Differential responses of double petal and multi petal jasmine to shading: II. Morphology, anatomy and physiology

We compare the morphological, anatomical, developmental and physiological and biochemical responses of a double petal (DP) type jasmine (Jasminum sambac Aiton) to shading with a multi petal (MP) one. In both types, plant height, internode length, leaf size and leaf relative water content were all increased by shading, while leaf tissue density, reproductive development and the number of flowers decreased. Shaded leaves produced fewer but larger mesophyll and vein vascular cells. The total protein contents in shaded leaves were higher than those in non-shaded leaves for a shading period of 21 d (DP type) and 14 d (MP type), but thereafter they fell below the levels found in leaves exposed to full sunlight. Under shading, both peroxidase (POD, EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) activities were induced, catalase (CAT, EC 1.11.1.6) activity was repressed, and that of ascorbate peroxidase (APX, EC 1.11.1.11) was irregular. Total soluble sugar and malondialdehyde contents in both types were significantly reduced by shading. The results showed that DP jasmine overall tolerated shading better than the MP type, because of the former with more efficient photosynthetic and metabolic rates, reasonable allocation of photosynthates as well as higher contents of proteins and antioxidant enzymes. A moderate level and duration of shading (20-50% irradiance no longer than 28 d) was beneficial to jasmine plant growth, but extremely low (5% irradiance) and/or prolonged (>28 d) shading was detrimental to both vegetative growth and reproductive development and should be avoided, particularly in the plantation of MP type.

► The double petal jasmine type was more shade tolerant than the multi petal type. ► Shading delayed flowering, and disrupted flower development in the multi petal type. ► Shading increased leaf size, with larger but fewer mesophyll and vascular cells. ► Shading increased the activity of POD and SOD and reduced that of CAT. ► The content of soluble sugars and malondialdehyde was strongly reduced by shading.