At early stages of establishment of tropical plantation crops, inclusion of legume cover crops could reduce soil degradation due to erosion and nutrient leaching. As understory plants these cover crops receive limited irradiance and can be subjected to elevated CO₂ at ground level. A glasshouse experiment was undertaken to assess the effects of ambient (450 µmol mol⁻¹) and elevated (700 µmol mol⁻¹) levels of [CO₂] on growth, physiological changes and nutrient uptake of six perennial legume cover crops (Perennial Peanut, Ea-Ea, Mucuna, Pigeon pea, Lab lab, Cowpea) under low levels of photosynthetic photon flux density (PPFD; 100, 200, and 400 µmol m⁻² s⁻¹). Overall, total and root dry biomass, total root length, specific leaf area, and relative growth rates were significantly influenced by levels of [CO₂] and PPFD and cover crop species. With few exceptions, all the cover crops showed significant effects of [CO₂], PPFD, and species on net photosynthesis (P_N) and its components, such as stomatal conductance (gs) internal CO₂ conc. (Ci), and transpiration (E). Increasing [CO₂], from 450 to 700 μmol mol⁻¹ and increasing PPFD from 100 to 400 μmol ּm⁻² ּs⁻¹ increased P_N. Overall, the levels of [CO₂], PPFD and species significantly affected total water use efficiency (WUE_TOTAL), instantaneous water use efficiency (WUE_INST) and intrinsic water use efficiency (WUE_INTR). With some exceptions, increasing levels of [CO₂] and PPFD increased all the WUE parameters. Interspecific differences were observed with respect to macro-micro nutrient uptake and use efficiency. With a few exceptions, increasing levels of [CO₂] from 450 to 700 μmol mol⁻¹ and PPFD from 100 to 400 μmol m⁻² s⁻¹ increased nutrient use efficiency (NUE) of all nutrients by cover crop species.

中文翻译：

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低光照水平下的环境和升高 [CO2] 对热带多年生豆科覆盖作物的生长、生理和养分吸收的影响

在热带种植园作物种植的早期阶段，纳入豆类覆盖作物可以减少由于侵蚀和养分淋溶而导致的土壤退化。作为林下植物，这些覆盖作物接受的辐照度有限，并且可能会受到地面升高的 CO _{2的影响。}进行了温室实验，以评估环境（450 µmol mol ⁻¹）和升高（700 µmol mol ⁻¹）水平的[CO ₂ ]对六种多年生豆科覆盖作物（多年生花生）的生长、生理变化和养分吸收的影响。 、Ea-Ea、黧豆、木豆、实验室实验室、豇豆）在低水平的光合光子通量密度（PPFD；100、200和400 µmol m ^-2 s ^-1）下。总体而言，总和根干生物量、总根长、比叶面积和相对生长率受到[CO ₂ ]和PPFD水平以及覆盖作物种类的显着影响。除少数例外，所有覆盖作物均表现出 [CO ₂ ]、PPFD 和物种对净光合作用 ( P _N ) 及其组成部分（例如气孔导度 ( gs ) 内部 CO ₂浓度）的显着影响。( Ci )和蒸腾作用 ( E )。将[CO 2 _]从450增加到700 μmol mol ^-1并将PPFD从100增加到400 μmol ּm ^-2 ּs ^-1增加PN _{。总体而言，[CO 2} ]、PPFD和物种的水平显着影响总水分利用效率( WUE _TOTAL )、瞬时水分利用效率( WUE _INST )和内在水分利用效率( WUE _INTR )。除了一些例外，[CO ₂ ] 和 PPFD 水平的增加会增加所有WUE参数。在宏观-微观养分吸收和利用效率方面观察到种间差异。除少数例外，将[CO ₂ ]水平从450增加到700 μmol mol ^-1并将PPFD从100增加到400 μmol m ^-2 s ^-1提高了覆盖作物物种所有养分的养分利用效率（NUE）。