Sobrado M A, Turner Neil C
Department of Environmental Biology, Research School of Biological Sciences, Australian National University, G.P.O. Box 475, 2601, Canberra, A.C.T., Australia.
Dryland Crops and Soils Research Program, CSIRO, Private Bag, P.O., 6014, Wembley, W.A., Australia.
Oecologia. 1986 May;69(2):181-187. doi: 10.1007/BF00377619.
This study reports on the effects of water deficits on photosynthesis, plant growth and carbon allocation in the wild sunflower Helianthus petiolaris and in the cultivated sunflower Helianthus annuus grown under controlled conditions in the glasshouse. Water deficits reduced the rate of net photosynthesis and the dry weight of leaves, stems, roots and reproductive parts in both species. The root-to-shoot ratio of about 0.05 in H. petiolaris was lower than the root-to-shoot ratio of about 0.15 in H. annuus. Water stress did not affect the root-to-shoot ratio, but increased the percentage of roots at depth in H. annuus. The decrease in growth induced by water deficits was a consequence of a reduction in both leaf area production and net photosynthesis. Flowering occurred earlier in H. petiolaris than in H. annuus with a consequent earlier allocation of carbon to reproductive parts in the wild compared to the cultivated sunflower. The time to budding and flowering of either species was not altered by mild water stress, but was delayed by severe water deficits. During mild water stress carbon allocation to stems decreased, but that to reproductive parts increased. When plants were severely stressed and then rewatered the proportion af carbon allocated to leaves increased and the proportion allocated to stems decreased when compared to unstressed plants. The adaptative role of these features is discussed.
本研究报告了水分亏缺对野生向日葵（Helianthus petiolaris）和温室控制条件下种植的栽培向日葵（Helianthus annuus）光合作用、植物生长及碳分配的影响。水分亏缺降低了两个物种的净光合速率以及叶片、茎、根和生殖器官的干重。糙叶向日葵（H. petiolaris）的根冠比约为0.05，低于向日葵（H. annuus）约0.15的根冠比。水分胁迫并未影响根冠比，但增加了向日葵（H. annuus）深层根系的比例。水分亏缺导致的生长下降是叶面积产生和净光合作用降低的结果。糙叶向日葵（H. petiolaris）比向日葵（H. annuus）开花更早，因此与栽培向日葵相比，野生向日葵向生殖器官的碳分配更早。轻度水分胁迫未改变任一物种的现蕾和开花时间，但严重水分亏缺会使其延迟。在轻度水分胁迫期间，分配到茎的碳减少，但分配到生殖器官的碳增加。与未受胁迫的植株相比，当植株受到严重胁迫然后重新浇水时，分配到叶片的碳比例增加，分配到茎的碳比例减少。文中讨论了这些特征的适应作用。
