Question

Stomata in pineapple remain closed during the day then how do they perform photosynthesis

Answer 1

In desert plants the stomata open at night.
They take in carbon dioxide at night, and is stored in the form of an intermediate which is used during day for photosynthesis (When the stomata are closed).
Also, chlorophyll of the plant are located in the stem as levesare reduced to spines and stem takes the function of photosynthesis. 

Answer 2

In desert plants the 'stomata' open at night. They take in carbon dioxide at night, and is stored in the form of an intermediate which is used during day for photosynthesis.
Therefore, the deserts plants grow in dry conditions. In such plants, carbon dioxide is taken up by the leaves on the green stem through stomata, which remain open in the night. However, during the day, the stomata remain closed to conserve moisture. These plants carry out photosynthesis without much loss of water.