Primary Study On Fruit-drop Biological Reason Of Carya Illinoensis Of Mahan

Carya illinoensis(Wangench.)K.Koch is a woody oil tree in our country. To solve the physiologicalfruit drop on pecan of Mahan and acquire high quality and high yield varieties,flowering habits and fruitgrowth were observed, and then pollen vigor in four developmental stages with different storageconditions [a) room temperature, b) room temperature and dry; c)4°C, d)4°C and dry; e)-70°C, and f)-70°C and dry] and were observed using the fluorochromatic reaction (FCR) method.And receptiveperiod of female flowers and pollinated affinity were studied by means of pollination techniques ofemasculation-bagging.The main results are as follows:1.The female flower buds was outer differentiation，that was flower buds germination of newbranches in the year after the formation female inflorescence and female flower．The male inflorescencelocated in its base.Bud swell and outer scale was shed on Mar.24th and Inner scale split and revealinggreen tips of shoot late March,Then pinnately compound leaf was spread and inner scale split withstraight catkin groups in early April.After20days,the leaf reached a maximum area.The growth ofshoot, compound leaves and leaflets were suit for "S" curve which grew highly significance fitting withLogistic growth model.Through correlation analysis, the growth of shoot, compound leaves and leafletswere significantly positively related to effective accumulated temperature.2.Mature pecan trees were monoecious,and bear male and female flower at different location onthe same tree.Female flowers were borne in a spike at the end of the current season’s shoot from latemarch to late April.As female flowers mature,the stigmatic go through four steps:stigma angle less than45°(Type I), stigma angle between45°and90°(Type II), stigma angle greater than90°(Type III) andthe stigma turn brown (Type IV).Stigmatic surfaces remain recepitive for7-9days.Results showed thatthe fruit set of treatments had significant differences between stigma Type I-IV.And the best stigmapollination for female flowers was Type III,which fruit set was18.08%.In addition,the results showedthat the fruit set of treatments had no significant differences on June1st and July2th,but the significantdifferences appeared on July31th.3.Pollination range over early pollen shed,heavy shed and end of pollen shed.Powder period waevery short, only for2-3days.The sequence for pollen viability was beginning of shedding> earlyshedding> heavy shedding> final shedding with storage durability for the pollen having the same order.Pollen viability for different storage conditions followed decay curves, but differences were noted with-70°C and dry>-70°C>4°C and dry>4°C> room temperature and dry> room temperature. Also,as storage time increased, pollen viability gradually decreased.4.A stigma of the female flower in the receptive period after pollination showed wave crests andpapillary cells at the top of the carpel.Pollens germinated on the stigma after pollinated4hours.Thenmany pollens germinated on the stigma and pollen tubes grown toward ovary after pollinated12 hours.Pollen began collapse after pollinated24hours and pollen tubes began collapse and papillary cellsat the top of the carpel began depression and collapse after pollinated3days.The fruits of growth anddevelopment is divided into the slow growth period,nuts rapid expansion period,the stone hardeningstage period, nuts grow period and the fruit maturity period.The growth of fruit length and width weresuit for "S" curve which grew highly significance fitting with Logistic growth model.The first fruit dropphenomenon occurs between early June to end of June,which dropping rate was16.27%of the totalfruits.The second flower fruit drop occurs between early July to Mid-June,which dropping rate was68.75%.The third time in August,which dropping rate was2.2%．5.The analysis of fruit setting pollinated under different kind pollens showed that the fruit settingof Mahan×No.35is highest by25.71%.Fruit quality of progeny test showed that the influence of fruitweight, fruit length, fruit width, the rate of seed, the seed diameter and shell thickness had no significantdifference.But the single seed weight and seed length had significant difference.And the nutrient contentof nut was also showed difference by oil,protein,soluble sugar and starch content test.Summarizedevaluation,No.35,Caddo, No.6and No.36were suitable for Mahan pollination varieties because of theirhigh production and good quality then others.