Ayala-Silva Tomas, Beyl Caula A
USDA-ARS Horticulture Research Station, National Germplasm Repository, Miami, FL 33158, USA.
Adv Space Res. 2005;35(2):305-17. doi: 10.1016/j.asr.2004.09.008.
In wheat (Triticum aestivum L.) plants, deficiency of an essential element may drastically affect growth, appearance, and most importantly yield. Wheat, the focus of this study, is one of the crops studied in the CELSS program. Information about nutrient deficiencies in crops grown in controlled environment is essential to optimize food productivity. The main objective of this study was to determine whether deficiency of Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca) and Magnesium (M) alters spectral reflectance properties of wheat leaves. Plants were grown in the greenhouse and growth chamber, in a modified Hoagland's nutrient solution. Spectral reflectance of fully expanded wheat leaves from 280 to 1100 nm, nutrient concentrations (N, P, K, and Ca) and chlorophyll (Chl) were determined when deficiency symptoms were first evident (approximately 6-7 weeks). Chlorophyll content and fresh and dry weight, were used to assess the severity of the nutrient stress. All nutrient deficiencies affected chlorophyll content and generally increased reflectance in the visible (VIS) 400-700 nm and infrared (IR) 700-1100 nm ranges. Magnesium and nitrogen deficiencies had the most pronounced effect on chlorophyll concentration height, and reflectance. All macronutrient deficiencies tested reduced chlorophyll concentration, increase reflectance in the visible range and caused a shift in the position of the red edge (the point of maximum slope on the reflectance spectrum of vegetation between red and near-infrared wavelengths) toward shorter or longer wavelengths; depending upon the element. In the greenhouse, N and Mg induced the greatest increase in reflectance of 33% and 25% in the VI range and 86% and 53% in the IR range, respectively. However, in the growth chamber, an increase of 97% and 25% occurred in the VI range, and 20% and 33% in the IR range, respectively. In the IR range in the growth chamber, P, K, and Ca deficiency caused a reduction in reflectance (412-770 nm). This research indicates that mineral deficiencies and reflectance are not specific to one environment and could have important implications for the design of CELSS in space, and perhaps the future of terrestrial agriculture.
在小麦（普通小麦）植株中，必需元素的缺乏可能会严重影响生长、外观，最重要的是影响产量。本研究的重点作物小麦是受控生态生命支持系统（CELSS）计划中研究的作物之一。了解在受控环境中种植的作物的养分缺乏情况对于优化粮食生产力至关重要。本研究的主要目的是确定氮（N）、磷（P）、钾（K）、钙（Ca）和镁（Mg）的缺乏是否会改变小麦叶片的光谱反射特性。植株在温室和生长室中，于改良的霍格兰营养液中生长。当缺乏症状首次显现（约6 - 7周）时，测定完全展开的小麦叶片在280至1100纳米的光谱反射率、养分浓度（N、P、K和Ca）以及叶绿素（Chl）。叶绿素含量以及鲜重和干重用于评估养分胁迫的严重程度。所有养分缺乏均影响叶绿素含量，并且通常会增加可见光（VIS）400 - 700纳米和红外（IR）700 - 1100纳米范围内的反射率。镁和氮的缺乏对叶绿素浓度高度和反射率的影响最为显著。所测试的所有大量元素缺乏均降低了叶绿素浓度，增加了可见光范围内的反射率，并导致红边（植被在红光和近红外波长之间的反射光谱上斜率最大的点）位置向更短或更长波长移动；这取决于元素。在温室中，氮和镁分别使可见光范围内的反射率最大增加33%和25%，红外范围内分别增加86%和53%。然而，在生长室中，可见光范围内分别增加97%和25%，红外范围内分别增加20%和33%。在生长室的红外范围内，磷、钾和钙的缺乏导致反射率降低（412 - 770纳米）。这项研究表明，矿物质缺乏和反射率并非特定于某一种环境，这可能对太空CELSS的设计以及或许陆地农业的未来具有重要意义。
