Seed germination and early seedling growth behavior of critically endangered Catamixis baccharoides to variation in soil type

Catamixis baccharoides Thoms. is a critically endangered chasmophytic shrub endemic to northern India, particularly Haryana, Himachal Pradesh, Uttarakhand, and Uttar Pradesh, as well as in western Nepal. The germination and early seedling growth of C. baccharoides were studied in response to three different soil types; sandy soil, normal field soil, and mixed soil (1:1 of normal field soil and compost). Germination properties of seeds were examined for percentage germination, mean germination time, seed vigour index, peak value, and seed mortality, while growth parameters were determined after 10 weeks of germination for shoot length, root length, total plant length, root/shoot ratio, and leaf numbers. Seeds sown in sandy soil recorded the maximum (47.92%) mean germination rate, while least percentage germination was recorded for the mixed soil (5.83%). The sandy soil had the highest seed vigour index (447.54) and peak value (2.32), while mixed soil had the lowest values (32.46 and 0.29, respectively). Seed mortality index was highest in mixed soil (327.54), and lowest (181.16) in sandy soil. This study also revealed that seeds germinated in sandy soil had the lengthiest mean root length (4.37 cm), shoot length (5.00 cm), total plant height (9.37 cm), and maximum leaf numbers (6.67). Normal field soil had highest root/shoot ratio (1.05), succeeded by sandy soil (0.92) and mixed soil (0.89). Thus sandy soil assured optimal seed germination, establishment and growth in C. baccharoides offering an ex-situ conservation strategy for this monotypic shrub.