ROOT CORTEX DEATH AND SUBSEQUENT INITIATION AND GROWTH OF LATERAL ROOTS FROM BARE STELES OF CHICKPEAS

The anatomical responses of chickpea (Cicer arietinum L.) roots to agi ng and severe water deficits and their capacity for subsequent initiat ion and growth of new lateral roots after rewatering are only partiall y known. This study was conducted to characterize the degeneration of epidermal and cortical cells of chickpea roots and the subsequent init iation and growth of new roots from bare steles, i.e., steles surround ed by an endodermis but lacking other parts of the cortex. Chickpea pl ants were grown in pots in a greenhouse under standard culture conditi ons (potting mix and daily watering) or drought treatments. For drough t treatments, plants were grown in sand and exposed to repeated 10-d t reatments of water deficits and rewatering. In standard culture condit ions, older cortices collapsed and deteriorated but not simply as a fu nction of chronological age. After one 10-d drought treatment, the epi dermis and outer cortex of primary and some secondary and tertiary roo ts collapsed and after a subsequent rewatering treatment, the epidermi s and cortex deteriorated and sloughed from steles. In both standard a nd drought conditions, bare steles were able to sustain growing root t ips, indicating that the endodermis was effective in preserving stelar functions. In droughted plants, bare steles were able to initiate new lateral roots from the pericycle after rewatering, indicating that co rtical tissue other than the endodermis was not necessary for secondar y and tertiary chickpea roots to initiate new lateral roots. In a give n root system exposed to the drought treatments, although the cortex c ollapsed on some roots, the cortices of other secondary roots did not collapse or deteriorate under similar severe conditions. The reason fo r cortical survival is unclear, but the response of these roots was si milar to roots that have a suberized hypodermal layer which protects u nderlying cortical tissues from excessive drying.