Effects of Drought and Heat on Photosynthetic Performance, Water Use and Yield of Two Selected Fiber Hemp Cultivars at a Poor-Soil Site in Brandenburg (Germany)

Abstract

Hemp currently regains certain importance as fiber, oil and medical crop not least because of its modest requirements of biocides, fertilizer and water. During recent years, crops were exposed to a combination of drought and heat, even in northern Central-Europe. Dynamic responses of photosynthesis and stomatal conductance to these stresses and their persistent effects had been studied, if at all, in controlled environment experiments. Comprehensive field studies on diurnal and long-term net photosynthesis and gas exchange, and yield properties of hemp during a drought prone, high-temperature season in northern Central-Europe are obviously missing. Thus, in whole season field trails, the essential actual physiological (rates of net photosynthesis and transpiration, stomatal conductance, water use efficiencies, ambient and internal CO2 concentrations) and the yield performance of modern high-yielding multi-purpose hemp cultivars, ‘Ivory’ and ‘Santhica 27’, were evaluated under extreme environmental conditions and highly limited soil water supply. This provides comprehensive information on the usability of these cultivars under potential future harsh production conditions. Plants of both cultivars differentially cope with the prevailing climatic and soil water conditions. While ‘Ivory’ plants developed high rates of CO2 gain and established large leaf area per plant in the mid-season, those of ‘Santhica 27’ utilized lower CO2 uptake rates at lower leaf area per plant most time. This and the higher germination success of ‘Santhica 27’ resulted in nearly twice the yield compared to ‘Ivory’. Although stomatal control of CO2 gain was pronounced in both cultivars, higher stomatal limitations in ‘Ivory’ plants resulted in higher overall intrinsic water use efficiency. Cultivation of both hemp cultivars with only basic irrigation during seed germination was successful and without large effects on yield and quality. This was valid even under extremely hot and dry climatic conditions in northern Central Europe.

Industrial hemp seed: from the field to value-added food ingredients

“…It has been shown to have a positive effect on the soil and can also be used for phytoremediation, particularly for the removal of heavy metals such as lead (Burczyk et al 2008 ). Although frequently touted as requiring low inputs, hemp requires large amounts of nitrogen input for good plant establishment and there are few studies into the impact that plant nutrition has on subsequent seed and fibre quality (Herppich et al 2020 ). There is sparse information on salinity tolerance of hemp across all growth stages (Cheng et al 2016 ; Hu et al 2018 ).…”

Establishment of the basidiomycete Fomes fomentarius for the production of composite materials

“…In contrast, hemp is a frugal but high-yielding plant that has no pesticide and low fertilizer demand but uses water about six times more efficiently for biomass formation than cotton [ 24 , 25 ]. Thus, hemp can grow well even under hot and dry conditions and on poor-soil sites such as prevalent in the Berlin-Brandenburg area and beyond [ 26 ]. The second main product after hemp fibre separation, the shives, are currently very often under-valued in applications like animal bedding.…”

Effects of short-term environmental stresses on the onset of cannabinoid production in young immature flowers of industrial hemp (Cannabis sativa L.)

“…Due to global warming, agricultural crops including Cannabis plants encounter multiplexed environmental stresses of which extreme heat and drought are the most impactful. Herppich et al 2020 showed that two fiber-type hemp varieties (‘Santhica 27’ and ‘Ivory’) responded differently against the combined stress. ‘Santhica 27’ utilized low CO 2 uptake rates in lower leaves and higher seed germination rates that resulted in twice the fiber yield compared to ‘Ivory’, whereas ‘Ivory’ developed high rates of CO 2 gain which enabled the establishment of large leaf area with more stomatal regulation, resulting in higher water use efficiency (Herppich et al 2020 ).…”

“…Herppich et al 2020 showed that two fiber-type hemp varieties (‘Santhica 27’ and ‘Ivory’) responded differently against the combined stress. ‘Santhica 27’ utilized low CO 2 uptake rates in lower leaves and higher seed germination rates that resulted in twice the fiber yield compared to ‘Ivory’, whereas ‘Ivory’ developed high rates of CO 2 gain which enabled the establishment of large leaf area with more stomatal regulation, resulting in higher water use efficiency (Herppich et al 2020 ). As seen in this study, fiber hemp promptly reprogramed their photosynthetic rate, transpiration, stomatal regulation, and water use efficiency upon treatment of environmental stresses, affecting the yield performance, which affects the total content and potentially the ratios of secondary metabolites in Cannabis .…”