Abstract
To study the effects of shading level on the photosynthesis and corm weight of konjac plant, the chlorophyll fluorescence parameters, daily variation of relative electron transport rate (rETR), net photosynthetic rate (Pn), and corm weight of konjac plants under different treatments were measured and comparatively analyzed through covered cultivation of biennial seed corms with shade nets at different shading rates (0%, 50%, 70%, and 90%). The results showed that with the increase in shading rate, the maximum photochemical efficiency, potential activity, and non-photochemical quenching of photosystem Ⅱ (PSⅡ) of konjac leaves constantly increased, whereas the actual photosynthetic efficiency, rETR, and photochemical quenching of PSⅡ initially increased and then decreased. This result indicated that moderate shading could enhance the photosynthetic efficiency of konjac leaves. The daily variation of rETR in konjac plants under unshaded treatment showed a bimodal curve, whereas that under shaded treatment displayed a unimodal curve. The rETR of plants with 50% treatment and 70% treatment was gradually higher than that under unshaded treatment around noon. The moderate shading could increase the Pn of konjac leaves. The stomatal conductance and transpiration rate of the leaves under shaded treatment were significantly higher than those of the leaves under unshaded treatment. Shading could promote the growth of plants and increase corm weight. The comprehensive comparison shows that the konjac plants had strong photosynthetic capacity and high yield when the shading rate was 50%-70% for the area.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Highlights
Konjac is the general name of perennial herbs of the Genus Amorphophallus Blume, Family Araceae
This result indicates that a certain degree of shading can improve chlorophyll fluorescence parameters and enhance the photosynthetic efficiency of konjac plant leaves
ΦPSII refers to the actual quantum yield of photosystem II (PSII), reflecting the actual photosynthetic efficiency (Genty et al, 1989). relative electron transport rate (rETR) refers to the relative rate of photosynthetic electron transport of PSII, which represents the photosynthetic rate (Bjorkman and Demming, 1987). qP refers to fluorescence quenching caused by photosynthesis, namely the proportion of the energy adsorbed by PSII for photochemical reaction, which reflects photosynthetic activity
Summary
Konjac is the general name of perennial herbs of the Genus Amorphophallus Blume, Family Araceae. Amorphophallus konjac, is widely distributed in the south of Qinling Mountains, China, to the Himalaya Range in the west, Japan in the east, and Indochina Peninsula in the south (Liu, 2004). Konjac contains a large amount of glucomannan, which has unique physiological functions and physical and chemical properties. It is widely used in food processing, medical and health care, environmental protection, chemical industry, and other fields (Zhang et al, 2005; Chua et al, 2010). How to increase the yield of konjac by a large margin is an urgent problem to be solved
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