Micro-variation in peach stem diameter and its relationship with soil water potential and meteorological factors.

In well-irrigated and gradual-drought pot experiments,micro-variations in "Shinvhong" peach stem diameter were con-tinuously monitored.Responses in maximum daily stem shrinkage(MDS),stem increase(DI),and stem diameter recovering time(RT) to soil water potential and meteorological factors were then analyzed and a suitable irrigation index established.The results show that when soil water potential decreases,RT and MDS increase while DI rapidly drops below zero.Meteorological factors have a notable impact on peach stem diameter.Factors including radiation and air relative humidity have the strongest impact on stem diameter.In fact continuous rainfall significantly affects DI and RT.DI is the most ideal irrigation indicator as it is very much influ-enced by soil water potential and less affected by meteorological factors.DI value of zero is probably the best irrigation threshold.MDS is strongly affected by meteorological factors and requires reference MDS under well-irrigated conditions.RT on the other hand is not significantly related with soil water potential.Therefore neither of these variables is suitable as irrigation index.