Pruning Effects On Sap Flow And Transportation Assignment Of Photosynthates In Grapevine

In cultivated grapevines, pruning at different locations along the shoot is a normal part ofviticulture, but it may lead to wedge-shaped organization and tylose formation in vessels nearcuts. These physical damages can profoundly affect the transportation capacity of vessel andsieve tube. Reasonable pruning can improve the adaptability of grapevines to environmentand grape quality. However, research of pruning effects on physiological activities of vine isquite few. We have conducted a systematical research on transport and distribution of water,as well as photosynthate during pruning period, using wine grape varieties.1. The results showed that tyloses at the nodes closest to the trunk developed rapidly; andtylose development initiated at the time when the size of vessel-ray pit was longer than that ofparenchyma cell. In current-year shoots, tyloses were formed in up to87%of vessels and40%of the vessels were completely blocked by tyloses. In wound-induced perennial shoots,the percentage was64%and30%, respectively.Tylose formation in functional vessels limited the water transport efficiency (the largestwas21.1%). When vessels were blocked partly or completely by tyloses, new onesdifferentiate to restore the water transport efficiency.2. Perennial cordon length is inversely proportional to sap flow of shoot, so the width ofsap flow is linear to time, that is to say, sap flow has a quick change with time. Induced by thedecrease in stomatal conductance, the diurnal variation of the photosynthetic rate (Pn) wasobvious ‘midday depression of photosynthesis’. The diurnal change of Pn or sugar unloadingis a typical bimodal curve, and the first peak was much higher than that of the second. Therewas no obvious difference among Pn or sugar unloadings of shoots with increasing watertransport distance. With the perennial cordon was longer, there was no obvious differenceamong Pn of different shoots, but the sugar unloadings significantly decreased (P<0.05).After pruning, the emergence and development of tylose in current-year shoot was morerapidly than the perennial cordon. Finally, the partly and completely blocked vessels by tylosein the current-year shoots was65%and30%, respectively, those were80%and35%in theperennial cordon.Based on above analysis and research, we propose a grape pruning management,"minimal pruning principle": when pruning, without influence to the normal production case of grape, the number of cuts and perennial section should be reduced as much as possible toprevent the perennnial section elongation.3. Growth rate and increment of current-year shoot were gradually decreased withincreasing the distance of water transport in development stage. Leaf was continuously grewand developed before veraison stage, chlorophyll content was continuously increasing inleaves of different shoots, while the chlorophyll content was continuously decreasing with theleaf senescence. The contents of total water, free water and dry matter, and the plasticity ofwater saturation deficit of leaf were small, and there was no significant difference amongleaves of different shoots. While, the plasticity of water potential, bound water content,bound/free water, leaf area and specific leaf area was large, and they were continuouslyincreasing with the increase of water transport distance, and even showed statisticallysignificant differences in different treatments. For different shoots, specific leaf weight andstomatal density increased gradually, but stomatal length decreased gradually. The differencebetween stomatal density and stomatal length were significant, but it was not significantbetween leaf thickness and stomtal width.The fruit growth curve of length was ‘double-S’ curve, there was no significantdifference. Sugar unloading and fruit fresh weight were both decreased gradually with theincrease of water transport distance. But the trend of berry in current-year shoot1,4and7was not obvious; the sugar unloading rate of berry in current-year shoot1was significantlylarger than that of current-year shoot7. Results showed significant difference for single fruitfresh weight, but not for the single fruit fry weight.Water transport distance was inversely proportional to shoot maturity, growth vigor andxylem width; and proportional to vessel density and vessel length. The relative grooming rateof vessel was continuously increasing in current-year shoot1,4and7, and the values were3.12,3.40and6.72, respectively. The results showed that vessel density, vessel width, xylemwidth and relative grooming rate of vessel was significantly different.4. The results showed that, the diurnal variation of the photosynthetic rate (Pn) sugarunloading rate is a typical bimodal curve, the diurnal variation of (Pn) demonstrated obvious‘midday depression’, meanwhile, they did not synchronize.With the rise of fruit setting position, sap flow rate and sugar phloem unloading ofdifferent shoots from the Guyot training system were both lower than that of Crawled CordonTraining (CCT), while the Pn has not the trend. With the increase of water transport distance,the Pn, sap flow and sugar phloem unloading of different shoot of the Guyot training systemgradually decreased. The perennial cordon of CCT grew many fibrous roots, and the growthand development of grape berry were uniform in different shoots, the trend of Pn, sap flowand sugar unloading was also uniform when compared with those in grape berries of different shoots.5. CCT shaping method avoided the unmounting in winter and mounting in spring, as aresult it was found easy for mechanized operations. Compared with Multiple main vinefan-training (MVF) and Cordon-training (CT), single worker’s labour time per667.7m2fromwinter pruning to spring unearthing in CCT was decreased37.50%and27.08%, respectively.The contents of soluble solid, reducing sugar and titratable acid in grape of the three shapingmethods had no significant difference. The stable ability of yield in CCT was significantlyhigher than MVF and CT. Moreover, the clusters’ infection rate of grape anthracnose, whiterot and grey mould were higher than those of the other two methods, but the berries’ infectionrate was significantly lower.Under the rational management measures, CCT shaping method can effectively controlpests and diseases, and could be a reasonable viticulture model with the objectives of highquality, stable yield, long-lived and artistic vine production in soil-burying over-winteringzone of arid and semiarid areas.