McDowell Susan C, Turner David P
Environmental Science Program, Oregon State University, 321 Richardson Hall, Corvallis, OR, 97331, USA.
Department of Forest Science, Oregon State University, Corvallis, OR, 97331, USA.
Oecologia. 2002 Oct;133(2):102-111. doi: 10.1007/s00442-002-1006-5. Epub 2002 Oct 1.
We quantified the physiological costs and the total amount of resources allocated to reproduction in two closely related species of Rubus, one of which is invasive. These two species share several morphological and life-history characteristics and grow together in the Pacific Northwestern United States. Reproductive effort was manipulated in canes of both species by removing flower buds. The non-invasive species, R. ursinus, exhibited significantly greater water stress in the reproductive canes, as indicated by lower leaf water potential (Ψ) and reduced stomatal conductance (g ). This species also showed a reduction in leaf nitrogen concentration ([N]) associated with reproduction. Combined, these factors led to reduced photosynthesis (A) on a diurnal basis, lower water-use efficiency as inferred from δC, and reduced photosynthetic capacity. All of these effects were more pronounced during the fruiting stage than in the flowering stage. The invasive species, R. discolor, showed no changes in water stress, [N], δC, or A associated with reproduction. A model was used to estimate total gross photosynthesis (A ) for reproductive and non-reproductive canes of both species over cane lifetime. Reproduction was associated with a greater decline in A for the non-invasive R. ursinus than for the invasive R. discolor. Although R. discolor allocated more resources directly to flowers and fruit than R. ursinus, the invasive species had significantly lower reproductive effort, or total amount of resources diverted from vegetative activity to reproduction, than the non-invasive species. By minimizing the reduction of photosynthesis associated with reproduction, this invasive species may be able to minimize the trade-offs commonly associated with reproduction.
我们对悬钩子属两个亲缘关系密切的物种（其中一个为入侵物种）用于繁殖的生理成本和资源总量进行了量化。这两个物种具有若干形态和生活史特征，且共同生长于美国西北部太平洋地区。通过去除花芽，对两个物种的茎进行繁殖投入的操控。非入侵物种加州黑莓（Rubus ursinus）的繁殖茎表现出显著更高的水分胁迫，较低的叶片水势（Ψ）和气孔导度（g）表明了这一点。该物种还表现出与繁殖相关的叶片氮浓度（[N]）降低。综合这些因素导致其日间光合作用（A）降低，基于δC推断的水分利用效率降低，以及光合能力下降。所有这些影响在结果期比开花期更为明显。入侵物种变色悬钩子（Rubus discolor）在与繁殖相关的水分胁迫、[N]、δC或A方面未表现出变化。使用一个模型来估计两个物种繁殖茎和非繁殖茎在茎的整个生命周期内的总光合作用（A）。对于非入侵的加州黑莓，繁殖导致的A下降幅度大于入侵的变色悬钩子。尽管变色悬钩子比加州黑莓直接分配给花和果实的资源更多，但入侵物种的繁殖投入显著低于非入侵物种，即从营养活动转移到繁殖的资源总量更低。通过最小化与繁殖相关的光合作用降低，这种入侵物种可能能够最小化通常与繁殖相关的权衡。
