Re: why do trees need to grow straight in order to absorb water?

Trees do not need to grow straight to conduct water. Woody vines do it 
effectively and can be very contorted.  The path of water is not through a 
single tube, but through a series of xylem elements. In nearly all trees 
these elements are not arranged in a strictly vertical pattern but are 
offset from one another giving rise to a spiral pattern of water flow.  The 
water flows largely due to suction from above, not due to capillary flow.  
Often times the cohesive strand of water will break,  Recent research 
suggests that these breaks may be repaired overnight when the plant is 
under less water stress, for if the breaks were not repaired, tall trees 
would die due to lack of water.  Check a good plant physiology book for 
more details on this.