The effect of salinity (50, 100 and 150 mM NaCl) on seed germination and early growth of two Palestinian tomato (Solanum lycopersicon) cultivars (J1 and Ram) was investigated. Salinity delayed seed germination of both cultivars, and none of them reached 50% germination at 150 mM NaCl even after 21 days of incubation. The seedling height increased with time but decreased with increasing salinity level in both cultivars. Ram cultivar showed higher relative seedling height and higher relative root length than the J1 cultivar. The development of root system and leaves was reduced as salinity increased. Salt stress caused reduction in the vascular system in both root and stem. Meanwhile, salinity stress resulted in an increase in the thickness of the cortex region of the stem and a reduction in that of the root. The reduced severity of morphological and anatomical deformations observed in the Ram line is more tolerant to salinity stress than the J1 cultivar, during the early growth stage.
Phytohormones and their interactions play critical roles in Solanum tuberosum (potato) tuberization. The stimulatory role of jasmonic acid (JA) in tuber development is well established because of its significant promotion of tuber initiation and tuber bulking. However, the dynamics and potential function of JA signalling in potato tuberization remain largely unknown. The present study investigated the role of the JAZ1 subtype, a suppressor of JA signalling, in potato tuberization. Using 35S:StJAZ1-like-GUS as a reporter, we showed that JA signalling was attenuated from the bud end to the stem end shortly after tuber initiation. Overexpression of StJAZ1-like suppressed tuber initiation by restricting the competence for tuber formation in stolon tips, as demonstrated by grafting an untransformed potato cultivar to the stock of StJAZ1-likeoverexpressing transgenic potato plants (StJAZ1-like ox). In addition, transcriptional profiling analysis revealed that StJAZ1-like modulates the expression of genes associated with transcriptional regulators, cell cycle, cytoskeleton and phytohormones. Furthermore, we showed that StJAZ1-like is destabilised upon treatment with abcisic acid (ABA), and the attenuated tuberization phenotype in StJAZ1-like ox plants can be partially rescued by ABA treatment. Altogether, these results revealed that StJAZ1-like-mediated JA signalling plays an essential role in potato tuberization.
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