Morphology and density of trichomes and stomata of Trichosanthes cucumerina (Cucurbitaceae) as affected by leaf age and salinity

We investigated the relationship between leaf age and trichome/stomata densities in the snake tomato (Trichosanthes cucumerina L.). In a second experiment, the effects of different salinity levels on trichome and stomatal densities and their micromorphology were investigated. The leaf age investigation utilised young, semiold, and old leaves, while the salinity study utilised 0, 60, 120, and 180 mM NaCl for the investigation. Two morphotypes (Variant A-Green and Variant B-Light Green) of T. cucumerina were used for the salinity experiment while only Variant B-Light Green was used for the leaf age investigation. This study identified 2 discernible types of trichomes in T cucumerina, namely conical trichomes and globular-headed trichomes, which are segmented into 3 or more distinct sections. A major observation in this study was that while salinity did not significantly (P >= 0.05) affect the densities (abaxial and adaxial) of the conical trichomes in Variant A, the same parameter was significantly reduced in Variant B due to salinity treatment. Results showed that there were significantly (P >= 0.05) more stomata on the abaxial surface than the adaxial surface, irrespective of the morphotype and salinity treatment. Under the control treatment (no salinity), Variant B-Light Green had significantly more stomata on the abaxial side than Variant A-Green, while on the adaxial side, the reverse was found to be true. Results also showed that the conical and globular-headed trichomes' densities decrease as leaf age increases. The leaf petioles of the 2 variants are dominated by globular-headed trichomes. On the abaxial surface, analyses showed that there were 28% and 58% more stomata on the young leaf compared to semiold and old leaves, respectively. Further studies into the physiologically mediated mechanisms that are responsible for these observations in T. cucumerina are crucial.