干旱区生态环境知识资源中心

Short-shoot leaves on the terminal stem segments of the drought-deciduous desert shrub ocotillo (Fouquieria splendens) are retained long after long-shoot leaves are lost through senescence and abscission. This formerly unreported observation has relevance for determining whether a terminal stem segment is new or old, because newly produced segments are routinely associated with the presence of long-shoot leaves. It is now clear that the absence of long-shoot leaves on a terminal stem segment cannot be used as unequivocal evidence that the segment is old. The relatively rapid loss of long-shoot leaves from new terminal stem segments may be an adaptation to reduce herbivory by accelerating maturation of the spine that develops from tissues left by each senescing long-shoot petiole.