The effect of frost protection measuries on the physiology and growth of Citrus sinensis trees
1994
Mejdoub, M.
Leaf length (L) and width (W) were used to estimate leaf area (LA) of Citrus sinensis (L.) Osbeck nondestructively. The following equations: LA=-0.33+0.66LxW (R2=96.8,+ 1.07cm2), LA=1.00+0.62LxW (R2=97.0,+1.07cm2), LA=0.14+0.58LxW (R2=97.7+0.067cm2) can be used to accurately estimate leaf area of old, new, and newly expanded leaves, respectively. The effects (either positive or phytotoxic) of the application of two plant protection products, i.e. a copper hydroxide and a mixture of copper hydroxide and a fungicide (mancozeb), in conjunction with or without the concomitant operation of a wind machine on physiological characteristics of Citrus sinensis trees were evaluated. The combined effect of the mixture of copper hydroxide and mancozeb with the operation of a wind machine was an increase in leaf length, width, area, dry weight, thickness, specific leaf weight, and chlorophyll content, whether expressed on an area or dry weight basis. The positive effect of the copper hydroxide application on leaf growth was limited in time as it lasted for approximately three months after a middle winter application. Thereafter leaves showed phytotoxicity symptoms that may be due to the accumulation of excess copper. Some leaf shedding occurred, resulting in lower leaf area index in the copper hydroxide treated trees. However, this effect was widthdrawn during spring and both plant protection products in either grove promoted a significant increase in new growth (leaf expansion). The mean foliage inclination angle, which measures the foliage orientation, was not affected by chemical applications or by operating a wind machine. The values ranged from 51 to 56 in the grove deprived of a wind machine and from 51 to 57 in the grove deprived of a wind machine, confirming that in citrus the leaves are predominately vertical.
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