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High yields of protoplasts were isolated from embryogenic suspension cultures of Rosa persica × xanthina

Plantlets of Vitis vinifera L. `Moscato Bianco' were grown in vitro in cellulose plugs (Sorbarods) saturated with a modified Murashige and Skoog rooting medium. Both the inclusion of 0.5-l mg paclobutrazol/liter in the rooting medium and the use of culture vessels that reduce the relative humidity from 100% to 94% improved resistance of plantlets to wilting after transplanting. Maximum benefit was obtained with a combination of paclobutrazol and reduced humidity; it resulted in smaller stomatal apertures, shorter stems, reduced leaf area, and more and thicker roots. Chemical names used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl) pentan-3-01 (paclobutrazol).

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Plantlets cultured in vitro on agar-based media in a water-saturated atmosphere wilt rapidly when transferred to normal greenhouse or field conditions. Water is rapidly lost from the leaves because stomata fail to respond to those stimuli that normally induce closure (1-4), and poor development of epicuticular wax results in loss of water through the cuticle (5-7). Uptake of water by the roots is limited by damage incurred during transplantation and by poor contact with the substrate. Problems of transplantation are accentuated in vitrified plantlets, which grow slowly and wilt rapidly. Reduced deposition of cellulose and lignin in these plantlets causes reduced cell wall pressure, leading to increased water uptake by the cells and a glassy turgescence of leaves and stems (8,9).

The determination of rates of macroalgal growth and productivity via temporal fresh weight (FW) measurements is attractive, as it does not necessitate the sacrifice of biomass. However, there is no standardised method for FW analysis; this may lead to potential discrepancies when determining growth rates or productivity and make literature comparison problematic. This study systematically assessed a variety of lab-scale methods for macroalgal FW measurement for growth rate determination. Method efficacy was assessed over a 14-day period as impact upon algal physiology, growth rate on basis of FW and dry weight (DW), nitrate removal, and maintenance of structural integrity. The choice of method is critical to both accuracy and inter-study comparability of the data generated. In this study, it was observed that the choice of protocol had an impact upon the DW yield (P values = 0.036-0.51). For instance, those involving regular mechanical pressing resulted in a >25% reduction in the final DW in two of the three species studied when compared to algae not subjected to any treatment. This study proposes a standardised FW determination method employing a reticulated spinner that is rapid, reliable, and non-destructive and provides an accurate growth estimation.