Danilo Pina

Field performance of artificial seed-derived sugarcane plants

This study shows the behaviour of sugarcane plants cv. CP-5243 derived from artificial seed compared with traditional and isolated bud methods. Artificial seed-acclimatised plants were planted in field conditions simultaneously with two-control treatments previously germinated: macropropagated plants derived from stems of three buds and axillary buds isolated from field-grown plants. Plants from artificial seed were taller and had a smaller diameter at 8 months, but these differences disappeared at 12 months. With respect to sugar analysis and yield, no differences in all parameters evaluated were found between artificial seed-derived plants and plants derived from the two other methods.

PHOTOSYNTHESIS AND CARBON METABOLISM IN PLANTAIN (MUSA AAB) PLANTLETS GROWING IN TEMPORARY IMMERSION BIOREACTORS AND DURING EX VITRO ACCLIMATIZATION

SummaryThe photosynthetic capacity changes and the main enzymatic systems related to carbon metabolism were investigated during the in vitro culture of plantain shoots (Musa AAB cv. CEMSA 3/4) in temporary immersion bioreactors (TIB) and their subsequent acclimatization. The maximal rate of photosynthesis (Pn), transpiration, and the activity of the carbon metabolism enzymes phosphoenolpyruvate carboxylase (PEPC), acid invertase (AI), pyruvate kinase (PK) and sucrose phosphate synthase (SPS) were measured every 7 d during the 21 d of elongation in TIB, and the following 42 d of acclimatization. Sucrose content in the liquid medium and in the leaves was also determined. The most significant changes in plant growth were observed during acclimatization. During the in vitro stage photosynthesis was limited (4–6 μmol CO2m−2s−1); the photosynthetic rate however increases rapidly and significantly as soon as in vitro culture is over during acclimatization. PEPC activity increased during the whole evaluation period. The highest levels were achieved around days 42 and 56. PK and SPS activities were optimal during the first weeks in acclimatization (28–35 d), while AI increased at the beginning of the elongation phase (7 d), and later at the end of the acclimatization (49–63 d). The relationships between morphological parameters, photosynthetic capacity of the plantlets and the carbon metabolism enzymes during both phases of the culture are discussed.

GROWTH AND PHOTOSYNTHETIC ACTIVITY DURING ACCLIMATIZATION OF SUGARCANE PLANTLETS CULTIVATED IN TEMPORARY IMMERSION BIOREACTORS

Abstract Acclimatization of sugarcane plantlets (Saccharum spp. hybrid) var. C91-301, micropropagated in temporary immersion bioreactors, was studied. When in vitro plantlets were transferred to acclimatization conditions, photosynthesis increased only slightly during the first 7 d. After this period, the increase was constant with only a small decline after transfer to uncontrolled external conditions. Production of fresh and dry weights, number of leaves and roots, leaf area, stomatal density and chlorophyll contents were evaluated during the acclimatization period. From day 14 on, sugarcane plantlets exhibited low but positive photosynthesis due to the new formation of leaves and roots. The increase in light intensity and the gradual reduction of relative humidity during acclimatization did not constitute inhibitory factors, as can be interpreted from the increased photosynthetic activity until 21 d. Stomatal density and leaf area after 21 d were also increased, while the chlorophyll content declined.