PJB-2020-469
Morphological and Cytological Changes during the Shoot Degradation of Phyllostachys edulis ‘Pachyloen’
Wanqi Zhao
Abstract
Bamboo shoot degradation is a widespread phenomenon that can lead to bamboo forest loss and affect the sustainable management of bamboo forests. However, identifying degrading shoots is a major challenge, as little is known about the cytological mechanisms underlying the formation of shoot degradation. Our observations revealed that the absence of guttation was the most reliable feature for distinguishing degraded shoots from normal shoots of Phyllostachys edulis ‘Pachyloen’ in the early stage. In the midterm stage, the morphology of the sheaths was the most reliable feature, and by the later stages, degrading shoots were readily apparent. During the process of degradation, the nucleus gradually condensed, degraded, and displayed the characteristics of cell death; the cell wall became loose and was often damaged; the silicon cells in the epidermal layer increased; and the rapidity of starch degradation increased. Changes in five major endogenous hormones—indole acetic acid (IAA), gibberellic acid (GA), zeatin riboside (ZR), brassinolide (BR), and abscisic acid (ABA)—in Ph. edulis ‘Pachyloen’ degraded shoots were also studied. Compared with normal bamboo shoots, the content of ABA in degraded shoots increased significantly, especially in the later stage, which was eight times greater than that in normal shoots. Endogenous hormone contents in different parts of degraded shoots differed from the endogenous hormone contents in normal shoots. Moreover, the ratio of (IAA+ZR +BR+ GA3)/ABA in degraded shoots gradually decreased, which promoted the degradation of shoots. These results established a comprehensive criterion for identifying degraded bamboo shoots that could be used to ensure that bamboo shoots are salvaged in a timely manner. Furthermore, our findings provide new insight into the cytological characteristics of degraded bamboo shoots, including the mechanisms underlying the degradation of bamboo shoots.
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