Hamido Said A, Ebel Robert C, Morgan Kelly T
Southwest Florida Research and Education Center, University of Florida, 2685 SR 29 N, Immokalee, FL 34142, USA.
Plants (Basel). 2019 Aug 23;8(9):298. doi: 10.3390/plants8090298.
The following study was conducted to determine the impact of frequent foliar Cu applications on water relations of Huanglongbing (HLB)-affected cv. 'Valencia'. HLB in Florida is putatively caused by Liberibacter asiaticus that is vectored by the Asian citrus psyllid. The experiment was conducted in a psyllid-free greenhouse with trees grown in Immokalee fine sand soil with the trees well-maintained to promote health. Cu was applied to the foliage at 0×, 0.5×, 1×, and 2× the commercially recommended rates, which were 0, 46, 92, and 184 mM, respectively, with applications made 3× in both 2016 and 2017. Previous studies indicate that HLB causes roots to decline before the canopy develops symptoms, which increases the ratio between the evaporative surface area of the canopy to the uptake surface area of roots and increases the hydraulic strain within the tree. In the current study, overall growth was suppressed substantially by HLB and Cu treatments but the ratio between evaporative surface area (leaf surface area) and the uptake surface area of roots (feeder root surface area) was not affected by either treatment. Stem water potential (Ψ), which was used as a measure of plant water deficits and the hydraulic strain within the tree, was significantly 13% lower for HLB-affected trees than the non-HLB controls but were not affected by Cu treatments. All Ψ measurements were in a range typical of well-watered trees conditions. Stomatal conductance (k) and root and soil resistances (R) were not affected by HLB and Cu. The results of this experiment suggest that tree leaf area and feeder roots are reduced when the trees are affected by HLB or are treated with foliar Cu applications such that plant water deficits are not significantly different over that of the controls.
开展了以下研究，以确定频繁叶面喷施铜对受黄龙病（HLB）影响的‘巴伦西亚’品种水分关系的影响。佛罗里达州的HLB据推测是由亚洲柑橘木虱传播的亚洲韧皮杆菌引起的。该实验在一个无木虱的温室中进行，树木种植在伊莫卡利细沙土中，并对树木进行精心养护以促进其健康生长。以商业推荐用量的0倍、0.5倍、1倍和2倍向叶片施用铜，分别为0、46、92和184 mM，在2016年和2017年各喷施3次。先前的研究表明，HLB会导致根系在树冠出现症状之前就衰退，这会增加树冠蒸发表面积与根系吸收表面积的比例，并增加树体内的水力应变。在本研究中，HLB和铜处理均显著抑制了整体生长，但蒸发表面积（叶表面积）与根系吸收表面积（须根表面积）的比例不受任何一种处理的影响。茎水势（Ψ）被用作衡量植物水分亏缺和树体内水力应变的指标，受HLB影响的树木的茎水势比未受HLB影响的对照显著低13%，但不受铜处理的影响。所有Ψ测量值都在水分充足的树木的典型范围内。气孔导度（k）以及根和土壤阻力（R）不受HLB和铜的影响。该实验结果表明，当树木受到HLB影响或进行叶面喷施铜处理时，树叶面积和须根会减少，因此植物水分亏缺与对照相比没有显著差异。
