Calcium,potassium and magnesium nutrition and their interactions in ‘Cox's Orange’ apple trees

Interactions between calcium (Ca), potassium (K) and magnesium (Mg) in apple tree nutrition were investigated in a pot experiment with ‘Cox's Orange’. Trees low in Ca supply were strongly dependent on Mg supply. Without Mg there was a very early and total leaf-fall. This led to a considerable yield response of Mg supply. During Ca deficiency, application of K enlarged the deficiency, resulting in a reduced K effect. Application of K reduced the Ca concentration in the leaves and Mg application depressed it further. This was not the case in the fruits, where K supply alone decreased the Ca concentration, while Mg supply, together with K, to some extent increased it. Spraying three times with MgSO₄·7H₂O, 1% or 2%, confirmed that fruit Ca is reduced by spray-applied Mg.     

Effects of ancymidol and gibberellins A3 and A4+7 on Tulipa gesneriana L. cv. Paul Richter during development in the greenhouse

The influence of soil drench applications of ancymidol (0.5 mg), GA₃ (25 mg), and Ga₄₊₇ (25 mg) was determined on the growth and development of the tulip under greenhouse conditions. Ancymidol applied on greenhouse day 1 or 6 significantly reduced the total length of the scape. Maximum reduction in growth occurred in the first internode, with a declining effect on internodes 2, 3 and 4. GA₄₊₇ applied simultaneously with ancymidol completely reversed the ancymidol effects. GA₃ was relatively ineffective. Compared to control plants, ancymidol reduced the number of cell divisions in the first internode, but not in the fourth internode. Cells of ancymidol treated plants were reduced in length and exhibited greater radial expansion. Ancymidol reduced the fresh weight of the stem and tended to conserve the fresh weight of the mother scales. The effect on the leaves and roots was variable. Ancymidol tended to increase the fresh weight of the daughter bulblets. There was no significant effect of ancymidol or the GA's on floral morphology or the number of days to flower in the greenhouse.     

Fruit quality in ‘Cripp's Pink’ apple,especially colour,as affected by preharvest sprays of aminoethoxyvinylglycine and ethephon

‘Cripp's Pink’ apple grown in Western Australia often develops poor colour at commercial harvest resulting in economic losses. To determine if fruit colour could be improved without advancing ripening, ‘Cripp's Pink’ apple fruit on trees were sprayed with aminoethoxyvinylglycine (AVG) alone, ethephon alone, or AVG followed by ethephon. The experiments were conducted at two different locations in Western Australia in 2002 and 2003. Fruit sprayed with AVG alone had retarded colour development at harvest. However, ethephon applied after AVG enhanced percent red blush, anthocyanin concentration and reduced chlorophyll concentration in the fruit skin in both locations. These fruit had similar colour to those treated with ethephon alone. Internal ethylene concentration and fruit firmness were unaffected by the different treatments in 2002. However, in 2003 AVG with or without ethephon reduced internal ethylene concentration and maintained firmness compared to ethephon alone. In conclusion, AVG treatment alone delayed colour development and ripening of ‘Cripp's Pink’, while AVG application 5 weeks before harvest followed by an ethephon application 2 weeks later enhanced red colour at commercial harvest. This is, therefore, an effective tool for improving colour of ‘Cripp's Pink’ apples at commercial harvest without adversely affecting other fruit quality attributes.     

Sennoside content and yield attributes of Cassia angustifolia Vahl. as affected by NaCl and CaCl2

Pot culture experiments were conducted to assess the extent of growth, photosynthetic capacity, sennoside concentration and yield attributes of Senna plant under the individual as well as combined influence of NaCl and CaCl₂. Six treatments, i.e. NaCl (80 and 160 mM), CaCl₂ (5 and 10 mM) alone and a combination of NaCl + CaCl₂ (80 + 10 and 160 + 10 mM) were given to the growing Senna plants at pre-flowering (45 DAS), flowering (75 DAS) and post-flowering (90 DAS) stages. Significant reductions were observed in pod biomass, leaf area, stomatal conductance, photosynthetic rate and sennoside concentration and yield, with each NaCl treatment. On the contrary, individual CaCl₂ treatments had a favourable effect. Under the effect of combination treatments, although these parameters were reduced, the extent of reduction was much less than one caused by NaCl treatments. The combined treatments thus mitigated the adverse effects caused by NaCl.     

Effects of dose and time of application of GA4+7 on russeting,fruit set and shape of ‘Golden Delicious’ apples

GA₄₊₇ concentrations, treatment date, number and frequency of treatments were factorially combined to determine their effects in preventing russeting of ‘Golden Delicious’ apples.The greatest reduction of russet was obtained by treating fruitlets 8 or 15 days after full bloom.Optimum timing and number of treatments provided better control of russet than high concentrations of gibberellins, although in some cases, higher doses improved russet control.Length of pedicel and ratio of longitudinal to transversal diameter were greater where russeting was reduced, and significant correlations were observed between fruit and pedicel length, and russeting. GA₄₊₇ treatments also affected setting, and in many cases caused parthenocarpy.