Photochemistry, remotely sensed physiological reflectance index and de-epoxidation state of the xanthophyll cycle in Quercus coccifera under intense drought

Quercus coccifera L. is a Mediterranean sclerophyllous shrub with a high capacity to resist intense drought stress. Therefore, it could be used in the study of physiological changes suffered by plants at very low water potentials. A remote sensing sensor was used to measure continuously the physiological reflectance index (PRI; defined as the changes in reflectance at 531 nm with respect to those at 570 nm; PRI = [(R531 − R570)/(R531 + R570)] at canopy level and under field conditions in an artificial carpet of seedlings of Q. coccifera during a drought cycle. Correlations between leaf level-measured chlorophyll fluorescence parameters as well as the de-epoxidation state of the xanthophyll cycle [(A + Z)/(V + A + Z)] and canopy level-measured PRI were reasonably good (R ² = 0.57–0.63, P < 0.01), and quite interesting for water stress remote sensing purposes. The instrument’s temporal resolution allowed us to follow the rapid response of PRI to changing photosynthetic active radiation, and to resolve, in response to cloud-induced changes in light intensity, a fast and a slow PRI component. We report the disappearance of the rapid one under conditions of intense drought in response to a sudden increase in light intensity. The underlying photoprotection mechanisms that Q. coccifera shows in response to intense drought stress periods seem to be related to the existence of a low intrathylakoid lumenal pH at the end of the drought cycle. Under intense drought, these mechanisms allow this species to avoid oxidative damage, which was evidenced by the maintenance of an unaltered photosynthetic pigment composition and constant photosystem II efficiency in the mornings. It is concluded that, contrary to early reports, PRI is a sensible, indirect, non-destructive water stress indicator, even in plants experiencing intense drought. Preliminary results of this work were presented at the 3rd International Workshop on Remote Sensing of Vegetation Fluorescence (February 2007, Florence, Italy).     

华北农业干旱监测与冬小麦估产研究

评估了基于植被光学厚度(VOD)和日光诱导叶绿素荧光(SIF)等植被广义光学特性构建的标准化植被指数(Z_VI)监测农业干旱的适用性;并采用VOD、SIF两种指数和土壤水分等环境变量的不同组合建立冬小麦估产的岭回归模型,以探究其对冬小麦产量的预报能力。结果表明：相较于Z_VOD,旬尺度Z_SIF对华北地区的农业干旱具有更好的监测能力,对重旱的正确检测率达到77%。Z_SIF能够有效反映干旱发生、发展直至减轻的演变过程,其低值区与站点记录的干旱空间分布相吻合。在华北地区南部,生长季C波段和Ku波段的VOD对冬小麦单产的预报能力优于SIF;利用VOD、SIF两种指数和环境变量的全变量模型取得了最好的估产精度,影响冬小麦产量估算精度的关键预测变量为生长高峰期的SIF。研究可为大范围农业干旱监测和粮食安全提供技术支持。     

作物缺水指数法的简化及在干旱遥感监测中的应用

从能量平衡原理出发,对潜在蒸散的计算进行了简化,从而对作物缺水指数法干旱遥感监测模型进行了简化、简化后的模型涉及因子减少,计算量明显降低,更接近于实际应用．利用该方法及NOAA/AVHRR卫星遥感资料和有关气象要素资料,对陕西省关中地区春季干旱进行了监测．结果表明,简化后的作物缺水指数法仍然充分考虑了下垫面的植被覆盖状况和地面风速、水汽压等气象要素,对该区春季干旱的监测效果好于使用植被供水指数法的监测效果．从简化后模型的计算量、时效响应和实际对比结果来看,该简化模型可以进行实际应用．另外,在计算过程中局部出现了CWSI>1的情况,这在实际中是不可能的,文中对此也进行了初步讨论．     

冬小麦高产高效栽培投资风险预测模拟

在产量形成规律及投入产出效益规律基础上,建立了冬小麦高产高效栽培投资风险预测模拟模型.并以Window XP为平台,采用VB(Visual Basic)语言编程,建立了相应的可视化模拟系统。通过模拟,生产者可以预测在当时的市场价格下小麦生产的投资风险大小,并预测生产的最大利润及小麦产量.模拟系统还可以用于决策部门对市场价格的宏观调控,如果希望增加农民收入,鼓励农民生产粮食,决策部门可以先定单位面积小麦生产利润值,通过模拟得适宜的肥粮价比,用来调控市场价格,     

Contributions of climatic and crop varietal changes to crop production in the North China Plain,since 1980s

The North China Plain (NCP) is the most important agricultural production area in China. Crop production in the NCP is sensitive to changes in both climate and management practices. While previous studies showed a negative impact of climatic change on crop yield since 1980s, the confounding effects of climatic and agronomic factors have not been separately investigated. This paper used 25 years of crop data from three locations (Nanyang, Zhengzhou and Luancheng) across the NCP, together with daily weather data and crop modeling, to analyse the contribution of changes in climatic and agronomic factors to changes in grain yields of wheat and maize. The results showed that the changes in climate were not uniform across the NCP and during different crop growth stages. Warming mainly occurred during the vegetative (preflowering) growth stage of wheat and maize, while there was a cooling trend or no significant change in temperatures during the postflowering stage of wheat (spring) or maize (autumn). If varietal effects were excluded, warming during vegetative stages would lead to a reduction in the length of the growing period for both crops, generally leading to a negative impact on crop production. However, autonomous adoption of new crop varieties in the NCP was able to compensate the negative impact of climatic change. For both wheat and maize, the varietal changes helped stabilize the length of preflowering period against the shortening effect of warming and, together with the slightly reduced temperature in the postflowering period, extend the length of the grain‐filling period. The combined effect led to increased wheat yield at Zhengzhou and Luancheng; increased maize yield at Nanyang and Luancheng; stabilized wheat yield at Nanyang, and a slight reduction in maize yield at Zhengzhou, compared with the yield change caused entirely by climatic change.     

河北省冬小麦丰产抗旱性表型鉴定指标分析

以河北省审定的85个冬小麦品种为材料,采用防雨棚春季干旱和露地灌溉2个处理,分别于开花期、成熟期调查株高等27个表型性状,分析了各表型性状与单株子粒产量的相关性。结果表明,单株成穗数等12个性状与单株子粒产量抗旱系数或抗旱指数呈显著或极显著相关;结合表型性状变异系数,明确了提高单株成穗数、穗粒数、灌溉条件下较长的旗叶长度和干旱条件下较短的旗叶长度是培育丰产抗旱小麦新品种的主攻方向;子粒比重、子粒长度及干旱条件下的结实率和每穗小穗数可作为河北省小麦种质资源丰产抗旱性的鉴定依据;河北省小麦品种丰产性高,而抗旱性尚需进一步改善。     

我国旱地春小麦产量及主要农艺指标的变异分析

采用4年、13个品种(系)、18个试点组成的全国旱地春小麦区域试验产量资料,通过联合方差分析和基因型及其与环境互作（GGE）双标图分析,研究了基因型、环境、基因型与环境互作效应（GEI）对产量变异的影响及品种的产量稳定性.结果表明：环境对产量变异的影响远大于基因型和GEI,环境引起的产量变异占87.5%～92.0%．互作因素中以地点×基因型的互作效应最大,基因型×年份的互作效应最小.我国旱地春小麦基因型多年多点的平均产量水平为2550 kg·hm^-2.产量三要素中,千粒重受环境的影响最小.影响产量变异的主要环境因子有：≥10 ℃年积温、生育期降雨量、平均气温、海拔、年降雨量和无霜期.产量与单位面积穗数（0.675^**）、穗粒数（0.581^**）、千粒重（0.456^**）呈极显著正相关,产量三要素间也呈正相关（0.244～0.480^**）,处于可同步提高范围.