Physiological Studies On Vegetative Propagation Of Some Citrus Rootstocks:

Attia Ibrahim Ibrahim

This study was carried out during two consecutive seasons of 1992 and1993 on four citrus rootstocks namely: Volkamer lemon, Mexican lime,Cleopatra mandarin and Rangpur lime at the Experimental orchard ofHorticultural Research Institute at Giza : Selected trees for this investigation were 22-year- old, except for Volkamer lemon (8-year -old). They received regularity the normal Horticultural practices.Hardwood cuttings were prepared from one- year- old branches.Cuttings of about 10-12’ em long and 1-1.5 ern in diameter were prepared atthree dates namely mid-March, mid-June and mid-September. Leaves on eachcuttings were removed except only one leaf was left at the apex of cutting.However, just before planting the cuttings were grouped into two groups asfollows: (a) First group : The basal end of the cuttings at about 5 ern wasdipped for 5 seconds in tap water ”general control” or one of indole butryic acid solutions at 2000, 4000, 6000, and 8000 PPM. (b) The second group: The basalend of cuttings were wounded (about one inch) by making 2 incisions. Thecuttings were dipped in tap water ”control” or one of indole butyric acid solutions 2000, 4000, 6000 and 8000 PPM. The treated cuttings were immediately planted at a depth of 5 ern in plastic flats (32 em length x 25 em width x 15 cm height) filled with a mixture of sand and peat moss at 2 : I(v/v). The flats were kept for 60 days in a shade house under intermittent mist, operating during days house according to seasonal and daily weather conditions, within a range of 2.5 - 5.0 minutes between sprays and 5-15 seconds of mist duration. Thus, the study of each citrus rootstocks is considered a factorialexperiment .consisted of 30 treatments (three planting dates x five IBAconcentrations x two wounding treatments) . The treatments were arranged in acompletely randomized block design with four replicates for each treatment andeach replicate included ten cuttings . The obtained results could be summarizedas follows : 5-1- Rooting of citrus rootstock cuttings : Generally, mid-September proved to be the most appropriate time forpreparing and planting stem cutting of the studied citrus rootstocks: Volkamerlemon, Mexican lime, Cleopatra mandarin and Rangpur lime rather than mid-June or mid- March planting. In addition, wounding the basal ends of thecutting, enhanced all the studied rooting parameters(rooting percentage, number of adventitious roots per cutting and root fresh and dry weight parameters).Also, dipping the basal ends of cuttings in indole butyric acid solutions at 2000, 4000, 6000 or 8000 ppm for five seconds increased the rooting ability of thecuttings particularly, 8000 PPM IBA. Furthermore, the stimulating effect ofthe studied factors (planting date, IBA and wounding was increased when theyused in combinations whether in double combination (planting date x wounding,~ planting date x IBA or wounding x IBA) or trible combination (plating date x wounding x IBA )Conclusively, planting citrus rootstocks cuttings in mid-September afterwounding and treating with IBA at 8000 ppm gave the highest rootingpercentage 5-2 Chemical study : 5-2-l-Total soluble indoles and phenolsIn general, planting date had significant effect on totals indoles andphenols of cuttings . Shortly, planting Volkamer lemon, Mexican lime,Cleopatra mandarin and Rangpur lime cuttings in mid- September increasedcutting content total soluble indoles and decreased its content of total soluble phenols as compared with those planted either in mid-March or mid-June.5-2-2- Total carbohydrates and nitrogen content. The highest total carbohydrates and nitrogen content were shown in Volkamer lemon cuttings prepared and planted in mid-September followed bymid- March planting. While, those planted in mid-June showed be the lowestvalues in this respect. Generally, total carbohydrates and nitrogen content of Mexican lime, Cleopatra mandarin and Rangpur lime cuttings took similar trend to that ofVolkamer lemon.Anatomical study : Histological study reveals that the preformed root initials were noticed inthe cortex of the four studied citrus rootstocks under investigation. Root initials were raised from cambuim zone. Moreover, cambium was activated in all IBAtreated cuttings, particularly, when IBA was supplemented by woundingtreatment. Generally, the results showed that treating the wounded cuttings ofVolkamerlemon, Mexican lime and Cleopatra mandarin as well as Rangpur lime withIBA at 4000,6000 and 8000 PPM improved the studied rooting parameters. Onthe other hand, treating wounded cuttings with IBA and planting in mid-September proved to be the most effective treatments in enhancing rooting parameters (rooting percentage, number of roots per cutting fresh and dry weight of roots per cutting) as compared with the analogous ones planted in mid-March or mid-June.