Effect of leaf removal on photosynthetically active radiation distribution in maize canopy and stalk strength

The objectives of this study were to determine how the distribution of photosynthetically active radiation （PAR） in a maize canopy affected basal internode strength and stalk lodging. The distributions of PAR within the canopies of two maize cultivars （Zhongdan 909 and Xinyu 41） were altered by removing whole leaves or half leaves in different canopy layers. The results showed that removing whole leaves or half leaves above the three-ear-leaves （RAE and RAE/2） at flowering sig- nificantly increased. PAR at the ear and interception of PAR （IPAR） from the ear to middle of the ear and soil surface. These changes increased the structural carbohydrate content and rind penetration strength （RPS） of the third basal internode by 5.4-11.6% and reduced lodging by 4.2-7.8%. Removal of the first three leaves below the three-ear-leaves （RBE） before flowering significantly reduced IPAR from the ear to half way below the ear. This reduced the structural carbohydrate con- tent and the RPS of the third basal internode by 9.1-17.4% and increased lodging by 7.0-11.2%. Removal of the three lowest green leaves （RB） in the canopy before flowering increased PAR at the bottom of the canopy, but had no effect on the structural carbohydrate content of the basal internode, the RPS, and the lodging rate. Overall, the results indicated that the key factors affecting the basal internode strength formation and lodging were PAR at the ear and IPAR from the ear to halfway below the ear. Increasing PAR at the ear and IPAR from the ear to halfway below the ear could enhance lodging resistance by increasing the structural carbohydrate content and mechanical strength of the basal internode.

Effects of leaf removal and cluster thinning on berry quality of Vitis vinifera cultivars in the region of Weibei Dryland in China

Leaf removal and cluster thinning were carried out prior to veraison to evaluate the effects on berry quality of two Vitis vinifera cultivars（Cabernet Sauvignon and Ugni Blanc） in the Weibei Dryland of China in 2013 and 2014, and comprehensive analysis of the chemical and volatile composition in berries was performed. The results showed that content of reducing sugar in both varieties was not affected while total acid was generally decreased by leaf removal and cluster thinning. The pH of berry juice was correspondingly higher in most treatment groups. Meanwhile, promoting effects on accumulation of total phenols, tannin in both varieties and total anthocyanins in Cabernet Sauvignon were found. As for monomeric anthocyanins, percentage of malvidin and its derivatives was decreased by leaf removal and cluster thinning. Besides, cinnamylated anthocyanins decreased with the intensity of cluster thinning. The accumulation of non-anthocyanin phenolics was similarly affected in the two varieties. Notably, cluster thinning was more effective on enhancing the phenolics content than leaf removal. The combination of middle level of leaf removal and cluster thinning was the most favor to the accumulation of phenolic acids. Furthermore, cluster thinning could also significantly enhance the synthesis of flavanols and stilbenes. Lastly, content and variety of aroma compounds in both grape varieties were also significantly affected by the treatments. The results provided a theoretical basis for a combination of leaf removal and cluster thinning to improve quality of grapes and wines.

Effect of Leaf Removal on Grapes of Cabernet Sauvignon and Sangiovese Cultivated in Different Italian Environments

Leaf removal is a farming practice that can affect must and grape quality; it is closely related to the meteorological conditions of the year and the climate of the area. The present study aims to analyse the effects of different types of defoliation, all conducted at veraison and removing 5-6 basal leaves. The trial provided four tests： leaf removal only on the east side, only on the west side, total defoliation （both sides）, and a non-defoliated treatment （control test）. Two different cultivars, the Sangiovese and the Cabernet Sauvignon, were studied in five different Italian environments： Puegnago （BS）, Scansano （GR）, Bolgheri （LI）, Brisighella （RA）, and Montefalco （PG）. The trial was repeated four times, once per year for the successive years 2007, 2008, 2009, and 2010. The years differed mainly with regard to the total rainfall; because of the variability of the years, different results, both for the same cultivar and between the cultivars, were observed. The differences existing between these two varieties and among the different environments led to different reactions to defoliation, especially concerning the analytical parameters of musts and grapes.