Chapin F S, Groves R H, Evans L T
Institute of Arctic Biology, University of Alaska Fairbanks, 99775-0180, Fairbanks, AK, USA.
Division of Plant Industry, CSIRO, G.P.O. Box 1600, 2601, Canberra, ACT, Australia.
Oecologia. 1989 Apr;79(1):96-105. doi: 10.1007/BF00378245.
Under favorable nutrition, accessions of the weedy barleygrass (Hordeum leporinum and H. glaucum) had a higher relative growth rate (RGR) than did accessions of cultivated barley (H. vulgare) or its wild progenitor (H. spontaneum). RGR was not positively correlated with the presumed level of soil fertility at the collection site of an accession either within or among species. RGR was reduced more strongly by low-P supply in the progenitor than in the crop or weed, indicating that selection of cultivars to grow in fertile soils had not reduced their potential to grow effectively under low-P conditions. Seed and embryo masses were more important than RGR in determining plant size. Relative differences among assessions in plant size declined with time, because (1) accessions with small seeds had a higher RGR, and (2) RGR of large-seeded accessions declined with time. Absolute growth rate correlated positively with leaf area and negatively with photosynthetic rate per unit leaf area. Under favorable nutrition, maximum photosynthetic rate correlated negatively with leaf length and therefore was higher in the weeds than in the crop or progenitor accessions. P absorption potential did not differ consistently among species but generally increased in response to P stress. Cultivars produced a few tall tillers, whereas weeds and progenitors produced many small tillers. The cultivar had a larger proportion of reproductive tillers, allocated a larger proportion of biomass to grain, and produced larger grains than did the weedy accession. By contrast, the weed began maturing seeds sooner, produced more reproductive tillers, and produced more grains per car and per plant than did the cultivar. The study suggests two major conclusions: (1) A low RGR is not an adaptation to low P supply in annual Hordeum species. (2) Seed size is the major determinant of early plant size between accessions in these Hordeum species under favorable nutrition. However, large seed size indirectly results in a low RGR because of the inverse relationship between plant size and RGR and results in a low photosynthetic rate because of the inverse relationship between leaf size and photosynthesis.
在营养条件适宜时，杂草型大麦草（野大麦和灰绿大麦）的材料比栽培大麦（普通大麦）或其野生祖先（野生二棱大麦）的材料具有更高的相对生长速率（RGR）。无论是在种内还是种间，RGR与某一材料采集地假定的土壤肥力水平均无正相关关系。与作物或杂草相比，低磷供应对祖先材料RGR的降低作用更强，这表明选择在肥沃土壤中生长的栽培品种并没有降低它们在低磷条件下有效生长的潜力。种子和胚的质量在决定植株大小方面比RGR更重要。不同材料间植株大小的相对差异随时间而减小，原因如下：（1）种子小的材料具有较高的RGR；（2）大粒种子材料的RGR随时间下降。绝对生长速率与叶面积呈正相关，与单位叶面积光合速率呈负相关。在营养条件适宜时，最大光合速率与叶长呈负相关，因此杂草的最大光合速率高于作物或祖先材料。不同物种间的磷吸收潜力没有一致的差异，但一般会因磷胁迫而增加。栽培品种产生少数高大的分蘖，而杂草和祖先材料产生许多小分蘖。栽培品种的生殖分蘖比例更大，分配到籽粒的生物量比例更大，产生的籽粒也比杂草型材料更大。相比之下，杂草比栽培品种更早开始种子成熟，产生更多的生殖分蘖，每穗和每株产生更多的籽粒。该研究提出了两个主要结论：（1）低RGR并非一年生大麦属物种对低磷供应的适应性表现。（2）在营养条件适宜时，种子大小是这些大麦属物种不同材料间早期植株大小的主要决定因素。然而，由于植株大小与RGR之间呈反比关系，大种子大小间接导致低RGR，又由于叶大小与光合作用之间呈反比关系，导致光合速率较低。
