Alternative Application of Plant Growth Regulators to Optimize Rooting in Citrus

In order to support ever increasing demands of scientific research; laboratory protocols must be examined, evaluated, and methods of possible improvement addressed experimentally. This experiment does  this by exploring an atypical method of using plant growth regulators to induce rooting of citrus cuttings more quickly than is usual. Fourteen apical cuttings (~ 15cm) were collected from 2-3 year old citrus rootstock varieties US 812 and Carrizo Citrange.  Each cutting was stripped of all but 2 leaves, and dipped for 20 minutes in one of 3 treatment rooting solutions of standard MS media with 20g/L sucrose, 0.5mg/L NAA, 5mg/L IBA, and 0.05mg/L spermidine.  Treatment A consisted of rooting solution without sucrose, treatment B without spermidine, and treatment C included both spermidine and sucrose.   A 4^th set of cuttings was dipped in DI water as a control.  The cuttings were first stuck in conical containers filled with damp, steam sterilized sand and then 5ml of rooting solution or water control was applied near the base of each cutting. Plastic bags were placed over each cutting and secured with a rubber band. Rooting data was collected once a week for 8 weeks.  Rooting solution was reapplied each week.  All plants were kept in controlled greenhouse conditions for the duration of the experiment. Overall, US 812 exhibited no rooting response to any of the treatment conditions within the time allotted during the project.    Carrizo rooted best in Treatment A (no sucrose), showing 57 % rooting success by week 4 and 71% by week 8.  This initial experiment has created many questions which provide an opportunity to make further examinations.  This could potentially result in further improvements of laboratory and greenhouse protocols that support research which relies on efficient and reliable plant propagation.