Effect of microclimate and photosynthesis on strawberry reproductive growth in a greenhouse: using cumulative leaf photosynthesis as an index to predict the time of harvest

We evaluate whether cumulative photosynthesis (<i>A</i>_n,C) could predict the time of harvest in strawberry better than light (<i>I</i>_C) or temperature (<i>T</i>_a,C) as forecast indices. We monitored the daily dynamics of flowering, fruit set, and harvest in over 2,700 fruits across the growing season in a greenhouse in Japan. Photosynthesis was calculated using a biochemical model, and <i>A</i>_n,C calculated by totalling the cumulative rate from flowering to harvest in each fruit. <i>I</i>_C and <i>T</i>_a,C were calculated by totalling daily cumulative light intensity and average temperature. A new index (<i>D</i>) was defined as the normalised variation of <i>A</i>_n,C, <i>I</i>_C, and <i>T</i>_a,C, and a statistical analysis was conducted on the means for each index. The results showed that <i>A</i>_n,C had the lowest <i>D</i> (0.114), suggesting that it was a better index for predicting the time of harvest. This study suggests the importance of considering the accumulation of photosynthates in individual fruit, which cannot be achieved by <i>I</i>_C or <i>T</i>_a,C, these results can be used to improve the forecasting and optimisation of yield. However, further research is required to substantiate these claims.