³（低氮，LN）或50 mmol m⁻³（高氮，HN）。这些处理随后自动维持。定期收获植物以测量其形态和氮含量。两个物种的品种在对NO₃⁻供应的响应的几个方面存在显著差异。在禾本科植物中，LN处理增加了AberElan的根冠比，但不影响根系剖面中根长的分布。相比之下，与HN处理相比，该处理改变了Preference的根系分布，导致更大比例的根长分布在根系剖面的更深处。白三叶草Grasslands Huia的形态在很大程度上不受NO₃⁻供应水平的影响。相比之下，AberHerald表现出不同的生长策略，LN处理的植株以叶片产量、叶面积和匍匐茎长度为代价增加了单位长度的匍匐茎重量，而HN处理的植株匍匐茎厚度减小，单株叶面积产量和匍匐茎长度增加。对NO₃⁻供应具有不同形态/生理策略的品种可能在构建“兼容混合物”中具有价值，旨在通过扩大允许物种平衡共存的条件范围来减少草地三叶草含量的波动。
