Madhok O P, Walker R B
Botany Department, University of Washington, Seattle, Washington 98105.
Plant Physiol. 1969 Jul;44(7):1016-22. doi: 10.1104/pp.44.7.1016.
Helianthus annuus L., the common cultivated sunflower, and Helianthus bolanderi Gray subspecies exilis Heiser, a form endemic on serpentine soils, were grown in culture solutions with widely varying Mg levels. For comparable development, H. bolanderi exilis required higher levels of Mg in the solution than H. annuus, both in the range of visual deficiency symptoms and in higher ranges.With 0.5 mm Ca in the solutions, H. annuus reached a plateau in yield in the range of 0.25 to 2.0 mm Mg in the solution, then declined in weight markedly as Mg was increased further. This decline was probably caused by the marked "luxury" consumption of Mg. Conversely, H. bolanderi exilis increased steadily in yield as Mg was raised up to 10 mm and tolerated up to 50 mm Mg in the solution with only about 30% decline in yield. The increasing yield of H. bolanderi exilis in solutions of increasing Mg level is attributable to the steadily rising Mg content of the plants. A high level of external Mg is apparently needed to bring internal Mg to the sufficiency range. This characteristic of the species also serves to obviate luxury consumption of Mg, thus contributing to its tolerance of very high external levels of this ion.
普通栽培向日葵向日葵（Helianthus annuus L.）和蛇纹石土壤特有的一种形态——博兰德向日葵（Helianthus bolanderi Gray亚种exilis Heiser），在镁含量差异很大的培养液中培养。为了实现可比的生长发育，无论是在出现明显缺素症状的范围内还是在更高范围内，博兰德向日葵（Helianthus bolanderi exilis）在培养液中所需的镁水平都高于向日葵（Helianthus annuus）。当培养液中钙含量为0.5 mM时，向日葵（Helianthus annuus）在培养液镁含量为0.25至2.0 mM范围内产量达到平稳状态，之后随着镁含量进一步增加，重量显著下降。这种下降可能是由于明显的镁“奢侈性”消耗所致。相反，随着镁含量提高至10 mM，博兰德向日葵（Helianthus bolanderi exilis）产量稳步增加，并且在培养液镁含量高达50 mM时仍能耐受，产量仅下降约30%。随着培养液镁含量增加，博兰德向日葵（Helianthus bolanderi exilis）产量增加是因为植株中镁含量稳步上升。显然需要高水平的外部镁才能使内部镁含量达到充足范围。该物种的这一特性还避免了镁的奢侈性消耗，从而有助于其耐受这种离子的非常高的外部水平。
