甜菜碱在果树胁迫中的作用

甜菜碱是一种非毒性渗透调节物质,对维持逆境胁迫下果树的代谢和生存具有重要的生理意义,系统讨论了甜菜碱在植物胁迫条件下的作用机制。由于并非所有植物在胁迫条件下会产生内源甜菜碱,因此外源甜菜碱使植物获得抗性的研究受到广泛关注。现对不同途径添加外源甜菜碱在果树抗逆过程中所起的作用进行举例说明,试图为增强果树的抗逆性提供新的技术措施。     

绿盲蝽越冬卵在苹果园中的空间分布型及抽样技术

近年来绿盲蝽Apolygus lucorum已经逐渐发展成为果树上的重要害虫之一, 对其越冬卵在果树上的空间分布型进行探究具有重要意义?本研究利用6种聚集度指标?Iwao回归方程和Taylor幂法则分析了苹果园中绿盲蝽越冬卵的空间分布型, 同时对苹果园绿盲蝽越冬卵聚集的原因和最适理论抽样数进行了分析与计算?结果显示, 绿盲蝽越冬卵在苹果园呈聚集分布, 并且随着越冬卵密度的增加, 分布越聚集?绿盲蝽越冬卵的种群聚集是由其生活习性与周围环境共同引起的?运用绿盲蝽越冬卵空间分布型参数, 建立Iwao理论抽样数模型, 从而明确不同密度下绿盲蝽越冬卵的最适理论抽样数, 为今后绿盲蝽越冬卵在苹果园内密度的准确调查和种群密度的预测提供了理论依据?     

苹果树体磷素动态规律与施肥管理

以"富士"苹果树为试材,对果树体生物量和各器官及其皮层、木质部的磷含量和累积动态进行了研究,以期探讨果树磷素吸收、转运和分配规律.结果表明,3月26日至9月21日,树体生物量呈直线增加,果实采收后,生长缓慢,7月30日后,根系快速生长,植株、地上部及根系中磷累积迅速增加;枝、干和根系皮层内磷含量与累积7月30日最低,休眠期最高,皮层磷含量枝＞干＞根系;而木质部磷含量与累积4月30日达最低,木质部磷含量根系＞枝＞干;一年内,果树吸磷总量为28.72 kg/hm2,果实和叶片共带走磷素7.94 kg/hm2,7月30日至9月21日,吸收磷素18.32 kg/hm2,占吸收总量的63.8%,9月21日至1月15日,吸收磷素10.40 kg/hm2,占36.2%;苹果树(苹果产量48 t/hm2)年推荐施纯磷47.86 kg/hm2,果实收获后秋季基施磷17.33 kg/hm2,果实膨大期前追施磷30.53 kg/hm2.     

Drying half of the root-zone from mid fruit growth to maturity in ‘Hass’ avocado (Persea americana Mill.) trees for one season reduced fruit production in two years

We tested the effect of extended drying of half the root system on fruit yield and fruit Ca concentration, an indirect measure of fruit quality, in avocado (Persea americana Mill. cv Hass). In a field experiment on a sandy soil, withholding irrigation and plastic sheeting was used to dry the root-zone beneath the whole canopy (DD) or half the canopy (WD), compared with well-watered trees (WW). The irrigation water contained added nutrients and was slightly saline. Yield, shoot growth, leaf conductance, leaf and fruit water status and mineral concentrations of leaves and fruit were studied. The responses of treated trees were assessed in the following season during which normal irrigation practices were restored. With respect to yield, the WD treatment behaved the same as the DD treatment. It reduced yield by more than half and proportionately more than the reduction in water supply thus reducing irrigation efficiency. Re-watering did not restore yield of WD or DD-trees in the next season. The WD and DD treatments had no effect on the concentration of Ca in the fruit mesocarp and so are unlikely to affect fruit quality. The main impact of reduced water supply on the trees was fruit abscission and this was linked to dry soil around the roots rather than the water status of the leaves or fruits. We conclude that extended drying of half of the root-zone in one season reduced irrigation efficiency for two seasons by promoting the abscission of developing fruit to the same extent as occurred when the whole root system was exposed to extended drying.     

果树嫁接的优势及关键技术

嫁接是果树无性繁殖的方法之一,即采取优良品种植株上的枝或芽接到另一植株的适当部位,使两者结合而生成新的植株。文章总结了嫁接在保持品种优良形状、丰产和提高抗逆性等方面的优势,介绍了常见的三种嫁接方法(T型芽接、木质芽接、插皮舌接);在此基础上提出了选择合适嫁接材料、注意嫁接时间、选择合适的嫁接方法、选取合适的生长点等提高嫁接成活率的措施。     

利用动态阈值决策树分类的华北平原冬小麦动态监测

华北平原是中国最大的粮食生产基地,准确监测其冬小麦种植面积及其变化对粮食产量预测和国家粮食安全具有重要意义。然而,不同土地利用产品所估算的小麦面积、空间分布及其动态均存在较大分歧,不能有效反映出冬小麦的长期变化特征。该研究结合作物物候特征和已有小麦专题数据产品,首先构建动态阈值决策分类算法,以降低传统方法在阈值设定和样本筛选方面的不确定性;进而分析了2003—2022年华北平原区冬小麦播种面积的长期变化规律。结果表明：1）该研究提出的动态阈值决策分类算法能准确地提取冬小麦面积,平均总体精度为93.44%,且与统计数据具有较高的一致性;2）2003—2022年华北平原冬小麦种植面积整体呈上升趋势,不同地区变化类型差异较大;3）研究时段内,持续种植冬小麦的耕地面积仅占各年份种植范围总面积的5%,种植次数低于10 a的面积占比达55%;4）河北中南部、山东省西部和河南省中北部冬小麦种植面积相对稳定,京津冀地区以及山区冬小麦播种面积变化相对频繁。该研究可为大尺度冬小麦动态监测提供了新的方法视角,并对科学制定耕地调控策略具有重要意义。     

基于改进YOLOv7的杨梅树单木检测

为了快速检测和统计杨梅树的数量,该研究提出了一种基于改进YOLOv7的杨梅树单木检测模型：YOLOv7-ACGDmix。首先,对YOLOv7的可扩展高效长程注意力网络（extended-efficient long-range attention networks, E-ELAN）进行改进,通过融合兼具卷积和注意力机制优势的ACmix（a mixed model that enjoys the benefit of both self-attention and convolution）结构得到AC-E-ELAN模块,提升模型的学习和推理能力,引入可变形卷积（deformable convolutional networks version 2, DCNv2）结构得到DCNv2-E-ELAN模块,增强模型对不同尺寸目标的提取能力;其次,采用内容感知特征重组（content-aware reassembly of features, CARAFE）上采样模块,提高模型对重要特征的提取能力;然后,在主干和头部网络部分添加全局注意力机制（global-attention mechanism, GAM）,强化特征中的语义信息和位置信息,提高模型特征融合能力;最后,采用WIoU（wise intersection over union）损失函数减少因正负样本数据不平衡造成的干扰,增强模型的泛化性。在公开数据集上的试验结果表明,YOLOv7-ACGDmix模型的精确率达到89.1%,召回率达到89.0%,平均精度均值（mean average precision, mAP）达到95.1%,F₁-score达到89.0%,相比于原YOLOv7模型分别提高1.8、4.0、2.3和3.0个百分点。与Faster R-CNN、SSD、YOLOv8模型相比,改进模型的平均精度均值（mAP_0.5）分别提高了9.8、2.2、0.7个百分点。实地采集杨梅树样本数据的检测精确率87.3%、召回率85.7%。试验表明,改进模型为基于无人机影像的杨梅树单木检测提供了一种有效的解决方案,对果园精准管理的发展具有重要意义。     

Pear decline resistance in progenies of <Emphasis Type="Italic">Pyrus</Emphasis> taxa used as rootstocks

Progenies of 39 open-pollinated genotypes belonging to 26 Pyrus taxa were examined for pear decline resistance and pomological traits when used as rootstocks. Following graft inoculation and observation over 18 years, considerable differences in pear decline resistance between and within the progenies were observed. Not affected or little affected and moderately to severely affected trees were observed in all progenies. However, great quantitative differences among them were observed. In the progenies of about one third of the pollinated trees most of the individuals showed a high level of resistance to grafted trees. Significantly different from this group was another third of the progenies that mostly showed high susceptibility in grafted trees. Between these two groups there were progenies that statistically neither differed from the resistant nor from the susceptible group. These progenies were defined as moderately resistant. Significant differences in resistance were also observed between progenies of genotypes of the same species that originated from different locations. These data indicate segregation of the resistance trait and show that seedling progenies are unsuitable as rootstocks in commercial pear growing. Instead, careful selection of suitable genotypes for propagation is required. Great differences between and within the progenies examined were also observed in vigour and yield efficiency.     

稀土元素对林木的生理效应

在适宜条件下,稀土对林木许多生理功能都有积极作用。稀土在促进林木生长发育,增强营养水平,提高抗性等方面效果显著。稀土可能主要通过调节有关酶和内源激素水平及活性而发挥作用,其作用机理还有待于进一步研究。     

扬州城市道路部分绿化树种滞尘效应研究

以扬州市城区干道绿化树种为试材,研究了滞尘指标以及树种、地段、季节因素等对叶面滞尘效应评价的影响。结果表明:叶片滞尘量测定值在一定程度上可以反映客观环境空气中的颗粒物含量,以文昌路的最大、校园次之、公园最小,其与采样地点的影响密切相关;常绿灌木的叶片滞尘量较大,则表现为对地面粉尘的拦截能力强。因受树种单叶面积大小、树冠密集度、整株叶量多少和叶片组织结构等制约,各滞尘量指标间不尽一致。乔木树种中:单叶滞尘量(mg)与单位面积滞尘量(g/m2)反映一致,为广玉兰悬铃木银杏枫杨女贞香樟,干重滞尘量(mg/g)变化较大,为枫杨银杏悬铃木广玉兰女贞香樟;综合各项指标比较,以落叶树种的滞尘能力占优势,仅广玉兰的单位面积滞尘量表现最高。灌木树种中:单叶滞尘量(mg)、干重滞尘量(mg/g)均以珊瑚树最大,而单位面积滞尘量(g/m2)以小叶黄杨最大。叶片滞尘量的季节性变化与秸秆焚烧等大气污染的动态变化具有明显的相关性,其中:广玉兰以5月值最高,余皆以10月值最高。