Am J Bot. 1997 Aug;84(8):1092.
Allocation trade-offs should be measured as opportunity costs, estimating what individuals sacrifice in one function by allocating to others. We investigated opportunity costs of male function in gynodioecious Phacelia linearis, asking whether nutrient limitation contributes to them. This hypothesis predicts that hermaphrodites experience greater nutrient stress than females, and that hermaphrodite disadvantages in production might decrease with nutrient supply. We cultivated hermaphrodites and females at two nutrient levels, scoring individuals for prereproductive leaf number at 5 wk, and biomass, nitrogen concentration, and fruit and seed production at 16 wk. Nutrient treatments caused final growth differences of two orders of magnitude. No gender difference appeared at 5 wk, but at 16 wk hermaphrodites produced less stem, leaf, and inflorescence biomass than females, and made fewer fruits. Hermaphrodites' shoot-size disadvantage was marginally significantly more severe at low nutrients than high nutrients. Significant gender x nutrient interactions for root fraction and whole-plant nitrogen concentration indicate greater nutrient stress in hermaphrodites than females. Hermaphrodites also acquired less total nitrogen than females. Nutrient limitation contributes to opportunity costs of male function, but there must be other contributors. Possibilities include limitations in other resources, gender effects on morphology, and genetic trade-offs not directly involving allocation or morphology.
分配权衡应该作为机会成本来衡量，通过将资源分配到其他功能上来估计个人在一个功能上的牺牲。我们研究了雌雄异株的 Phacelia linearis 中雄性功能的机会成本，探讨了营养限制是否会导致这种成本。该假设预测，雌雄同体比雌性经历更大的营养压力，并且随着营养供应的增加，雌雄同体在生产中的劣势可能会减少。我们在两种营养水平下培养雌雄同体和雌性个体，在 5 周时对个体的生殖前叶片数量进行评分，并在 16 周时对生物量、氮浓度以及果实和种子产量进行评分。营养处理导致最终生长差异达两个数量级。在 5 周时没有出现性别差异，但在 16 周时，雌雄同体的茎、叶和花序生物量比雌性少，果实也少。在低营养条件下，雌雄同体的枝条大小劣势比高营养条件下更为明显。根部分和整株植物氮浓度的显著性别 x 营养互作表明雌雄同体比雌性面临更大的营养压力。雌雄同体获得的总氮也比雌性少。营养限制导致雄性功能的机会成本增加，但肯定还有其他因素。可能包括其他资源的限制、形态对性别的影响以及不直接涉及分配或形态的遗传权衡。
