Some common staple roots and tubers (cassava, yam, sweet potato and yellow yam) were analyzed for selenium content level using hydride generation—atomic absorption spectrophotometry (HG-ASS) technique. Results for du...Some common staple roots and tubers (cassava, yam, sweet potato and yellow yam) were analyzed for selenium content level using hydride generation—atomic absorption spectrophotometry (HG-ASS) technique. Results for duplicate analysis revealed that sweet potato has the highest mean selenium content (19.2 ± 5.20 μg/kg), followed by yellow yam (18.3 ± 6.97 μg/kg), then yam (13.6 ± 7.12 μg/kg) and cassava the least (13.0 ± 5.84 μg/kg). In comparing our results with the literature values, most of the results obtained in this work such as <1.00, 1.09, 1.91, 2.35 and 11.0 μg/kg were lower while a few others like 52.6, 54.2, 72.3 and 81.8 μg/kg were higher than literature values. The variations could be due to the type of species/variety, geographical location, total selenium concentration in the soil and its bioavailability. In view of the importance of Se to human health and considering the levels found in the staples investigated, we recommend that sweet potato be popularized as a staple, much more than cassava as it is now the case in Central Nigeria.展开更多
Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this t...Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this tree has been problematic,which greatly hinders its utilization at a large scale.Cultivation difficulties of some tree species in the family Olacaceae have been attributed to their root hemiparasitic habit.Prompted by field observations and the taxonomic proximity of M.oleifera to root hemiparasites in Olacaceae,we hypothesized that tuberous structures observed on the roots of M.oleifera are parasitic organs known as haustoria.To test this hypothesis,we collected root samples from M.oleifera plants of various ages and growth conditions,investigated the morphological and anatomical features of tuberous structures and their connections to neighboring roots.Our analyses confirmed that M.oleifera are root hemiparasites.To the best of our knowledge,this is the first empirical report on root hemiparasitism in M.oleifera.Because life strategies of root hemiparasitic plants differ greatly from autotrophic plants,the root hemiparasitic habit needs to be taken into account for successful seedling regeneration of M.oleifera.This study establishes the foundation for investigations into a long-neglected but essential aspect in research of these highly valued tree species.展开更多
目前,菊芋机械化收获过程中的清选及输送等环节作业参数设定缺乏适用的理论依据,以收获期菊芋根-块茎为研究对象,基于离散元方法建立了一种能反映根须柔性和块茎脱落力学特性的粘结模型并对其相关参数进行了标定。首先通过物理试验确定...目前,菊芋机械化收获过程中的清选及输送等环节作业参数设定缺乏适用的理论依据,以收获期菊芋根-块茎为研究对象,基于离散元方法建立了一种能反映根须柔性和块茎脱落力学特性的粘结模型并对其相关参数进行了标定。首先通过物理试验确定了菊芋根-块茎本征参数、基本接触参数及相关力学参数,然后在此基础上利用Hertz-Mindlin with bonding V2接触模型构建了菊芋根-块茎粘结模型,并通过单因素试验和响应曲面试验,分别标定了菊芋根颗粒之间和根与块茎颗粒之间法向粘结刚度、切向粘结刚度、临界法向应力、临界切向应力等粘结模型参数。菊芋根须三点弯曲及根-块茎拉伸试验结果表明,根须弯曲弹性模量仿真结果与实际测量值相对误差为4.29%;菊芋根-块茎抗拉力仿真结果与实际测量值相对误差为7.72%;菊芋块茎脱落试验结果表明,仿真试验与菊芋收获机实际田间作业相比,滚筒筛转速对菊芋块茎脱落率影响趋势一致,筛内物料筛分规律相符。所构建的菊芋根-块茎模型可用于菊芋机械化收获相关环节的分析研究。展开更多
文摘Some common staple roots and tubers (cassava, yam, sweet potato and yellow yam) were analyzed for selenium content level using hydride generation—atomic absorption spectrophotometry (HG-ASS) technique. Results for duplicate analysis revealed that sweet potato has the highest mean selenium content (19.2 ± 5.20 μg/kg), followed by yellow yam (18.3 ± 6.97 μg/kg), then yam (13.6 ± 7.12 μg/kg) and cassava the least (13.0 ± 5.84 μg/kg). In comparing our results with the literature values, most of the results obtained in this work such as <1.00, 1.09, 1.91, 2.35 and 11.0 μg/kg were lower while a few others like 52.6, 54.2, 72.3 and 81.8 μg/kg were higher than literature values. The variations could be due to the type of species/variety, geographical location, total selenium concentration in the soil and its bioavailability. In view of the importance of Se to human health and considering the levels found in the staples investigated, we recommend that sweet potato be popularized as a staple, much more than cassava as it is now the case in Central Nigeria.
基金financially supported by funding for Airong Li from Yunnan Ten Thousand Talents Plan Young and Elite Talents Project (YNWR-QNBJ-2018-092)Youth Innovation Promotion Association of Chinese Academy of Sciences (2011276)+2 种基金Young Academic and Technical Leader Raising Foundation of Yunnan Province (2014HB047)funding for Yunju Li from Young Academic and Technical Leader Raising Foundation of Yunnan Province (2019HB060)Yunnan Science and Technology Innovation Team Program (Grant No. 2019HC015)
文摘Malania oleifera(Olacaceae)is a valued tree species,mostly because its seeds have high precious fatty acid content(particularly nervonic acid).However,seedling mortality rates are often high and regeneration of this tree has been problematic,which greatly hinders its utilization at a large scale.Cultivation difficulties of some tree species in the family Olacaceae have been attributed to their root hemiparasitic habit.Prompted by field observations and the taxonomic proximity of M.oleifera to root hemiparasites in Olacaceae,we hypothesized that tuberous structures observed on the roots of M.oleifera are parasitic organs known as haustoria.To test this hypothesis,we collected root samples from M.oleifera plants of various ages and growth conditions,investigated the morphological and anatomical features of tuberous structures and their connections to neighboring roots.Our analyses confirmed that M.oleifera are root hemiparasites.To the best of our knowledge,this is the first empirical report on root hemiparasitism in M.oleifera.Because life strategies of root hemiparasitic plants differ greatly from autotrophic plants,the root hemiparasitic habit needs to be taken into account for successful seedling regeneration of M.oleifera.This study establishes the foundation for investigations into a long-neglected but essential aspect in research of these highly valued tree species.
文摘目前,菊芋机械化收获过程中的清选及输送等环节作业参数设定缺乏适用的理论依据,以收获期菊芋根-块茎为研究对象,基于离散元方法建立了一种能反映根须柔性和块茎脱落力学特性的粘结模型并对其相关参数进行了标定。首先通过物理试验确定了菊芋根-块茎本征参数、基本接触参数及相关力学参数,然后在此基础上利用Hertz-Mindlin with bonding V2接触模型构建了菊芋根-块茎粘结模型,并通过单因素试验和响应曲面试验,分别标定了菊芋根颗粒之间和根与块茎颗粒之间法向粘结刚度、切向粘结刚度、临界法向应力、临界切向应力等粘结模型参数。菊芋根须三点弯曲及根-块茎拉伸试验结果表明,根须弯曲弹性模量仿真结果与实际测量值相对误差为4.29%;菊芋根-块茎抗拉力仿真结果与实际测量值相对误差为7.72%;菊芋块茎脱落试验结果表明,仿真试验与菊芋收获机实际田间作业相比,滚筒筛转速对菊芋块茎脱落率影响趋势一致,筛内物料筛分规律相符。所构建的菊芋根-块茎模型可用于菊芋机械化收获相关环节的分析研究。
